@article{diether_hulshof_willing_kempen_2023, title={A blend of medium-chain fatty acids, butyrate, organic acids, and a phenolic compound accelerates microbial maturation in newly weaned piglets}, volume={18}, ISSN={["1932-6203"]}, url={https://doi.org/10.1371/journal.pone.0289214}, DOI={10.1371/journal.pone.0289214}, abstractNote={Inclusion of additive blends is a common dietary strategy to manage post-weaning diarrhea and performance in piglets. However, there is limited mechanistic data on how these additives improve outcomes during this period. To evaluate the effects of Presan FX (MCOA) on the intestinal microbiota and metabolome, diets with or without 0.2% MCOA were compared. Pigs fed MCOA showed improved whole-body metabolism 7 days post-weaning, with decreased (P < 0.05) creatine, creatinine and β-hydroxybutyrate. Alterations in bile-associated metabolites and cholic acid were also observed at the same time-point (P < 0.05), suggesting MCOA increased bile acid production and secretion. Increased cholic acid was accompanied by increased tryptophan metabolites including indole-3-propionic acid (IPA) in systemic circulation (P = 0.004). An accompanying tendency toward increased Lactobacillus sp. in the small intestine was observed (P = 0.05). Many lactobacilli have bile acid tolerance mechanisms and contribute to production of IPA, suggesting increased bile acid production resulted in increased abundance of lactobacilli capable of tryptophan fermentation. Tryptophan metabolism is associated with the mature pig microbiota and many tryptophan metabolites such as IPA are considered beneficial to gut barrier function. In conclusion, MCOA may help maintain tissue metabolism and aid in microbiota re-assembly through bile acid production and secretion.}, number={7}, journal={PLOS ONE}, author={Diether, Natalie E. and Hulshof, Tetske G. and Willing, Benjamin P. and Kempen, Theo A. T. G.}, editor={Tomaszewska, EwaEditor}, year={2023}, month={Jul} }
 @article{kempen_zijlstra_2023, title={Eat like a Pig to Combat Obesity}, volume={13}, ISSN={["2218-1989"]}, DOI={10.3390/metabo13030420}, abstractNote={Obesity and related metabolic health issues are a growing human threat, with many theories regarding its causes. In swine, physiologically alike to humans, considerable knowledge on obesity mechanisms has been accumulated. Calorie counting is the basis for managing swine diets and applied with great accuracy. Epigenetic programing predisposes pigs to insulin insensitivity, but pigs seem to sense this insensitivity and consequently eat less, preventing obesity. Pigs naturally prefer to eat small breakfasts and large dinners. Deviating from this eating pattern or providing diets with a high glycemic burden can trigger obesity; however, pigs will restrict food intake to prevent serious obesity. Interestingly, in practice, problems with obesity are rarely seen, even when pigs are fed poorly timed diets similar to junk food, likely because swine diets are balanced for every nutrient. Indeed, feeding pigs diets deficient in micronutrients does trigger obesity. For humans, several micronutrient requirements have not been set officially, and diets optimized for all micronutrients are rarely provided. In conclusion, various obesity triggers are being debated for humans, which have been proven in swine. Obesity problems in pigs are nevertheless less excessive, likely because pigs recognize unhealthy eating practices and consequently reduce food intake to avoid serious complications. Finally, swine diets are normally balanced for all nutrients, which may be an important practice to prevent obesity, from which human health could greatly benefit.}, number={3}, journal={METABOLITES}, author={Kempen, Theo A. T. G. and Zijlstra, Ruurd T. T.}, year={2023}, month={Mar} }
 @article{kempen_boerboom_2023, title={Is the intestinal mucous layer a natural deep eutectic solvent-based digestion matrix?}, volume={324}, ISSN={["1522-1547"]}, url={https://doi.org/10.1152/ajpgi.00006.2023}, DOI={10.1152/ajpgi.00006.2023}, abstractNote={ In plants, a third solubilization matrix (besides water and lipids) has been proposed, composed of natural deep eutectic solvents (NADESs). Such matrices allow for the solubilization of many biologically important molecules, such as starch, which are insoluble in water or lipids. NADES matrices also support enzyme activity, such as amylase, at higher rates than water or lipid-based matrices. We contemplated if a NADES environment could play a role in small intestinal starch digestion. The intestinal mucous layer (encompassing both the glycocalyx and the secreted mucous layer) has a chemical composition that fits well with NADES (e.g., glycoproteins with exposed sugars, amino sugars, and amino acids like proline and threonine, as well as quaternary amines like choline and ethanolamine and organic acids like citric and malic acid). Various studies have indeed shown that amylase binds to glycoproteins within the mucous layer of the small intestine where it performs its digestive action. Dislodging amylase from these binding sites impedes starch digestion and it may well cause digestive health problems as a result. Hence, we propose that the mucous layer in the small intestines harbors digestive enzymes like amylase, while starch, due to solubility, redistributes from the lumen into the mucous layer where it is subsequently digested by amylase. The mucous layer would thus constitute a NADES-based digestion matrix in the intestinal tract. }, number={6}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY}, author={Kempen, Theo A. T. G. and Boerboom, Gavin M.}, year={2023}, month={Jun}, pages={G438–G441} }
 @article{boerboom_navarro-villa_kempen_2023, title={Metabolomic Analysis of Wooden Breast Myopathy Shows a Disturbed Lipid Metabolism}, volume={13}, ISSN={["2218-1989"]}, DOI={10.3390/metabo13010020}, abstractNote={Myopathies have risen strongly in recent years, likely linked to selection for appetite. For white striping (WS), causes have been identified; but for wooden breast (WB), the cause remains speculative. We used metabolomics to study the breast muscle of 51 birds that were scored for both at 35 days of age to better understand potential causes. A partial least square discriminant analysis revealed that WS and WB had distinct metabolic profiles, implying different etiologies. Arginine and proline metabolism were affected in both, although differently: WB increased arginine in breast muscle implying that the birds did not use this pathway to increase tissue blood flow. Antioxidant defenses were impeded as shown by low anserine and beta-alanine. In contrast, GSH and selenium concentrations were increased. Serine, linked to anti-inflammatory properties, was increased. Taurine, which can stabilize the cell’s sarcolemma as well as modulate potassium channels and cellular calcium homeostasis, was also increased. Mineral data and depressed phosphatidylethanolamine, cAMP, and creatine-phosphate suggested compromised energy metabolism. WB also had drastically lower diet-derived lipids, suggesting compromised lipid digestion. In conclusion, WB may be caused by impaired lipid digestion triggered by a very high appetite: the ensuing deficiencies may well impair blood flow into muscle resulting in irreparable damage.}, number={1}, journal={METABOLITES}, author={Boerboom, Gavin M. and Navarro-Villa, Alberto and Kempen, Theo A. T. G.}, year={2023}, month={Jan} }
 @misc{kempen_hulshof_gerrits_zijlstra_2023, title={Review: The amazing gain-to-feed ratio of newly weaned piglets: sign of efficiency or deficiency?}, volume={17}, ISSN={["1751-732X"]}, DOI={10.1016/j.animal.2023.100987}, abstractNote={Shortly after weaning, piglets generally eat dry feed poorly; but nevertheless, a phenomenal gain-to-feed ratio is achieved as they gain about as much weight as they eat (150-200 g/d). The high gain-to-feed ratio, though, cannot be explained by their nutrient intake or nutrient repartitioning. Analyses based on tissue composition and bio-electrical impedance data showed that newly weaned piglets lose fat, maintain protein, and gain large amounts of water because of edema. This edema, which may well contribute up to one kg of BW, seems to be triggered by refeeding syndrome. Refeeding syndrome in adult humans occurs when subjects fast for an extended period of time (weeks) that results in downshifts in metabolic activity and concomitant shedding of phosphate (PO4), magnesium (Mg), and potassium (K) in urine. If food is abruptly reintroduced, thus, resulting in strong insulin spikes, metabolism is triggered but hampered by a lack of PO4, Mg, K, and thiamine, causing hypophosphatemia, metabolic stress, and edema. In piglets, the same process appears to happen immediately after weaning but in hours rather than weeks, possibly linked to their high metabolic rate. Refeeding syndrome can be lethal in humans but does not appear to be directly lethal in piglets. Our attempts to prevent it through altered diet composition and/or controlled feeding programs have not resulted in better performance at the end of the nursery phase. A practical ramification of weaning-induced edema is that growth and gain-to-feed ratio data immediately after weaning should be interpreted with caution. In addition, diets arguably should be formulated to not strongly trigger insulin release, while high lysine levels are not needed as the gain is not based on protein accretion.}, number={11}, journal={ANIMAL}, author={Kempen, Theo A. T. G. and Hulshof, Tetske G. and Gerrits, Walter J. J. and Zijlstra, Ruurd T.}, year={2023}, month={Nov} }
 @article{hees_chiers_hartog_kempen_maes_millet_janssens_2023, title={Supplementing oat hulls to the diet of suckling piglets altered their intestinal tract and colonic microbiota development}, volume={12}, ISSN={["2405-6545"]}, url={https://doi.org/10.1016/j.aninu.2022.10.002}, DOI={10.1016/j.aninu.2022.10.002}, abstractNote={Current study evaluated the effect of a fine and coarsely ground insoluble dietary fibre source on the gastrointestinal development of suckling pigs. Oat hulls (OH) were selected as a model feedstuff, rich in cellulose, lignin, and insoluble dietary fibre. Three experimental supplemental diets were formulated: a finely ground, low fibre and nutrient dense diet served as control (CON). For the 2 high fibre diets, 15% heat-treated starch in CON was exchanged with OH, either finely (OH-f) or coarsely ground (OH-c). Litters of 10 primi- and multiparous sows (mean litter size 14.6 ± 0.84) were used. Within a litter, experimental diets were allotted to triplets of 4 piglets. From approximately 12 d of age, piglets’ individual feed intakes were recorded 2 times per day when separated from their dam for 70 min. Piglets could suckle with their dam for the remainder of the day. On d 24 and 25, from the total pool of 120 piglets, seven healthy well-eating piglets per treatment were selected for post-mortem evaluation, resulting in 14 replicates per treatment. Consumption of OH-c and OH-f did not impede clinical health and production performance of piglets. The full stomach weights tended to be greater for OH-c compared to OH-f whereas CON was intermediate (P = 0.083). Supplementing OH significantly increased ileal villus height and caecal dry matter concentration (P < 0.05). For the colon, OH increased its length, contents weight, short-chain fatty acid concentration and reduced total bacterial count as well as γ-proteobacteria count and proportion (P < 0.05). The OH-c treatment specifically increased full gastrointestinal tract weight and caecum contents weight compared to piglets fed CON and OH-f. Furthermore, OH-c reduced colonic crypt depth when compared to OH-f (P = 0.018). In conclusion, supplementing OH to a diet for suckling piglets exerted subtle developmental effects on gastrointestinal morphology and colonic microbial community. These effects were largely independent from the particle size of the OH.}, journal={ANIMAL NUTRITION}, author={Hees, Hubert M. J. and Chiers, Koen and Hartog, Leo A. den and Kempen, Theo A. T. G. van and Maes, Dominiek and Millet, Sam and Janssens, Geert P. J.}, year={2023}, month={Mar}, pages={284–296} }
 @article{kempen_murphy_2022, title={Delineating the extra-nutritional properties of nutrients: characterisation with amino acids}, volume={8}, ISSN={["1836-5787"]}, url={https://doi.org/10.1071/AN22235}, DOI={10.1071/AN22235}, abstractNote={Animal Production Science (continuing Australian Journal of Experimental Agriculture) publishes original research into applied agriculture including animal production, animal-plant interactions, pasture and fodder crops, field crops, extension and horticulture}, journal={ANIMAL PRODUCTION SCIENCE}, author={Kempen, Theo A. T. G. and Murphy, Michael R.}, editor={Bryden, WayneEditor}, year={2022}, month={Aug} }
 @article{kempen_benitez punal_huijser_de smet_2022, title={Tocopherol more bioavailable than tocopheryl-acetate as a source of vitamin E for broilers}, volume={17}, ISSN={["1932-6203"]}, url={https://doi.org/10.1371/journal.pone.0268894}, DOI={10.1371/journal.pone.0268894}, abstractNote={Vitamin E is typically supplied in the form of tocopheryl-acetate (T-Ac) since tocopherol (T) has stability issues. Tocopheryl-acetate, however, must be hydrolyzed in the intestines before it can be absorbed, a step that is purportedly rate-limiting for its bioavailability. The objective of this study was to compare the efficiency of absorption of T-Ac and T in broilers. In addition, two test procedures were evaluated in which animals received the test substances for either 2 or 4 days only. Animals were adapted to diets without supplemental vitamin E (feedstuffs contributed 14±1 ppm natural vitamin E (RRR-tocopherol)) till the age of 25 d (individual housing) or 28 d (group housing). Subsequently, they were fed T-Ac at 80, 53, 36, 24, or 16 ppm or T at 80, 40, 20, 10, or 5 ppm for a period of 4 d (4-di) or 2 d (2-dg), after which serum and liver were collected for analysis of vitamin E. Measured feed vitamin E levels were used for the data analysis; the recovery of T-Ac was 85%, and that of T was 39%. Both test procedures (2 or 4 days) yielded good quality data. Based on linear regression analysis, the relative efficiency with which T-Ac raised tissue levels as compared to T was 0.24 (2-dg) to 0.37 (4-di), with liver and serum yielding similar results. Analysis using more complex dose response models imply that the hydrolysis of T-Ac was strongly dose-dependent and that it could be saturated at doses above approximately 50 ppm in animals only briefly fed T-Ac; for T there was no evidence of saturation. These data imply that T, provided that stable forms can be developed, has the potential to be much more efficient at providing vitamin E to the animal, and on top, can yield much higher tissue levels, than T-Ac.}, number={5}, journal={PLOS ONE}, author={Kempen, Theo A. T. G. and Benitez Punal, Samuel and Huijser, Jet and De Smet, Stefaan}, editor={Tomaszewska, EwaEditor}, year={2022} }
 @article{hees_maes_millet_hartog_kempen_janssens_2021, title={Fibre supplementation to pre-weaning piglet diets did not improve the resilience towards a post-weaning enterotoxigenic E. coli challenge}, volume={105}, ISSN={["1439-0396"]}, DOI={10.1111/jpn.13475}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF ANIMAL PHYSIOLOGY AND ANIMAL NUTRITION}, author={Hees, Hubert and Maes, Dominiek and Millet, Sam and Hartog, Leo and Kempen, Theo and Janssens, Geert}, year={2021}, month={Mar}, pages={260–271} }
 @article{kempen_deixler_2021, title={SARS-CoV-2: influence of phosphate and magnesium, moderated by vitamin D, on energy (ATP) metabolism and on severity of COVID-19}, volume={320}, ISSN={["1522-1555"]}, url={https://doi.org/10.1152/ajpendo.00474.2020}, DOI={10.1152/ajpendo.00474.2020}, abstractNote={ The use of vitamin D to reduce the severity of COVID-19 complications is receiving considerable attention, backed by encouraging data. Its purported mode of action is as an immune modulator. Vitamin D, however, also affects the metabolism of phosphate and Mg, which may well play a critical role in SARS-CoV-2 pathogenesis. SARS-CoV-2 may induce a cytokine storm that drains ATP whose regeneration requires phosphate and Mg. These minerals, however, are often deficient in conditions that predispose people to severe COVID-19, including older age (especially males), diabetes, obesity, and usage of diuretics. Symptoms observed in severe COVID-19 also fit well with those seen in classical hypophosphatemia and hypomagnesemia, such as thrombocytopenia, coagulopathy, dysfunction of liver and kidneys, neurologic disturbances, immunodeficiency, failure of heart and lungs, delayed weaning from a respirator, cardiac arrhythmia, seizures, and, finally, multiorgan failure. Deficiencies of phosphate and Mg can be amplified by kidney problems commonly observed in patients with COVID-19 resulting in their wastage into urine. Available data show that phosphate and Mg are deficient in COVID-19, with phosphate showing a remarkable correlation with its severity. In one experiment, patients with COVID-19 were supplemented with a cocktail of vitamin D3, Mg, and vitamin B12, with very encouraging results. We, thus, argue that patients with COVID-19 should be monitored and treated for phosphate and Mg deficiencies, ideally already in the early phases of infection. Supplementation of phosphate and Mg combined with vitamin D could also be implemented as a preventative strategy in populations at risk. }, number={1}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM}, publisher={American Physiological Society}, author={Kempen, Theo A. T. G. and Deixler, Elisabeth}, year={2021}, month={Jan}, pages={E2–E6} }
 @article{erp_vries_kempen_den hartog_gerrits_2020, title={Circadian misalignment imposed by nocturnal feeding tends to increase fat deposition in pigs}, volume={123}, ISSN={["1475-2662"]}, DOI={10.1017/S0007114519003052}, abstractNote={Abstract}, number={5}, journal={BRITISH JOURNAL OF NUTRITION}, author={Erp, Rik J. J. and Vries, Sonja and Kempen, Theo A. T. G. and Den Hartog, Leo A. and Gerrits, Walter J. J.}, year={2020}, month={Mar}, pages={529–536} }
 @article{van hees_davids_maes_millet_possemiers_hartog_kempen_janssens_2019, title={Dietary fibre enrichment of supplemental feed modulates the development of the intestinal tract in suckling piglets}, volume={10}, ISSN={["2049-1891"]}, DOI={10.1186/s40104-019-0386-x}, abstractNote={Abstract}, number={1}, journal={JOURNAL OF ANIMAL SCIENCE AND BIOTECHNOLOGY}, author={Van Hees, H. M. J. and Davids, M. and Maes, D. and Millet, S. and Possemiers, S. and Hartog, L. A. and Kempen, T. A. T. G. and Janssens, G. P. J.}, year={2019}, month={Oct} }
 @article{santos_awati_hil_kempen_tersteeg-zijderveld_koolmees_smits_fink-gremmels_2019, title={Effects of a feed additive blend on broilers challenged with heat stress}, volume={48}, ISSN={["1465-3338"]}, DOI={10.1080/03079457.2019.1648750}, abstractNote={ABSTRACT We evaluated a blend of medium-chain fatty acids (MCFA), organic acids, and a polyphenol antioxidant on gut integrity. Eighty Ross Broilers were exposed to 20–22°C (control – normothermic) or to 35–39.5°C (heat stress) for eight hours a day for a period of 1 or 5 days. Birds were fed a standard diet, or a diet supplemented with the test blend. Thereafter, birds were euthanized, and intestinal sections were excised for morphological, morphometric and gene expression analyses. Blood samples were collected for glucose-6-phosphate dehydrogenase (G6PD), glutathione peroxidase (GSH-Px) activity and trolox equivalent antioxidant capacity (TEAC) determination. Heart and liver tissues were used to quantify the expression of heat shock proteins 60 and 70 (HSP60 and HSP70, respectively) and inhibitor of kappa light chain gene enhancer in B cells alpha (IKBA). The jejunum was the most sensitive intestinal section, where heat stress modulated the expression of HSP70, of the inflammatory markers IKBA, interleukin 8 (IL-8), interferon gamma (IFNγ), and toll-like receptor 4 (TLR4). Moreover, expression of tight junctions (CLDN1, ZO1 and ZO2) and nutrient transporters (PEPT1 and EAAT3) was modulated especially in the jejunum. In conclusion, the feed additive blend protected intestines during heat stress from the decrease in villus height and crypt depth, and from the increase in villus width. Especially in the jejunum, heat stress played an important role by modulating oxidative stress and inflammation, impairing gut integrity and nutrient transport, and such deleterious effects were alleviated by the feed additive blend. RESEARCH HIGHLIGHTS Jejunum is the most sensitive intestinal segment during heat stress. Heat stress affects the expression of tight junctions and nutrient transporters. Feed management helps to alleviate the disturbances caused by heat stress. A blend of MCFA, organic acids and a polyphenol protects broilers under heat stress.}, number={6}, journal={AVIAN PATHOLOGY}, author={Santos, Regiane R. and Awati, Ajay and Hil, Petra J. and Kempen, Theo A. T. G. and Tersteeg-Zijderveld, Monique H. G. and Koolmees, Peter A. and Smits, Coen and Fink-Gremmels, Johanna}, year={2019}, month={Nov}, pages={582–601} }
 @article{yanez_woyengo_jha_kempen_zijlstra_2019, title={Nutrient digestibility of soybean products in grower-finisher pigs}, volume={97}, ISSN={["1525-3163"]}, DOI={10.1093/jas/skz290}, abstractNote={Abstract}, number={11}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Yanez, Jorge L. and Woyengo, Tofuko A. and Jha, Rajesh and Kempen, Theo A. T. G. and Zijlstra, Ruurd T.}, year={2019}, month={Nov}, pages={4598–4607} }
 @article{erp_vries_van kempen_gerrits_2019, title={Pigs Ferment Enzymatically Digestible Starch when it Is Substituted for Resistant Starch}, volume={149}, ISBN={1541-6100}, DOI={10.1093/jn/nxz072}, abstractNote={ABSTRACT Background Feeding behavior is controlled by satiety mechanisms, which are affected by the extent of starch digestion, and thus resistant starch (RS) intake. Alterations in feeding behavior to changes in RS intake may depend on the adaptation of processes involved when shifting from starch digestion to fermentation or vice versa. Objectives The aim of this study was to investigate how growing pigs adapt their feeding behavior in response to increasing and decreasing dietary RS concentrations. Methods Thirty-six groups of 6 pigs (25.4 ± 2.8 kg; Hypor Libra × Hypor Maxter; male:female, 1:1) were fed diets containing 50% high-amylose maize starch (high RS; HRS) or waxy maize starch (low RS; LRS). Over 28 d, diets were exchanged following a 5-step titration (25% per step) that was executed in the upward (LH) or downward direction (HL). Twelve groups received a control diet to correct for changes over time. Individual feeding behavior and total tract starch digestion and fermentation were evaluated. The response in each parameter to increasing dietary HRS inclusion was estimated through the use of linear regression procedures, and tested for titration direction and sex effects. Results Complete substitution of LRS with HRS increased the proportion of starch fermented, which was greater in LH pigs than in HL pigs (17.6% compared with 8.18%; P < 0.001), and decreased the feed intake (106 g/d; P = 0.021) and meal size (12.6 g; P < 0.001) of LH pigs, but not of HL pigs. In LH pigs, the size of the starch fermentation response positively correlated with the size of the feed intake response (r = 0.90, P < 0.001). Conclusions The attenuated response in starch fermentation in HL pigs indicates that pigs adapt more slowly to dietary supply of digestible starch than to RS, consequently resulting in fermentation of enzymatically digestible starch. Feed intake and feeding behavior only changed in pigs poorly adapting to RS, indicating that adequacy of adaptation, rather than RS itself, drives feed intake. These findings stress the importance of diet history for nutrient digestion and feeding behavior.}, number={8}, journal={JOURNAL OF NUTRITION}, author={Erp, Rik J. J. and Vries, Sonja and van Kempen, Theo A. T. G. and Gerrits, Walter J. J.}, year={2019}, month={Aug}, pages={1346–1353} }
 @article{langendijk_fleuren_hees_kempen_2018, title={The Course of Parturition Affects Piglet Condition at Birth and Survival and Growth through the Nursery Phase}, volume={8}, ISSN={["2076-2615"]}, DOI={10.3390/ani8050060}, abstractNote={Simple Summary In this study, data were collected on the condition in which piglets were born, and this was related to their position in the birth order, and to the progress of parturition. The objective of the study was to find out if these observations were related to performance in early life, up to 10 weeks. It appeared that the later the piglets were born in a litter, the higher the risk of being stillborn, and this was aggravated in sows that took a relatively long time to give birth to their litter. In the first few piglets in a litter, risk of stillbirth was only 2%, whereas this increased to 17% in piglets born 13th in the litter or later. Similarly, birth order affected the condition of the liveborn piglets, with blood values such as pH being evident of suboptimal oxygenation in piglets born later. These blood values were predictive of neonatal behaviour such as colostrum intake, but also for neonatal survival and growth during suckling and even to 10 weeks of life. These data are the first in piglets to emphasise the impact of condition at birth on survival and growth until the end of the nursery phase. Abstract The aim of this study was to relate the course of parturition to the condition of piglets at birth, based on umbilical cord blood acid-base values, and relate the condition at birth to neonatal survival and performance up to 10 weeks of life. Data were collected from 37 spontaneous unassisted parturitions, and neonatal performance was based on observations of 516 piglets. Stillbirth rate increased from 2% in the first piglets, to 17% in piglets born 13th in the litter or later. This was aggravated in sows with longer than average stage II of parturition. Umbilical cord blood values also reflected the effect of birth order, with pH decreasing and lactate increasing in the course of parturition. Interestingly, sows that had a long expulsion stage of parturition also took longer to give birth to the first four piglets (r = 0.74), suggesting that sows with complicated parturition were already experiencing problems at the start of expulsion of piglets. Piglets with signs of asphyxia, based on umbilical blood lactate higher than 4.46 mmol/L, were slower to start suckling, had a higher risk of neonatal mortality, and had a slower growth rate over the first 10 weeks of life.}, number={5}, journal={ANIMALS}, author={Langendijk, Pieter and Fleuren, Marleen and Hees, Hubert and Kempen, Theo}, year={2018}, month={May} }
 @article{kempen_reijersen_bruijn_de smet_michiels_traber_lauridsen_2016, title={Vitamin E plasma kinetics in swine show low bioavailability and short half-life of all-rac-alpha-tocopheryl acetate}, volume={94}, ISSN={["1525-3163"]}, DOI={10.2527/jas.2016-0640}, abstractNote={Vitamin E is important for animal production because of its effects on health and product quality, but the amount and form required remains controversial. Our objective was to quantify the absolute bioavailability of oral -α-tocopheryl acetate (α-TAc) in swine (22 ± 1 kg and 8 wk old, fitted with jugular catheters) adapted to a diet supplemented with 75 mg/kg -α-TAc; 75 mg/kg was chosen because this level represents the nonweighted average inclusion level in piglet diets across Western key swine-producing countries. For this, a 350-g test meal (6% fat) was supplied at time 0 containing 75 mg deuterated (D9) -α-TAc to 9 animals, and 8 animals received an intravenous () dose containing deuterated (D6) RRR-α-tocopherol (α-T) at one-eighth the oral dose and a test meal without supplemental vitamin E. Plasma samples (12 to 13 per animal) were obtained at incremental intervals over 75 h for analysis of deuterated α-T using liquid chromatography-tandem mass spectrometry. Surprisingly, the i.v. dose rapidly disappeared from plasma and then reappeared. The half-life for this first peak was only 1.7 ± 0.3 min. The second peak had an appearance rate (Ka) of 0.10 ± 0.06 d and a half-life of 5.9 ± 1.2 h. Oral dosing resulted, after a lag of 56 min, in a Ka of 0.91 ± 0.21 d and a half-life of 2.6 ± 0.8 h. The bioavailability for oral α-TAc was 12.5%, whereas the area under the curve was only 5.4%. This low bioavailability, small area under the curve, and short half-life are likely because of various factors, that is, the use of only 6% fat in the diet, the use of the acetate ester and , and the high dose relative to requirements. In conclusion, i.v. dosed vitamin E shows both a rapid and a very slow pool, whereas orally dosed vitamin E shows a single slow pool. The oral material has a very short half-live (44% of i.v. or 2.6 h), low bioavailability (12.5%), and a very small area under the curve (5.4%), bringing into question the efficacy of typical doses of vitamin E in swine diets for alleviating oxidative stress.}, number={10}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Kempen, T. A. T. G. and Reijersen, M. H. and Bruijn, C. and De Smet, S. and Michiels, J. and Traber, M. G. and Lauridsen, C.}, year={2016}, month={Oct}, pages={4188–4195} }
 @article{fouhse_gaenzle_regmi_kempen_zijlstra_2015, title={High Amy lose Starch with Low In Vitro Digestibility Stimulates Hindgut Fermentation and Has a Bifidogenic Effect in Weaned Pigs(1-3)}, volume={145}, ISSN={["1541-6100"]}, DOI={10.3945/jn.115.214353}, abstractNote={BACKGROUND
Dietary amylose resists enzymatic digestion, thereby providing a substrate for microbial fermentation that stimulates proliferation of beneficial microbiota and production of short-chain fatty acids (SCFAs) in the large intestine of pigs and humans. However, the effect of increasing dietary amylose in pigs immediately postweaning on growth, nutrient digestibility and flow, and intestinal microbial and SCFA profiles has not been studied and can be used as a model for newly weaned human infants.


OBJECTIVE
We studied the effects of increasing dietary amylose on growth, nutrient digestibility, and intestinal microbial and metabolite profiles in weaned pigs.


METHODS
Weaned pigs (n = 32) were randomly allocated to 1 of 4 diets containing 67% starch with 0%, 20%, 28%, or 63% amylose for 21 d. Subsequently, pigs were killed to collect feces and digesta for measuring starch digestion and microbial and metabolite profiles.


RESULTS
Feeding weaned pigs 63% compared with 0%, 20%, and 28% amylose decreased (P < 0.05) feed intake by 5% and growth by ≥ 12%. Ileal digestibility of dry matter decreased (P < 0.05) by 10% and starch by 9%, thereby increasing (P < 0.05) hindgut fermentation, cecal and colonic total SCFAs, and colonic Bacteroides, and lowering (P < 0.01) ileal, cecal, and colonic pH in pigs consuming 63% compared with 0%, 20%, and 28% amylose. Cecal and colonic Bifidobacteria spp. increased by 14-30% (P < 0.05) and Clostridium clusters IV and XIVa were decreased (P < 0.01) in pigs consuming 63% compared with 0%, 20%, and 28% amylose.


CONCLUSION
Increasing dietary amylose in pigs immediately postweaning stimulated hindgut fermentation and Bifidobacteria spp., thereby manipulating the gut environment, but also reduced intake and growth. An optimum dietary amylose concentration should be determined, which would maintain desired growth rate and gut environment in weaned pigs.}, number={11}, journal={JOURNAL OF NUTRITION}, author={Fouhse, Janelle M. and Gaenzle, Michael G. and Regmi, Prajwal R. and Kempen, Theo A. T. G. and Zijlstra, Ruurd T.}, year={2015}, month={Nov}, pages={2464–2470} }
 @article{cools_maes_decaluwe_buyse_kempen_liesegang_janssens_2014, title={Ad libitum feeding during the peripartal period affects body condition, reproduction results and metabolism of sows}, volume={145}, ISSN={["1873-2232"]}, DOI={10.1016/j.anireprosci.2014.01.008}, abstractNote={To overcome negative energy balance during the peripartal period of sows, an ad libitum feeding strategy (ADLIB) as alternative for commonly used restricted feeding (STANDARD, on average 3kg feed/day) was evaluated. Plasma metabolites and thyroid hormones, change of back fat thickness (BF), reproductive traits, and piglet performance were monitored. Voluntary feed intake of ADLIB sows declined at farrowing but was still more than twice the amount of what was offered to STANDARD sows. Consequently, ADLIB sows lost less BF than STANDARD sows (P=0.041). Additionally, BF change was affected by body condition. LEAN sows (BF<18mm on d 105 of gestation) lost less BF than MODERATE sows (18mm≤BF≤22mm) which lost less BF than FAT sows (BF>22mm) (P<0.001). Except for a decreased percentage of stillborn piglets for MODERATE sows (P=0.044), reproduction results were not affected. Piglet weaning weight of ADLIB-FAT and STANDARD-MODERATE sows was reduced in comparison with that of ADLIB-LEAN sows (P=0.005). Regardless of body condition, all metabolites and thyroid hormones measured showed a time dependent profile (P<0.001). On d 112 of gestation increased concentrations of creatinine (P=0.004), non-esterified fatty acids (P=0.039), and serum crosslaps (P=0.016) for STANDARD sows were observed. Triglycerides were increased for FAT sows (P<0.001), and decreased faster over time for ADLIB (P=0.013) and for FAT (P=0.012). Although ad libitum feeding during the peripartal period only resulted in less mobilization of muscle, fat, and bone reserves on d 112 of gestation, results of BF change and piglet weaning weight indicated that ad libitum feeding is beneficial for sow performance provided that BF is below 22mm.}, number={3-4}, journal={ANIMAL REPRODUCTION SCIENCE}, author={Cools, A. and Maes, D. and Decaluwe, R. and Buyse, J. and Kempen, T. A. T. G. and Liesegang, A. and Janssens, G. P. J.}, year={2014}, month={Mar}, pages={130–140} }
 @article{koger_o'brien_burnette_kai_kempen_heugten_kempen_2014, title={Manure belts for harvesting urine and feces separately and improving air quality in swine facilities}, volume={162}, ISSN={["1878-0490"]}, DOI={10.1016/j.livsci.2014.01.013}, abstractNote={Modern swine facilities have not been designed to maximize manure value nor to minimize NH3 emission. These benefits can possibly be achieved by harvesting urine and feces separately using a conveyor belt placed at a 4° angle beneath the slats. Urine drains from this belt into a gutter leading to a closed storage vessel while feces remain on the belt for up to 24 h. Such a belt was evaluated in a partially slatted swine facility housing 80–100 grower pigs in five separate experiments. Fecal DM was determined as a function of both belt residence time and collection time-of-day. The driest feces were obtained with daily collections at 0600 h. Collections at this time of day resulted in a 9.8±5.0% increase in DM over collection at 1500 h (P=0.07). Under steady state conditions, feces were collected at 49±5% DM and output was 0.26±0.05 kg DM pig−1 d−1 suggesting an apparent feed DM digestibility of 82.8±2.1%. Urine collected was 1.3±0.2 L pig−1 d−1, equivalent to 33±6% of the water intake. Emissions from this facility were for ammonia 1.03±0.20 kg pig−1 yr−1 or 5.9±1.0% of the intake N and for methane 1.05±0.29 kg pig−1 yr−1 or 0.64±0.18% of the feed energy. Odor emission at the ventilation fan was 1.9 OU animal−1 s−1. All three emission parameters were substantially less than literature values for conventional houses. In conclusion, the belt system was easy to operate and allowed for the separate collection of urine and feces resulting in reduced odor nuisance. Technically, it resulted in feces that could be harvested at 49% DM, and emissions of only 1 kg NH3 and CH4 pig−1 yr−1.}, journal={LIVESTOCK SCIENCE}, author={Koger, J. B. and O'Brien, B. K. and Burnette, R. P. and Kai, R. and Kempen, M. H. J. G. and Heugten, E. and Kempen, T. A. T. G.}, year={2014}, month={Apr}, pages={214–222} }
 @misc{van kempen_deixler_crook_2013, title={Hypophosphatemia as a key factor in sudden infant death syndrome (SIDS)?}, volume={118}, ISSN={["0300-9734"]}, DOI={10.3109/03009734.2013.781252}, abstractNote={Dear Sir, 
 
Sudden Infant Death Syndrome or SIDS remains an important cause of mortality in infants. The 2011 publication of Siren and Siren (1) and the subsequent letter to the editor (2) focus on critical diaphragm failure as a possible cause and provide plausible evidence. However, these articles do not explore the metabolic basis for this critical diaphragm failure. Several authors, including Aubier et al. (3) and Fiaccadori et al. (4) have described that the diaphragm is extremely susceptible to hypophosphatemia, and this may be the origin of the symptoms reported by Siren and Siren. Hence, it may well be the yet unexplored underlying mechanism responsible for SIDS. 
 
A reason for suspecting hypophosphatemia as the cause for SIDS is because neonates are extremely prone to developing hypophosphatemia as shown in numerous publications (e.g. (5-8)). A very brief period of stress, like separation from the mother or a brief period of illness, can result in phosphaturia severe enough to result in the loss of 50% of the free phosphate pool within 24 hours. This results in an immediate drop in blood phosphate levels. Worse, this hypophosphatemia can subsequently become aggravated over the course of 1–2 weeks without obvious visible symptoms and despite resumption of normal eating behavior, something not reported in older subjects. In infants with risk factors for SIDS like intrauterine growth retardation, exposure to cigarette smoke, male sex, and heat stress, this phosphaturetic stress response is enhanced possibly through augmented or longer-lasting sympathetic activity (9,10), and, hence, they are more prone to develop severe hypophosphatemia and ATP deficiency. 
 
Hypophosphatemia not only affects contraction of the diaphragm, but it is also involved in the formation of 2,3-diphosphoglycerate (2,3-DPG; more correctly referred to as 2,3-bisphosphoglycerate) in erythrocytes. This 2,3-DPG regulates the release of oxygen from hemoglobin. Tissues with a high metabolic activity result in high levels of 2,3-DPG in the blood causing the liberation of oxygen (11-13). Hypophosphatemia impedes the formation of 2,3-DPG, which subsequently prevents the release of oxygen from hemoglobin and, in effect, suffocates the tissue. Thus, severe hypophosphatemia results in signs of asphyxiation despite adequate access to free air (14), either through inducing an ATP deficiency affecting the diaphragm or through inhibiting oxygen release from hemoglobin. For example, in briefly stressed subjects, in parallel with the drop in plasma phosphate, a doubling of the ratio of pCO2/pO2, an increase in SpO2, and lactic acidosis were observed but without obvious visible signs of distress. If severe enough, this could lead to death from inner suffocation (SIDS). The presence of fetal hemoglobin may also play a role in SIDS. Fetal hemoglobin purportedly has a higher binding affinity for oxygen (15) and thus could predispose an infant to SIDS when 2,3-DPG is compromised. 
 
Other symptoms of SIDS can also be explained by hypophosphatemia. Hypophosphatemia can lead to petechiae: minor hemorrhages caused by platelet dysfunction (16,17) and often seen postmortem in SIDS victims. Similarly, pulmonary edema (18) has been linked to hypophosphatemia, as have cardiac arrhythmias (19,20). Hypophosphatemia is also implicated in the morbidity and mortality associated with refeeding syndrome (21) and in hypophosphatemic rickets, which is more prevalent in boys (22) in line with a higher incidence of SIDS in boys. 
 
Siren and Siren's (1) comment that REM sleep inhibits intercostal muscles compounded by diurnal rhythms in blood phosphate could explain why SIDS strikes during night-time REM sleep. Also, phosphate has a seasonal rhythm with lows in the winter which could explain a higher prevalence of SIDS in this season, and 2,3-DPG is lower in infants exposed to cigarette smoke which could explain a higher incidence of SIDS in houses of smokers (23,24). 
 
In summary, both the etiology as well as the symptoms of SIDS can be explained by hypophosphatemia. A brief stressor can induce hypophosphatemia in infants, particularly in those with SIDS risk factors, and aggravate it despite resumption of normal food intake. This since the urinary loss of phosphate induced by stress or a large drop in metabolic rate and the subsequent enhanced phosphate demand for re-started anabolic processes cannot be quickly compensated by normal dietary intake. This hypophosphatemia can aggravate to the point of affecting O2 release from red blood cells through a depletion of 2,3-DPG or affect diaphragm contractility through ATP deficiency, either one which leads to death from apparent suffocation: SIDS.}, number={2}, journal={UPSALA JOURNAL OF MEDICAL SCIENCES}, author={Van Kempen, Theo A. T. G. and Deixler, Elisabeth and Crook, Martin A.}, year={2013}, month={May}, pages={143–144} }
 @article{cools_maes_decaluwe_buyse_kempen_janssens_2013, title={Peripartum changes in orexigenic and anorexigenic hormones in relation to back fat thickness and feeding strategy of sows}, volume={45}, ISSN={["1879-0054"]}, DOI={10.1016/j.domaniend.2013.04.003}, abstractNote={Highly prolific sows often experience peripartum hypophagia, resulting in decreased production rate. Leptin, ghrelin, and resistin are known as feed intake-regulating hormones in many species, but it is yet unknown how feeding strategy and body condition will affect these hormones around parturition in sows. In the present study, a total of 63 sows, parity 2 to 7 were divided over 2 treatment groups which were fed either restricted (RESTRICT) or ad libitum (ADLIB) during the peripartum period (day 106 of gestation until day 7 of lactation). Within each treatment group, sows were assigned to 1 of 3 body condition groups based on back fat thickness at day 106 of gestation: <18 mm (LEAN), between 18 and 22 mm (MODERATE), and >22 mm (FAT). Postprandial blood samples were taken on days 107, 109, and 112 of gestation and on days 1, 3, and 5 of lactation. With RIA, leptin, ghrelin, and resistin of each sample were analyzed. For both leptin and resistin, the hormonal profile gradually increased throughout the peripartum period (P < 0.001), whereas ghrelin peaked on day 109 of gestation compared with day 107 of gestation and day 1 of lactation. Other time points were intermediate between those two (P < 0.001). The peripartum profile of leptin was significantly higher for FAT sows than for the 2 other condition groups. No effect of body condition on ghrelin and resistin concentrations was observed. None of the 3 measured hormones were affected by feeding strategy. In conclusion, during the peripartum period feed intake of sows did not affect leptin, ghrelin, or resistin profiles. Leptin was the only hormone investigated that reflected body condition. Although body condition and late gestation feed intake have been previously described as risk factors for peripartum hypophagia, they did not induce hypophagia in any of the sows or affect the profile of the observed feed intake-regulating hormones during the peripartum period.}, number={1}, journal={DOMESTIC ANIMAL ENDOCRINOLOGY}, author={Cools, A. and Maes, D. and Decaluwe, R. and Buyse, J. and Kempen, T. A. and Janssens, G. P.}, year={2013}, month={Jul}, pages={22–27} }
 @article{meer_gerrits_bosch_holst_moreto_buurman_kulik_kempen_2012, title={Chenodeoxycholic acid reduces intestinal permeability in newly weaned piglets}, volume={90}, ISSN={["1525-3163"]}, DOI={10.2527/jas.50998}, abstractNote={Piglets are highly susceptible to gut health-related problems. Intravenously administered chenodeoxycholic acid (CDCA) affects gut health mediated through glucagon-like peptide 2 (GLP-2). To test whether CDCA is a suitable feed additive for improving gut health, a trial was performed with newly weaned (21 d) piglets offered a diet with or without 60 mg CDCA/kg feed (n = 24/treatment). Upon weaning, piglets were fasted for 16 h and then intragastrically dosed with 20 g test feed in 40 g water. Subsequently, a jugular blood sample was taken on 45, 90, 135, or 180 min for analysis of GLP-2, peptide YY (PYY), and glucose. Afterwards, piglets were offered the experimental diets ad libitum. On days 3.5, 7.5, and 10.5 after weaning, serum responses to an intragastric dose of lactulose and Co-EDTA were tested at 2 h after dosing in 8 piglets per treatment. Immediately thereafter, piglets were euthanized, intestines were harvested, and permeability was measured ex vivo using the everted gut sac technique with 4 kDa fluorescein isothiocyanato (FITC)-dextran as marker at 25, 50, and 75% of the length of the small intestine. Dietary CDCA did not affect (P > 0.05) ADFI, ADG, G:F, blood glucose, and plasma GLP-2 and PYY. Serum cobalt and lactulose at day 10.5 tended to be lower in CDCA pigs compared with control pigs. Serum cobalt and lactulose concentrations were positively correlated (r = 0.67; P < 0.01). In conclusion, CDCA tended to reduce intestinal permeability at 10.5 d after weaning when fed to newly weaned piglets, implying that CDCA deserves further study as a means for improving intestinal health. The positive correlation found between Co-EDTA and lactulose indicates that both marker molecules measure similar change in permeability.}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Meer, Y. and Gerrits, W. J. J. and Bosch, M. and Holst, J. J. and Moreto, M. and Buurman, W. A. and Kulik, W. and Kempen, T. A. T. G.}, year={2012}, month={Dec}, pages={302–304} }
 @article{woodward_regmi_gaenzle_kempen_zijlstra_2012, title={Slowly digestible starch influences mRNA abundance of glucose and short-chain fatty acid transporters in the porcine distal intestinal tract}, volume={90}, ISSN={["1525-3163"]}, DOI={10.2527/jas.53877}, abstractNote={The relationship between starch chemistry and intestinal nutrient transporters is not well characterized. We hypothesized that inclusion of slowly instead of rapidly digestible starch in pig diets will decrease glucose and increase short-chain fatty acid (SCFA) transporter expression in the distal gut. Weaned barrows (n = 32) were fed 4 diets containing 70% starch [ranging from 0 to 63% amylose and from 1.06 (rapidly) to 0.22%/min (slowly) rate of in vitro digestion] at 3 × maintenance energy requirement in a complete randomized block design. Ileal and colon mucosa was collected on day 21 to quantify mRNA abundance of Na(+)-dependent glucose transporter 1 (SGLT1), monocarboxylic acid transporter 1 (MCT1), and Na(+)-coupled monocarboxylate transporter (SMCT). Messenger RNA was extracted and cDNA manufactured prior to relative quantitative reverse transcription PCR. Data were analyzed using the 2(-Δ ΔC)(T) method, with β-actin and glyceraldehyde-3-phosphate dehydrogenase as reference genes, and regression analysis was performed. As in vitro rate of digestion decreased, SGLT1 linearly increased (P < 0.05) in the ileum. Contrary to SGLT1, MCT1 tended to linearly decrease (P = 0.08) in the ileum and increased quadratically (P < 0.001) in the colon with decreasing rate of digestion. Starch digestion rate did not affect SMCT in the ileum; however, colonic SMCT quadratically decreased (P < 0.01) with decreasing rate of digestion. In conclusion, in contrast to our hypothesis, slowly digestible starch increased ileal glucose and decreased ileal SCFA transporter mRNA abundance, possibly due to an increased glucose in the luminal ileum. Effects of starch on colonic SCFA transporter mRNA abundance were inconsistent.}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Woodward, A. D. and Regmi, P. R. and Gaenzle, M. G. and Kempen, T. A. T. G. and Zijlstra, R. T.}, year={2012}, month={Dec}, pages={80–82} }
 @article{zijlstra_jha_woodward_fouhse_kempen_2012, title={Starch and fiber properties affect their kinetics of digestion and thereby digestive physiology in pigs}, volume={90}, ISSN={["1525-3163"]}, DOI={10.2527/jas.53718}, abstractNote={Traditionally in swine nutrition, analyses of starch and fiber have focused on assessing quantity; however, both have a wide range of functional properties making them underappreciated nutrients. Starch ranging from low to high amylose changes from rapidly digestible in the upper gut to poorly digestible but fermentable in the lower gut thereby changing from a source of glucose to VFA source. Likewise, fibers ranging from low to high viscosity affect digesta flow and from slowly to rapidly fermentable alter production of VFA serving as energy for the gut or whole body. Our hypothesis is that total extent, kinetics, and site of digestion or fermentation of starch and fiber are important for whole body nutrient use and intestinal health. To elucidate their effects, we developed in vitro, lab-based methodologies to describe kinetics of digestion and fermentation and linked these with in vivo models including i) ileum cannulation to collect digesta, ii) portal-vein catheterization to sequentially sample blood, iii) slaughter method to collect site-specific intestinal tissue and digesta, and iv) indirect calorimetry. Using these methods, kinetics of nutrient absorption was associated with pancreatic and intestinal hormones released into the portal vein, intestinal microbiota, and gene expression in intestinal tissue and microbiota. These studies confirmed that slowly digestible starch is partially degraded in the distal small and large intestine and fermented into VFA including butyrate (10-fold increase in net portal appearance), which reduces insulin responses by 60% and whole body energy use. Starch entering the distal intestine altered mRNA abundance of nutrient transporters and was bifidogenic. Extremely viscous purified fiber dampened glycemic responses and reduced digesta passage rate by 50% thereby increasing ileal digestion of dietary nutrients whereas increased fiber in feed grains reduced nutrient digestibility. Fermentable fiber increased butyrate and insulin production. These methods will therefore support elucidation of mechanisms that link starch and fiber properties to whole body nutrient use and intestinal health.}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Zijlstra, R. T. and Jha, R. and Woodward, A. D. and Fouhse, J. and Kempen, T. A. T. G.}, year={2012}, month={Dec}, pages={49–58} }
 @article{wijtten_verstijnen_kempen_perdok_gort_verstegen_2011, title={Lactulose as a marker of intestinal barrier function in pigs after weaning}, volume={89}, ISSN={["1525-3163"]}, DOI={10.2527/jas.2010-3571}, abstractNote={Intestinal barrier function in pigs after weaning is almost exclusively determined in terminal experiments with Ussing chambers. Alternatively, the recovery in urine of orally administered lactulose can be used to assess intestinal permeability in living animals. This experiment was designed to study the barrier function of the small intestine of pigs over time after weaning. The aim was to relate paracellular barrier function (measured by lactulose recovery in the urine) with macromolecular transport [measured by horseradish peroxidase (HRP) using Ussing chambers] and bacterial translocation to assess whether lactulose recovery is related to possible causes of infection and disease. Forty gonadectomized male pigs (6.7 ± 0.6 kg) were weaned (d 0) at a mean age of 19 d, fitted with urine collection bags, and individually housed. Pigs were dosed by oral gavage with a marker solution containing lactulose (disaccharide) and the monosaccharides l-rhamnose, 3-O-methylglucose, and d-xylose at 2 h and at 4, 8, and 12 d after weaning. The recovery of sugars in the urine was determined over 18 h after each oral gavage. The day after each permeability test, the intestines of 10 pigs were dissected to determine bacterial translocation to the mesenteric lymph nodes and jejunal permeability for HRP in Ussing chambers. Recovery of l-rhamnose in urine was affected by feed intake and by the time after weaning (P ≤ 0.05). Recovery of lactulose from the urine was greater (P ≤ 0.05) at 4, 8, and 12 d after weaning compared with the first day after weaning and was negatively correlated with feed intake (r = -0.63, P ≤ 0.001). The mean translocation of aerobic bacteria to the mesenteric lymph nodes was greater at 5 and 13 d after weaning compared with d 1 (P ≤ 0.05). Lactulose recovery showed no correlation with permeability for HRP nor with bacterial translocation (P > 0.05). Although both lactulose recovery and bacterial translocation increased over time after weaning, lactulose recovery did not correlate with the permeability for HRP nor bacterial translocation within a pig (P > 0.05). Therefore, we conclude that lactulose recovery in the urine of pigs after weaning is not associated with risk factors for infections. However, it appears to be possible to measure paracellular barrier function with orally administered lactulose in pigs shortly after weaning. Further studies will reveal whether this variable is relevant for the long-term performance or health of pigs after weaning.}, number={5}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Wijtten, P. J. A. and Verstijnen, J. J. and Kempen, T. A. T. G. and Perdok, H. B. and Gort, G. and Verstegen, M. W. A.}, year={2011}, month={May}, pages={1347–1357} }
 @article{regmi_metzler-zebeli_gaenzle_kempen_zijlstra_2011, title={Starch with High Amylose Content and Low In Vitro Digestibility Increases Intestinal Nutrient Flow and Microbial Fermentation and Selectively Promotes Bifidobacteria in Pigs}, volume={141}, ISSN={["1541-6100"]}, DOI={10.3945/jn.111.140509}, abstractNote={Diets containing different starch types can affect enzymatic digestion of starch and thereby starch availability for microbial fermentation in the gut. However, the role of starch chemistry in nutrient digestion and flow and microbial profile has been poorly explained. Eight ileal-cannulated pigs (29.4 ± 0.9 kg body weight) were fed 4 diets containing 70% purified starch (amylose content, <5, 20, 28, and 63%; reflected by in vitro maximal digestion rate; 1.06, 0.73, 0.38, and 0.22%/min, respectively) in a replicated 4 × 4 Latin square. Ileal and fecal starch output, postileal crude protein yield, fecal total SCFA and total butyrate content, and gene copies of Bifidobacterium spp. in feces were higher (P < 0.05) when pigs consumed the slowly digestible starch diet than the remaining 3 starch diets. The in vitro starch digestion rate had a negative, nonlinear relationship with ileal starch flow (R(2) = 0.98; P < 0.001). Ileal starch flow was positively related to Bifidobacterium spp. (R(2) = 0.27; P < 0.01), Lactobacillus group (R(2) = 0.22; P < 0.01), and total butyrate content (R(2) = 0.46; P < 0.01) but was not related to Enterobacteriaceae (R(2) < 0.00; P = 0.92). In conclusion, starch with high amylose content and low in vitro digestibility increased postileal nutrient flow and microbial fermentation and selectively promoted Bifidobacterium spp. in the distal gut.}, number={7}, journal={JOURNAL OF NUTRITION}, author={Regmi, Prajwal R. and Metzler-Zebeli, Barbara U. and Gaenzle, Michael G. and Kempen, Theo A. T. G. and Zijlstra, Ruurd T.}, year={2011}, month={Jul}, pages={1273–1280} }
 @article{regmi_kempen_matte_zijlstra_2011, title={Starch with High Amylose and Low in Vitro Digestibility Increases Short-Chain Fatty Acid Absorption, Reduces Peak Insulin Secretion, and Modulates Incretin Secretion in Pigs}, volume={141}, ISSN={["1541-6100"]}, DOI={10.3945/jn.110.132449}, abstractNote={Diets containing different starch types affect peripheral glucose and insulin responses. However, the role of starch chemistry in kinetics of nutrient absorption and insulin and incretin secretion is poorly understood. Four portal vein-catheterized pigs (35.0 ± 0.2 kg body weight) consumed 4 diets containing 70% purified starch [0-63.2% amylose content and 0.22 (slowly) to 1.06%/min (rapidly) maximum rate of in vitro digestion] for 7-d periods in a 4 × 4 Latin square. On d 7, blood was collected for 12 h postprandial with simultaneous blood flow measurement for determining the net portal appearance (NPA) of nutrients and hormones. The NPA of glucose, insulin, C-peptide, and glucose-dependent insulinotropic polypeptide (GIP) during 0-4 h postprandial were lower (P < 0.05) and those of butyrate and total SCFA were higher (P < 0.05) when pigs consumed the diet containing slowly digestible compared with rapidly digestible starch. The peak NPA of insulin occurred prior to that of glucose when pigs consumed diets containing rapidly digestible starch. The kinetics of insulin secretion had a linear positive relation with kinetics of NPA of glucose (R(2) = 0.50; P < 0.01). In conclusion, starch with high amylose and low in vitro digestibility decreases the kinetics of glucose absorption and insulin and GIP secretion and increases SCFA absorption and glucagon-like peptide-1 secretion. In conclusion, starch with high amylose content and a lower rate and extent of in vitro digestion decreased glucose absorption and insulin secretion and increased SCFA absorption.}, number={3}, journal={JOURNAL OF NUTRITION}, author={Regmi, Prajwal R. and Kempen, Theo A. T. G. and Matte, J. Jacques and Zijlstra, Ruurd T.}, year={2011}, month={Mar}, pages={398–405} }
 @article{kempen_regmi_matte_zijlstra_2010, title={In Vitro Starch Digestion Kinetics, Corrected for Estimated Gastric Emptying, Predict Portal Glucose Appearance in Pigs}, volume={140}, ISSN={["1541-6100"]}, DOI={10.3945/jn.109.120584}, abstractNote={In vitro starch digestion is used for predicting the in vivo glucose response, but their relationship has not been defined thoroughly. To clarify, in vitro starch digestion using a modified Englyst-assay was compared to portal glucose appearance in pigs. Four portal vein-catheterized pigs (43.2 +/- 4.8 kg body weight) were fed 4 diets containing 70% purified starch ranging from slowly to rapidly digestible [maximal rate of in vitro digestion (%)/min: 0.22 (slowly), 0.38, 0.73, and 1.06 (rapidly)] for 7-d periods in a 4 x 4 Latin square. In vivo (R2 = 0.964) and in vitro (R2 = 0.998) data were modeled using a Chapman-Richards model that accurately described the sigmoidal glucose-release profiles. Across samples, the extent of glucose recovered was less in vivo than in vitro (69 vs. 42% of starch). The rate of glucose release adjusted for plateau effects was lower in vivo (0.35 vs. 0.89%/min), whereas the shape parameter adjusted for plateau effects (sigmoidal modifier) was higher in vivo (37.9 vs. 13.7). Consequently, peak glucose release in vivo occurred 69 min postprandial, whereas it occurred only 6 min into the second stage of digestion in vitro. Cumulative portal glucose appearance was strongly related (R2 = 0.89; P < 0.001) to in vitro glucose release, although a nonlinear bias was observed. After correcting in vitro release with predicted gastric emptying, the relationship improved and became linear (R2 = 0.95; P < 0.001). In conclusion, in vitro starch digestion kinetics predict portal glucose appearance up to 8 h postprandial accurately provided that in vitro data are corrected for gastric emptying.}, number={7}, journal={JOURNAL OF NUTRITION}, author={Kempen, Theo A. T. G. and Regmi, Prajwal R. and Matte, J. Jacques and Zijlstra, Ruurd T.}, year={2010}, month={Jul}, pages={1227–1233} }
 @article{sola-oriol_kempen_torrallardona_2010, title={Relationships between glycaemic index and digesta passage of cereal-based diets in pigs}, volume={134}, ISSN={["1878-0490"]}, DOI={10.1016/j.livsci.2010.06.091}, abstractNote={Changes in the rate of passage of digesta may affect feed digestibility and glycaemia, but at the same time glycaemia may also regulate stomach emptying and as a consequence digesta passage rate. The correlations between the glycaemic index (GI) of 12 cereals, the ileal and total tract, dry matter (DM) and organic matter (OM) digestibilities and the ileal digesta flow characteristics of pig feeds containing them were studied. GI for each cereal was calculated as the maximal glucose release rate per minute using an in vitro digestibility system. Pigs fitted with an ileal T-cannula were used to measure the DM and OM digestibilities (ileal and total tract) of the corresponding cereal-based diets, and their ileal digesta flow rate, lag time to initial flow of digesta (Tlag) and mean retention time (MRT). Titanium dioxide (TiO2) was used as indigestible marker. The Spearman's correlations between the GI, the parameters of digesta flow and the digestibility values were estimated. GI was significantly correlated with ileal digestibility of OM (r = 0.58; P < 0.05), ileal digesta flow rate (r = 0.79; P < 0.01), Tlag (r = − 0.76; P < 0.01) and MRT (r = − 0.87; P < 0.01). DM and OM ileal digestibility and the digesta flow parameters were also correlated (P < 0.05). Positive significant correlations between cereal GI, feed digestibility and digesta flow rate have been found.}, number={1-3}, journal={LIVESTOCK SCIENCE}, author={Sola-Oriol, D. and Kempen, T. and Torrallardona, D.}, year={2010}, month={Sep}, pages={41–43} }
 @article{regmi_matte_kempen_zijlstra_2010, title={Starch chemistry affects kinetics of glucose absorption and insulin response in swine}, volume={134}, ISSN={["1878-0490"]}, DOI={10.1016/j.livsci.2010.06.092}, abstractNote={Starch chemistry may affect kinetics of nutrient absorption and insulin secretion. The objective was to define the glucose absorption kinetics and insulin response in swine to diets containing starch with a wide range in chemistry and in vitro digestion patterns. Diets tested contained purified starch (700 g/kg diet) ranging from rapid to slow digestible starch [maximal rate of in vitro glucose release (%)/min: 1.53, rapid; 0.94, moderate rapid; 0.37, moderate slow; and 0.14, slow]. In vitro rate of starch digestion was characterized using an assay modified after Englyst et al. (2003). In vivo kinetics were determined using four pigs (35.0 ± 0.2 kg) surgically fitted with catheters in the portal vein and carotid artery and a portal blood flow probe. Pigs were fed for 7-d periods in a 4 × 4 Latin square. On d 7, blood was collected for 12 h postprandially. Net glucose absorption differed (P < 0.05) among diets at 45, 90, 120, and 150 min postprandial. Cumulative glucose absorption up to 12 h did not differ among rapid, moderate rapid, and moderate slow digestible starch diets, but these diets had a higher (P < 0.05) cumulative glucose absorption than slow digestible starch diets. In addition, portal plasma insulin and C-peptide release peaked at 30 min postprandial and differed (P < 0.05) among diets at 30 and 60 min postprandial, except between moderate rapid and moderate slow digestible starch diets. In conclusion, starches with a wide difference in in vitro starch digestion affect kinetics of glucose absorption and insulin response in swine.}, number={1-3}, journal={LIVESTOCK SCIENCE}, author={Regmi, P. R. and Matte, J. J. and Kempen, T. A. T. G. and Zijlstra, R. T.}, year={2010}, month={Sep}, pages={44–46} }
 @article{muley_heugten_moeser_rausch_kempen_2007, title={Nutritional value for swine of extruded corn and corn fractions obtained after dry milling}, volume={85}, ISSN={["1525-3163"]}, DOI={10.2527/jas.2006-127}, abstractNote={The experiment was designed to assess whether corn fractions or extrusion of corn can result in feed ingredients with a greater nutritional value than corn. Corn grain (8.0% CP, 0.21% P, 9.8% NDF) was processed by extrusion (82.8 degrees C, 345 kPa steam pressure for 12 s) or by dry milling to derive fractions rich in germ (13.1% CP, 1.19% P, 17.2% NDF), hulls (8.1% CP, 0.27% P, 32.6% NDF), and endosperm, namely tails (6.6% CP, 0.07% P, 3.6% NDF) and throughs (7.4% CP, 0.15% P, 4.5% NDF). Relative recovery in each fraction was 16, 20, 44, and 20%, respectively. Ileal digestibility of DM, P, and amino acids was determined using diets containing 7.0% CP from soybean meal and 5.3% CP from one of the test products. To allow for determination of standardized ingredient, ileal digestibility, basal endogenous AA losses were determined using a protein-free diet (74.6% cornstarch and 18.7% sucrose). Soybean meal ileal digestibility was determined using a diet (12.3% CP) based on soybean meal (23.3%). Eight barrows (27 +/- 2 kg) fitted with T-cannulas were fed 8 experimental diets (5-d adaptation and 2-d collection period) such that each diet was evaluated in at least 5 barrows. Relative to corn (77.9 +/- 1.2%), ileal digestibility of DM was greater for extruded corn (82.5%; P = 0.02), tails (85.9%; P < 0.01), and throughs (85.0%; P < 0.01), but it was lower for hulls (62.2%; P < 0.01) and germ (51.1%; P < 0.01). For P, corn (41.6 +/- 9.5%), throughs (47.2%), and hulls (57.3%) had similar ileal digestibility, but germ (7.9%) had lower ileal digestibility (P = 0.02) than corn; tails (27.6%) and extruded corn (23.5%) were not different from corn or germ but were lower than throughs and hulls. For total AA, corn (84.7 +/- 2.4%), throughs (84.3%), and hulls (85.8%) had similar ileal digestibility, but germ (76.6%) had lower ileal digestibility (P < 0.01) than corn; tails (82.0%) and extruded corn (81.7%) were intermediate. In conclusion, germ and hulls have a low ileal DM digestibility; germ also has low AA and P digestibility. Extrusion improved the ileal DM digestibility of corn. To maximize the ileal digestibility, removal of germ and hull from corn or extrusion of corn may thus be of interest.}, number={7}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Muley, N. S. and Heugten, E. and Moeser, A. J. and Rausch, K. D. and Kempen, T. A. T. G.}, year={2007}, month={Jul}, pages={1695–1701} }
 @article{kai_kaspers_kempen_2006, title={Modeling sources of gaseous emissions in a pig house with recharge pit}, volume={49}, DOI={10.13031/2013.22040}, abstractNote={Ammonia, methane, and odor from a fully slatted pig housing facility equipped with a pit-recharge manure system were modeled with a view to quantify the sources of ammonia, methane, and odor. Emissions of ammonia, methane, and odor were measured during three weeks in two environmental chambers containing ten pigs. The chambers had fully slatted floors, and the pit was precharged with 120 L of water. After one week, the pigs were removed from the chambers, while measurements of emissions were continued for an additional two weeks. The trial was conducted in duplicate with pigs weighing 25 and 45 kg, respectively. Ammonia and methane were modeled to estimate concentrations in the presence (sigmoidal model) and upon removal of pigs (single pool exponential decay model). The combined model accounted for 89% of the variation in ammonia. The pit contributed 50% to 60% of the ammonia emission, while the slats contributed the remaining 40% to 50%. The mean ammonia emissions with pigs present were 26 and 17 g AU-1 d-1 with pigs weighing 25 and 45 kg, respectively. The model explained 98% of the observed variation in methane concentrations. The pigs and freshly excreted feces were the principal sources of methane, while the recharge pit did not emit significant amounts of methane. With pigs in the chambers, the mean methane emissions amounted to 14 g AU-1 d-1 irrespective of weight. Geometric mean odor emissions with pigs present were 6.0 OU AU-1 s-1 (95% confidence interval 4.2-8.6 OU AU-1 s-1). Odor emissions were unaffected by the presence of pigs (p > 0.10). This indicates that manure, whether in the pit or on contaminated slats, is the main source of odor in pig houses, whereas the pigs themselves are of minor importance.}, number={5}, journal={Transactions of the ASABE}, author={Kai, P. and Kaspers, B. and Kempen, Theo}, year={2006}, pages={1479–1485} }
 @article{kempen_heugten_moeser_muley_sewalt_2006, title={Selecting soybean meal characteristics preferred for swine nutrition}, volume={84}, ISSN={["1525-3163"]}, DOI={10.2527/2006.8461387x}, abstractNote={As environmental constraints become more important issues for the animal industry, selecting feed ingredients that yield good animal performance but also minimize environmental impact of animal production becomes critical. The objective of this research was to identify which compositional features would be desirable for soybean meal to maximize nutritional value and minimize animal waste. Eight soybean samples were selected from a database of 72, such that maximal variability for CP, NDF, and ADF content was obtained. Samples were subsequently processed into meal using standardized procedures. In Experiment 1, 8 cannulated pigs were used to determine ileal digestibility following a Latin square design. In Experiment 2, 5 of the samples were used in complete feeds and 10 pigs were used in a crossover Latin square design to determine the total tract digestibility, odorants in fresh and 5-d-old manure, and ammonia emission from manure. Differences up to 6% in ileal DM digestibility and 8% in ileal CP digestibility were observed. This difference was reduced to 1.1% for total tract DM digestibility and 4% for total tract CP digestibility. Differences in odorant concentration were 3-fold and for in vitro ammonia emission were 42%. The only compositional variable with a significant effect on digestibility was stachyose, which negatively affected ileal digestibility of DM (r = -0.80, P = 0.02) and energy (r = -0.73, P = 0.04). None of the compositional variables measured affected ileal CP digestibility. Ileal CP digestibility, however, was correlated with estimated CP fermentation in the large intestine (r = -0.86, P = 0.06) and with in vitro ammonia emission after 48 h (r = -0.81, P = 0.09). In conclusion, nutritionally relevant variability exists in soy varieties. Low stachyose content is important for maximizing ileal energy digestibility of soybean meal. Although no compositional variable was identified that explained differences in ileal CP digestibility, maximizing ileal CP digestibility is of interest for maximizing the nutritional value of soybean meal and possibly for reducing ammonia and odor emissions.}, number={6}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Kempen, T. A. T. G. and Heugten, E. and Moeser, A. J. and Muley, N. S. and Sewalt, V. J. H.}, year={2006}, month={Jun}, pages={1387–1395} }
 @article{qiao_gumpertz_van kempen_2005, title={Stability of a pancreatic enzyme cocktail during in vitro protein digestibility assays}, volume={29}, ISSN={["0145-8884"]}, DOI={10.1111/j.1745-4514.2005.00003.x}, abstractNote={To maximize the efficiency of utilization of a pancreatic enzyme cocktail and estimate the contamination for in vitro protein digestibility assays, the specific activity losses of trypsin and chymotrypsin and the digestion of the enzyme proteins were studied. In the absence of protein substrate, increase of enzyme concentration augmented the half-lives of trypsin and chymotrypsin and decreased the digestion of enzymatic proteins. In contrast, in the presence of substrate, increase of enzyme concentration decreased trypsin's half-life. Increase of pH augmented the digestion of enzymatic proteins. The results indicated the optimum time for utilization of the enzymes depended on pH, enzyme concentration and presence of substrate. At the time when digestion of the proteins ceased, the average size of the hydroly sates was calculated between 3.1 and 5.4 amino acid residues, suggesting most proteins in the enzyme cocktail would be detected as digestible proteins.}, number={2}, journal={JOURNAL OF FOOD BIOCHEMISTRY}, author={Qiao, YR and Gumpertz, M and Van Kempen, T}, year={2005}, month={Apr}, pages={205–220} }
 @article{narushin_kempen_wineland_christensen_2004, title={Comparing infrared spectroscopy and egg size measurements for predicting eggshell quality}, volume={87}, ISSN={["1537-5129"]}, DOI={10.1016/j.biosystemseng.2003.12.006}, abstractNote={The objective of the undertaken research was to compare infrared spectroscopy (IRS) and egg size measurements for non-destructive evaluation of eggshell strength. For the infrared analysis of the eggs from broiler breeds Ross 508×Ross and Case×Ross, an infrared spectrometer equipped with an upward looking diffuse reflection accessory was used. Data were collected from 5000 to 640 cm−1 at a resolution of 2 cm−1. Infrared and egg size parameters were correlated with eggshell quality parameters obtained using invasive techniques. Shell thickness was best predicted by IRS (correlation coefficient 0·52 versus 0·32 based on size measurements). Shell fracture force, maximal deformation, and shell stiffness were predicted with comparable accuracy by both IRS and egg size parameters (correlation coefficients ranging from 0·24 to 0·42). IRS was also able to predict shell weight with reasonable accuracy (correlation coefficient 0·72). Data suggest that neither physical size measurements or IRS yield high-quality predictions of eggshell quality, but IRS, given its speed and ability to predict multiple parameters with one measurement appears the favourable technique to explore further.}, number={3}, journal={BIOSYSTEMS ENGINEERING}, author={Narushin, VG and Kempen, TA and Wineland, MJ and Christensen, VL}, year={2004}, month={Mar}, pages={367–373} }
 @article{kim_ferket_powers_stein_kempen_2004, title={Effects of different dietary acidifier sources of calcium and phosphorus on ammonia, methane and odorant emission from growing-finishing pigs}, volume={17}, ISSN={["1976-5517"]}, DOI={10.5713/ajas.2004.1131}, abstractNote={The objective of this study was to investigate the effects of different sources of Ca and P on urine and ileal digesta pH, and ammonia (NH3), methane (CH4), and odor emission. In experiment 1, eight pigs (commercial three-way cross; initial BW 67±3 kg) were arranged in a repeated 4×4 Latin Square design. All pigs were equipped with a T-cannula in the distal ileum. Four corn-soybean meal based diets were formulated. Diet 1 was the control in which dicalcium phosphate (DCP) and limestone (CaCO3) were used as the sources of inorganic P and Ca. In Diets 2 and 3, H3PO4, monocalcium phosphate (MCP), and CaSO4 replaced DCP and CaCO3 as the inorganic sources of P and Ca. Diet 4 was similar to Diet 1 except that it was fortified with HCl to provide an acid load similar to that of diet 2. Urine and ileal digesta pH were determined in pigs fed each of these diets. In Exp. 1, urine pH decreased (p<0.05) in animals consuming diets containing H3PO4-CaSO4 (5.85±0.38) and MCP-CaSO4 (5.73±0.30) compared with the DCP-CaCO3 diet (6.89±0.24). In the pigs consuming H3PO4-CaSO4, ileal digesta pH decreased compared with the control (5.52±0.28 vs. 6.66±0.17; p<0.05). Based on the results of Exp. 1, a total of four trials were performed in environmental chambers for determining how NH3, CH4, and odor were affected by the different dietary Ca and P sources (Exp. 2). In Exp. 2, pigs fed the H3PO4-CaSO4 diet had decreased (30%) NH3 emissions compared with the control (p<0.05). Also, a combination of MCP-CaCO3-CaCl2 decreased NH3 emission by 15% (p<0.05). Emission of CH4 was decreased only with the H3PO4-CaSO4 diet with 14% (p<0.05). Odorant emission of phenolics and volatile fatty acids increased roughly three-fold with the DCP-CaSO4 diet but was not affected by other test diets. In conclusion, acidogenic Ca and P sources in swine diets can decrease the urinary pH and reduce NH3 and CH4 emission from swine facilities. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 8 : 1131-1138)}, number={8}, journal={ASIAN-AUSTRALASIAN JOURNAL OF ANIMAL SCIENCES}, author={Kim, IB and Ferket, PR and Powers, WJ and Stein, HH and Kempen, TATG}, year={2004}, month={Aug}, pages={1131–1138} }
 @article{van kempen_peak_yanrui_2004, title={In vitro digestibility could meet quality control needs}, volume={76}, ISBN={0014-9624}, number={8}, journal={Feedstuffs}, author={Van Kempen, T. and Peak, S. and YanRui, Qiao}, year={2004}, pages={11} }
 @article{qiao_lin_odle_whittaker_van kempen_2004, title={Refining in vitro digestibility assays: Fractionation of digestible and indigestible peptides}, volume={82}, ISSN={0021-8812 1525-3163}, url={http://dx.doi.org/10.2527/2004.8261669x}, DOI={10.2527/2004.8261669x}, abstractNote={Typically, in vitro methods used for estimating the amount of ileal digestible AA do not exhaustively digest samples, and arbitrary methods for separating digestible from indigestible protein are used. This may lead to over- or underestimation of digestibility coefficients. A method that exhaustively digests proteins using pepsin and pancreatin was developed, and the first objective of this research was to confirm that exhaustive digestion was indeed appropriate and to determine the fractionation method for separating digestible from indigestible proteins. For this, three homoarginine-labeled animal proteins were prepared. Samples were subsequently digested in vivo and in vitro to determine which fraction should be considered indigestible, and in vitro followed by in vivo to determine whether the extent of digestion in vivo was improved by predigestion. In vivo, soluble but unabsorbed peptides were smaller than 1 kDa, suggesting that the size of soluble peptides is not what prevents their absorption. Thus, all in vitro-soluble proteins should be considered digestible. In vitro, 88 +/- 3% of the soluble peptides were smaller than 1 kDa, with the remainder between 1 and 5 kDa, suggesting that in vitro digestion is less complete. Predigested samples were digested in vivo to the same size distribution as the nonpredigested samples. The second objective was to test whether in vitro digestibility assays based on these principles equaled in vivo digestibility. For this, digestibility data for 25 animal proteins were compared. Results showed a lack of correlation between lysine digestibility coefficients; however, across samples, the extent of digestion did not differ for lysine (P = 0.71), threonine (P = 0.26), methionine (P = 0.18), or valine (P = 0.66), whereas in vitro digestibility coefficients were lower for (the less water-soluble) histidine (P = 0.05), isoleucine (P < 0.01), leucine (P < 0.01), and phenylalanine (P = 0.05). In conclusion, in vitro digestibility assays should exhaustively digest proteins to mimic in vivo digestibility. All in vitro-soluble peptides could be considered digestible, because in vivo, no large soluble peptides were observed whose size prevented them from being absorbed. However, an in vitro assay based on these principles lacked precision for highly water-soluble AA, and underestimated digestibility for other AA. Better solubilization of the digesta and more replicates may improve the in vitro assay further.}, number={6}, journal={Journal of Animal Science}, publisher={Oxford University Press (OUP)}, author={Qiao, Y. and Lin, X. and Odle, J. and Whittaker, A. and van Kempen, T. A. T. G.}, year={2004}, month={Jun}, pages={1669–1677} }
 @article{qiao_kempen_2004, title={Technical note: Comparison of Raman, mid, and near infrared spectroscopy for predicting the amino acid content in animal meals}, volume={82}, DOI={10.2527/2004.8292596x}, abstractNote={The objective of this study was to compare three infrared spectroscopy techniques for routine evaluation of AA in animal meals. Animal meals (n = 54) with known AA contents were scanned with a near (NIRS), mid (FTIR), and Raman infrared spectrometer. For NIRS and Raman, samples were scanned "as is", whereas for FTIR, samples had to be finely ground before scanning to obtain reasonable spectra. Both FTIR and Raman data suffered from noise; for Raman, this prevented the development of calibrations. Using derivatized spectral data and a standardized outlier removal procedure, calibrations for nutritionally relevant AA could be developed that were equivalent for both NIRS and FTIR. The variation across AA tested explained (r2) by these calibrations was 70% for NIRS and 68 + 3% for FTIR. Removing spectral data between 4,000 and 2,000 cm(-1) from the FTIR data improved calibrations (P = 0.09) and explained an average of 77% of the variation with prediction errors lower than obtained with NIRS (P < 0.01). However, FTIR calibrations based on the entire or the shortened spectrum contained fewer samples than did NIRS calibrations (41 and 39 vs. 48, respectively; P < 0.01) because more samples were removed as outliers. In conclusion, Raman did not yield acceptable spectra for animal meals. For FTIR, sample preparation was more time-consuming because the samples required grinding before analysis. Using the entire mid-infrared range, FTIR calibrations were comparable to NIRS calibrations. Calibrations for FTIR were improved by eliminating wave numbers that exhibited more noise, resulting in prediction errors better than those for NIRS. Thus, FTIR has the potential to yield better calibrations for AA in animal meals than NIRS, but it requires greater care in sample preparation and scanning.}, number={9}, journal={Journal of Animal Science}, author={Qiao, Y. and Kempen, Theo}, year={2004}, pages={2596–2600} }
 @article{otto_yokoyama_hengemuehle_bermuth_kempen_trottier_2003, title={Ammonia, volatile fatty acids, phenolics, and odor offensiveness in manure from growing pigs fed diets reduced in protein concentration}, volume={81}, DOI={10.2527/2003.8171754x}, abstractNote={The objective of this study was to investigate whether reducing dietary CP concentration decreases fecal VFA, manure ammonia (NH3) emission and odor, and urinary phenolic metabolites. Six barrows were allotted to one of six dietary treatments in a Latin square design. Treatments consisted of four corn-soybean meal based diets containing 15, 12, 9, and 6% CP, a casein-based diet containing 15% CP, and a protein-free diet (0% protein). Crystalline AA were included in the 12, 9, and 6% CP diets. The casein-based and protein-free diets were used to determine basal endogenous contribution of VFA, phenolics, NH3, and manure odor. Pigs were housed individually in metabolism cages to allow total collection of feces and urine. Feces and urine were collected and pooled within pig and period. Feces and urine were analyzed for VFA and phenolic metabolite concentrations, respectively. Feces and urine were then mixed, stored, and fermented at room temperature for 30 d. For NH3 determination, headspace air was sampled from manure slurries at 24, 48, and 72 h after fermentation. Slurry samples were placed into vials, capped, and randomized before odor panel evaluation. Odor offensiveness was classified on severity: 1 = non-offensive; 2 = mildly offensive; 3 = moderately offensive; 4 = strongly offensive; and 5 = extremely offensive. Reducing dietary CP increased (P < 0.05) fecal VFA concentrations but did not affect phenolic concentrations in urine. Manure NH3 emission was reduced (P < 0.05) as dietary CP concentration decreased from 15 to 0%. The 15% diet had the least offensive manure slurry with odor qualitative ranking of 2.58 (i.e., mild-moderately offensive). Compared with the 15% CP diet, manure from the 9 and 6% CP diets was found to be more offensive (P < 0.05), with qualitative rankings of 2.92 and 3.10, respectively. Odor qualitative rank for the 12% CP, protein-free diet, and casein-based diet did not differ from that of the 15% CP diet. These results indicate that reduction in dietary CP concentrations decreases manure NH3 emission, but it does not diminish manure odor offensiveness and fecal VFA concentrations.}, number={7}, journal={Journal of Animal Science}, author={Otto, E. R. and Yokoyama, M. and Hengemuehle, S. and Bermuth, R. D. Von and Kempen, Theo and Trottier, N. L.}, year={2003}, pages={1754–1763} }
 @article{moeser_see_heugten_morrow_kempen_2003, title={Diet and evaluators affect perception of swine waste odor: An educational demonstration}, volume={81}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2142759654&partnerID=MN8TOARS}, DOI={10.2527/2003.81123211x}, abstractNote={An educational program was developed for extension agents, faculty, and graduate students to illustrate the effect of diet composition on odor from swine manure. Participants in this program first received a 2-h detailed review on odorous compounds in manure and the effect of diet on odor. For the second portion of the training, nine manure samples were used from pigs fed diets formulated with feed ingredients predicted to have different effects on odor emission or a nutritionally adequate corn-soybean meal diet. Participants were instructed to rate the odor from these samples for pleasantness, irritation, and intensity on a scale of 0 (best) to 8 (worst), using manure from the corn-soybean meal fed pig as the reference with a score defined as 4 for each variable. Results obtained were summarized and discussed before concluding the program. Participants were Cooperative Extension Agents (n = 13) with swine responsibilities and graduate students and faculty (n = 8). The manure from the diet with the worst odor scores (1% garlic) was rated at 70% more odorous across the three odor variables (P < 0.05) than the diet with the least odorous manure (purified diet). Even though a reference sample was used, individual participants differed in their perception of irritation across samples (P < 0.05), ranging in average score across diets from 2.4 (moderately better than reference) to 5.0 (slightly worse than reference). With extension agents, a 1 to 7 scale (very interesting to not at all interesting) was used for evaluation of the training session. Participants found the material to be interesting (mean = 1.7, SD = 0.7) and the training exercise to be well organized and coherent in its presentation (mean = 1.8, SD = 0.7). Participants enjoyed this training and learned that differences in odor are achievable through altering diet composition, and that the response to swine odor depends on individual odor perception.}, number={12}, journal={Journal of Animal Science}, author={Moeser, A. J. and See, M. T. and Heugten, Eric and Morrow, W. E. M. and Kempen, Theo}, year={2003}, pages={3211–3215} }
 @article{kempen_baker_heugten_2003, title={Nitrogen losses in metabolism trials}, volume={81}, DOI={10.2527/2003.81102649x}, abstractNote={The utilization of dietary nitrogen has been the subject of much research. For example, NRC (1998) provides a wealth of information on the subject that is based on an extensive review of literature. For a 45-kg pig fed a corn-soybean meal diet, the NRC predicts an efficiency of N utilization of 35%. This low efficiency is the result of approximately 7% of the dietary CP not being digestible and the equivalent of 8% of the dietary CP being lost in endogenous excretions. The synthesis of endogenous material results in the obligatory catabolism of the equivalent of 10% of the dietary N. These losses account for 25% of the dietary N intake. The remaining CP (75% of dietary) is available for lean tissue accretion; however, as a result of mismatches between requirements and dietary supply, approximately 30% is degraded and used for energy production. The remainder is actually used for lean tissue growth, but approximately 10% is not accreted due to inefficiencies in lean tissue growth, and summation of these losses results in N utilization in the neighborhood of 35% (van Kempen and van Heugten, 2000). Feed wastage and poor animal health can deteriorate this efficiency even further. Chung and Baker (1992) demonstrated that with diets formulated to be nearly 100% digestible (which would minimize indigestible and endogenous losses and optimally match the requirement of the animal, thereby minimizing the 30% mismatch), efficiencies of 60% were achievable in nursery pigs, lending credibility to the above calculation.}, number={10}, journal={Journal of Animal Science}, publisher={Oxford University Press (OUP)}, author={Kempen, T. A. T. G. Van and Baker, D. H. and Heugten, Eric}, year={2003}, pages={2649–2650} }
 @article{moeser_kempen_2002, title={Dietary fibre level and enzyme inclusion affect nutrient digestibility and excreta characteristics in grower pigs}, volume={82}, ISSN={["0022-5142"]}, DOI={10.1002/jsfa.1234}, abstractNote={Abstract}, number={14}, journal={JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE}, author={Moeser, AJ and Kempen, TATG}, year={2002}, month={Nov}, pages={1606–1613} }
 @article{heugten_kempen_2002, title={Growth performance, carcass characteristics, nutrient digestibility and fecal odorous compounds in growing-finishing pigs fed diets containing hydrolyzed feather meal}, volume={80}, DOI={10.2527/2002.801171x}, abstractNote={This study was designed to determine the effects of hydrolyzed feather meal inclusion on growth performance, carcass characteristics, nutrient digestibility and fecal odorous compounds in modern lean growth genotype pigs. Two hundred forty pigs (BW = 23.2 +/- 1.3 kg) were allotted based on BW and sex to a 2 x 6 factorial arrangement of treatments (four pens per treatment; five pigs per pen) in a randomized complete block design. Factors consisted of 1) sex (barrows or gilts) and 2) dietary treatment (0, 2, 4, 6, 8, or 10% hydrolyzed feather meal). Diets were formulated to contain 1.00, 0.90, 0.75, or 0.60% apparent ileal digestible lysine for phases 1 to 4, respectively, with other amino acids provided at an ideal ratio. Available P and ME were kept constant within each phase. No significant interactions between feather meal inclusion and sex were observed for growth performance (P > 0.15). Body weight gain was reduced (P < 0.05) for pigs fed 10% feather meal compared to pigs fed 0, 4, or 8% feather meal. Feed intake of pigs fed 10% feather meal was reduced (P < 0.05) compared to pigs fed 0 or 4% feather meal. Ultrasound backfat measurements tended (P = 0.12) to increase with increasing levels of feather meal. Daily lean gain was less (P < 0.05) in pigs fed 10% feather meal than in pigs fed either 0, 2, 4, or 8% feather meal. Digestibility of N measured on wk 9 decreased quadratically (P < 0.001) with increasing levels of feather meal. Phosphorus digestibility increased in a linear fashion (P < 0.02), however, the improvement in P digestibility with increasing levels of feather meal was more pronounced in barrows compared to gilts (interaction, P < 0.05). Fecal samples obtained from pigs fed 0, 4, or 8% feather meal were analyzed for odorous compounds. Concentrations of butanoic, pentanoic, and 3-methylbutanoic acid were greater (P < 0.05) and concentrations of 3-methylphenol, 4-methylphenol, indole, and decane were less (P < 0.05) in feces from pigs fed feather meal. These results suggest that feather meal can be included in diets for growing-finishing pigs at a rate of 8%. Excretion of N in feces increased but P excretion decreased with increasing levels of feather meal. Odorous compounds in feces can be affected by the inclusion of hydrolyzed feather meal, but the exact impact of these changes on odor perception remains to be elucidated.}, number={1}, journal={Journal of Animal Science}, author={Heugten, Eric and Kempen, Theo}, year={2002}, pages={171–178} }
 @article{kempen_mccomas_2002, title={Infrared spectroscopy as a tool for assessing fat quality}, volume={11}, ISSN={["1056-6171"]}, DOI={10.1093/japr/11.2.191}, abstractNote={SUMMARY Feed-grade fats are an important energy source in animal diets. However, their quality can vary greatly, affecting their value. A convenient method for routine quality control of such fats is infrared spectroscopy. By using field samples with known composition, excellent calibrations for free fatty acids and iodine value were obtained, especially using mid-infrared spectroscopy. For moisture, unsaponifiables, and energy, the quality of the calibration was limited by the quality of the reference method; with a better reference method, acceptable calibrations can be developed as well. No acceptable calibration was obtained for oxidative stability as measured with the peroxide method and the active oxygen method. In conclusion, infrared spectroscopy offers a rapid method for limited quality control of fat samples.}, number={2}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Kempen, TA and McComas, S}, year={2002}, pages={191–201} }
 @article{kempen_kim_heugten_2002, title={Pigs as recyclers for nutrients contained in Bermuda grass harvested from spray fields}, volume={81}, ISSN={["0960-8524"]}, DOI={10.1016/S0960-8524(01)00129-8}, abstractNote={The ability of pigs to use nitrogen and energy in Bermuda grass was evaluated in order to assess whether Bermuda grass harvested from spray fields could be fed to pigs as a means to recycle nitrogen. Digestibility of Bermuda grass incorporated into corn-soybean meal diets was evaluated in heavy finishing pigs and gestating sows. Results suggest that Bermuda grass digestibility is negative in animals not adapted to a high-fiber diet. Enzymes improve this digestibility, but even with enzymes, nitrogen digestibility was poor. Pigs fed a diet containing 10% Bermuda grass required a one week adaptation period for maximal digestion; following adaptation, pigs can digest approximately 40% of the energy in Bermuda grass but none of the nitrogen. Feeding Bermuda grass to pigs as a means of recycling nitrogen is thus not recommended.}, number={3}, journal={BIORESOURCE TECHNOLOGY}, publisher={Elsevier BV}, author={Kempen, TATG and Kim, I and Heugten, E}, year={2002}, month={Feb}, pages={233–239} }
 @article{kempen_kim_jansman_verstegen_hancock_lee_gabert_albin_fahey_grieshop_et al._2002, title={Regional and processor variations in the ileal digestible amino acid content of soybean meals measured in growing swine}, volume={80}, DOI={10.2527/2002.802429x}, abstractNote={To assess differences in soybean meal quality related to region of production, researchers in Illinois, Kansas, North Carolina, The Netherlands, and Ohio collected four soybean meal samples processed locally at least 15 d apart. These samples were assayed for ileal amino acid digestibility by pigs using a common soybean meal and a soy protein concentrate as references, and a low-protein casein diet for determination of endogenous amino acid losses. Digestibility was determined at each university using seven barrows surgically fitted with ileal cannulas in a 7 x 7 Latin square design. The experimental diets contained 17% CP from the test material except for the low-protein casein diet. Animals were fed twice daily, 12 h apart, at a level of 45 g x kg(-0.75) BW for each meal. Following a 5-d adaptation period, ileal digesta were collected for two 12-h periods for 2 d to be used for determination of ileal digestibility. Variation in amino acid digestibility was very small among and within sites and was much smaller than variation in the concentration of amino acids. Among sites, samples from The Netherlands had less total and thus digestible lysine and methionine than the U.S. samples (P < 0.05). The soybean meals tested in this experiment were approximately 4% higher in amino acids than that reported in the NRC (1998). True (standardized) digestibilities, however, were very similar to NRC values except for cysteine and threonine, which were 5 and 3 percentage points lower in this experiment, respectively. In conclusion, soybeans grown in the United States and locally processed into soybean meal were very similar in nutritional composition. Soybean meals produced in The Netherlands were lower in lysine and methionine (P < 0.05) but had a digestibility similar to that produced in the United States.}, number={2}, journal={Journal of Animal Science}, author={Kempen, T. A. T. G. Van and Kim, I. B. and Jansman, A. J. M. and Verstegen, M. W. A. and Hancock, J. D. and Lee, D. J. and Gabert, V. M. and Albin, D. M. and Fahey, G. C. and Grieshop, C. M. and et al.}, year={2002}, pages={429–439} }
 @article{kaspers_burnette_koger_van kempen_van kempen_2002, title={Separating urine from feces may be key to flexibility}, volume={74}, ISBN={0014-9624}, number={21}, journal={Feedstuffs}, author={Kaspers, B. and Burnette, P. and Koger, J. and Van Kempen, M. and Van Kempen, T.}, year={2002}, pages={11} }
 @article{qiao_gumpertz_van kempen_2002, title={Stability of pepsin (EC 3.4.23.1) during in vitro protein digestibility assay}, volume={26}, ISSN={["0145-8884"]}, DOI={10.1111/j.1745-4514.2002.tb00759.x}, abstractNote={To maximize the efficiency of utilization of pepsin and estimate the contamination of pepsin for in vitro protein digestibility assays, the specific activity decay and peptide bond hydrolysis of pepsin incubated at different pH and concentration were studied with the bovine hemoglobin method and the o-phthaldialdehyde method, respectively. It was found that increase of pH and concentration of pepsin increased pepsin's half-life for both specific activity decay and peptide bond hydrolysis. The half-life for specific activity decay was not extended by the presence of a substrate protein. The results indicated the time needed to maximize pepsin utilization depended on pH and the concentration of pepsin. At the time when all specific activity of pepsin was lost, the average size of pepsin autolysates was between 6.9 and 12.1 amino acid residues, suggesting most peptic protein would be fractionated as digestible protein.}, number={4}, journal={JOURNAL OF FOOD BIOCHEMISTRY}, author={Qiao, YR and Gumpertz, M and Van Kempen, T}, year={2002}, month={Sep}, pages={355–375} }
 @article{kempen_powers_sutton_2002, title={Technical note: Fourier transform infrared (FTIR) spectroscopy as an optical nose for predicting odor sensation}, volume={80}, DOI={10.2527/2002.8061524x}, abstractNote={Quantifying odor is important for objectively assessing the impact of animal production systems on surrounding areas. A possible method that has received little attention is Fourier transform (mid) infrared spectroscopy (FTIR). Gases that contribute to odor have unique infrared spectra, and the advantage of FTIR over electronic nose technology or gas chromatography is that theoretically all these gases can be analyzed instantaneously. To determine the feasibility of FTIR for predicting odor, 71 air samples analyzed by olfactometry were scanned in a spectrometer using an 84-m path-length gas cell. Scans were obtained over a period of about 1 min and from 4,000 to 740 cm(-1) with a resolution of 0.5 cm(-1). Calibrations for predicting odor were developed using partial least squares regression with full cross-validation. Air samples were obtained from experiments with pigs fed diets formulated to alter odor emission or from stored manure. Odor threshold dilution ratios averaged 676+/-491 units, with a range from 120 to 2,161. Using these samples, a prediction error for odor sensation of 344 units (R2 = 0.51) was obtained. Log transformation of the odor data improved the R2 to 0.61. Based on the olfactometry data, it is estimated that the measurement error of olfactometry is 250 units, which limits the R2 of any method to approximately 0.74. Thus, this calibration is very encouraging. In conclusion, FTIR shows promise as a practical means for objectively assessing swine odor.}, number={6}, journal={Journal of Animal Science}, author={Kempen, T. A. T. G. Van and Powers, W. J. and Sutton, A. L.}, year={2002}, pages={1524–1527} }
 @article{moeser_kim_heugten_kempen_2002, title={The nutritional value of degermed, dehulled corn for pigs and its impact on the gastrointestinal tract and nutrient excretion}, volume={80}, DOI={10.2527/2002.80102629x}, abstractNote={Three experiments were designed to assess the feeding value and potential environmental benefits of feeding degermed, dehulled corn, a low fiber by-product originating from the corn dry milling process, to pigs. Twelve 27-kg (SE = 0.8) barrows were used in Exp. 1 to measure the apparent fecal digestibility of DM, GE and N of degermed, dehulled corn compared with corn grain. Two diets were formulated to contain either 96.4% of degermed, dehulled corn or corn grain plus supplemental vitamins and minerals. Digestibilities of DM, GE, and N were greater in degermed, dehulled corn (96.2, 96.0, and 93.6%, respectively) compared with corn grain (89.0, 89.0, and 78.4%, respectively) (P < 0.01). Overall, a 67 and 29% reduction in DM and N excretion, respectively, was observed. In Exp. 2, eight 70-kg (SE =1.8) barrows were surgically fitted with ileal cannulae and fed the same diets as in Exp. 1, to measure the ileal digestibility of nutrients in degermed, dehulled corn. Ileal digestibility of DM, energy, and N was 13, 15, and 7% greater in degermed, dehulled corn (P < 0.05). Apparent ileal digestibility coefficients of leucine, methionine, and phenylalanine were greater in degermed, dehulled corn compared with corn grain (P < 0.05) while a trend for a lower tryptophan digestibility in degermed, dehulled corn was observed (P = 0.067). In Experiment 3, 96 nursery pigs with an initial average BW of 8.8 kg (SE = 0.08), fed a starter diet formulated with degermed, dehulled corn or corn grain as the major grain source, were used in a 28-d growth performance study. At the end of the study, 24 pigs (1 pig per pen) were sacrificed and gastrointestinal tract measurements were taken. Daily growth rates of pigs were the same between diets (0.64 kg/d). A trend for reduced feed intake (P = 0.073) in pigs fed degermed, dehulled corn led to a 4% improvement in gain to feed (P < 0.05). Feeding degermed, dehulled corn had no effect on gut fill, gastrointestinal tract weight, or liver weight (P > 0.05). Ileal villus lengths and crypt depths were not affected by feeding degermed, dehulled corn although ileal villus widths were greater in pigs fed corn grain. Results from these trials suggest that corn processed to remove poorly digestible fiber fractions provides more digestible nutrients than corn grain. As a result, degermed, dehulled corn reduces fecal and N excretion, thus providing a means to reduce nutrient excretion.}, number={10}, journal={Journal of Animal Science}, author={Moeser, A. J. and Kim, I. B. and Heugten, Eric and Kempen, Theo}, year={2002}, pages={2629–2638} }
 @article{kempen_heugten_trottier_2001, title={Adipic acid increases plasma lysine but does not improve the efficiency of lysine utilization in swine}, volume={79}, DOI={10.2527/2001.7992406x}, abstractNote={Adipic acid, upon catabolism, results in intermediates that bear a structural similarity to lysine degradation products. The objectives of this research were to determine whether adipic acid affects lysine concentrations in plasma and to evaluate whether adipic acid improves the efficiency of lysine utilization in pigs. In Exp. 1, nursery pigs (n = 14) were fed (for a period of 7 d) either a standard nursery diet or the same diet supplemented with 1% adipic acid to assess effects on plasma amino acid concentrations (plasma collected on d 7). In Exp. 2, nursery pigs (n = 56) were fed (for a period of 15 d) either a control diet or the same diet but deficient in either lysine, threonine, or tryptophan with or without supplemental adipic acid to assess the effects of adipic acid on the efficiency of amino acid utilization. The results from Exp. 1 showed that adipic acid increased plasma lysine (by 18%) but not alpha-amino adipic acid, an intermediate in lysine degradation. Experiment 2 demonstrated that adipic acid did not increase the efficiency of utilization of lysine, threonine, or tryptophan. The lack of effects on alpha-amino adipic acid in Exp. 1 and the lack of a positive effect on the efficiency of utilization of lysine, threonine, and tryptophan suggest that adipic acid does not inhibit the mitochondrial uptake of lysine and(or) its degradation in the mitochondrion. It is concluded that feeding adipic acid increases plasma lysine but does not improve the efficiency of lysine utilization.}, number={9}, journal={Journal of Animal Science}, publisher={Oxford University Press (OUP)}, author={Kempen, Theo and Heugten, Eric and Trottier, N. L.}, year={2001}, pages={2406–2411} }
 @article{heo_odle_lin_kempen_han_2001, title={Determination of Carnitine Renal Threshold and Effect of Medium-Chain Triglycerides on Carnitine Profiles in Newborn Pigs}, volume={14}, ISSN={1011-2367 1976-5517}, url={http://dx.doi.org/10.5713/ajas.2001.237}, DOI={10.5713/ajas.2001.237}, number={2}, journal={Asian-Australasian Journal of Animal Sciences}, publisher={Asian Australasian Association of Animal Production Societies}, author={Heo, K. N. and Odle, J. and Lin, X. and Kempen, T. A. T. G. van and Han, In K.}, year={2001}, month={Feb}, pages={237–242} }
 @article{kempen_2001, title={Dietary adipic acid reduces ammonia emission from swine excreta}, volume={79}, DOI={10.2527/2001.7992412x}, abstractNote={Adipic acid is only partially catabolized when it is fed to animals, and a portion of it is excreted in urine. The excreted portion may lower urinary pH and, as a result, ammonia emission. The present study tested this hypothesis. In Exp. 1, nursery pigs (n = 14) were fed (for a period of 7 d) either a standard nursery diet or the same diet supplemented with 1% adipic acid to assess effects on urinary pH (collected on d 5 or 6) and in vitro ammonia emission from the collected urine samples that were mixed with control feces. In Exp. 2, grower pigs housed 10 each in one of two chambers were fed a control diet or the same diet supplemented with 1% adipic acid. Ventilated air was quantified and analyzed for ammonia using Fourier transform infrared spectroscopy to determine the effects of feeding 1% adipic acid on ammonia emission. The results from Exp. 1 showed that adipic acid strongly reduced urinary pH (from 7.7 to 5.5, P < 0.05). In vitro ammonia emission from these urine samples was significantly reduced at all the time points evaluated (1, 3, 18, and 46 h with reductions of 94, 93, 70, and 39%, respectively, P < 0.05). Experiment 2 showed that adipic acid supplementation reduced ammonia emission by 25% (P < 0.05), which corresponded to the predicted reduction in ammonia emission based on the reduction in manure pH observed. In conclusion, feeding adipic acid lowers urinary pH and reduces ammonia emission. The reduction in ammonia emission, though, does not correspond to the reduction in urinary pH but corresponds to the reduction in fecal pH as a result of mixing the urine and feces, in which feces act as a strong buffer.}, number={9}, journal={Journal of Animal Science}, author={Kempen, Theo}, year={2001}, pages={2412–2417} }
 @misc{kempen_2001, title={Infrared technology in animal production}, volume={57}, ISSN={["0043-9339"]}, DOI={10.1079/wps20010004}, abstractNote={Infrared (IR) spectroscopy is based on the principle that the chemical bonds in organic molecules absorb or emit infrared light when their vibrational state changes. In the near IR part of the spectrum, large changes in vibrational state are observed (overtones), while in the mid IR region, primary vibrations are produced. The latter yields sharper, more clearly defined peaks that are better suited for quantitative purposes. Raman spectroscopy, in which the decay of the vibration is observed after strong excitation of the sample, is a variant on mid IR spectroscopy. A major challenge in applying IR spectroscopy to animal production is sample presentation. Transmission is the most powerful method well suited to liquids and gases but is inappropriate for undiluted solids. Although reflection offers an alternative for solids, it is less than ideal for quantitative purposes as the path length is not known. For pastes and opaque liquids, attenuated total reflectance offers good possibilities for the future as it acts like a transmission device but sample application is simple. A novel method is photo-acoustics in which the heating of a sample (as it absorbs the IR light) is measured using a microphone. IR spectroscopy is typically fast and easy to use. In feedmills it allows the quality (e.g. proximate and nutritionally relevant parameters such as metabolisable energy) of feed ingredients and complete feeds to be monitored. In meat processing IR spectroscopy offers the opportunity to assess meat and fat quality, and perhaps even palatability (texture and flavour). New developments in IR spectroscopy will expand its applications further. These include hand-held instruments that may find use in determining digestive disorders among birds in the field, fibreoptics that will allow instantaneous measurements to be made in almost any part of a plant, tunable lasers (with their much stronger signals) that will make IR spectroscopy much more powerful, and imaging IR spectroscopy which may be used to determine the homogeneity of meat (e.g. colour). IR spectroscopy, with its speed, ease of use and versatility, could be about to become one of the most powerful analytical techniques available to the animal production industries. It promises to allow for improved quality control in virtually every aspect of production, from feed manufacture to final product evaluation.}, number={1}, journal={WORLDS POULTRY SCIENCE JOURNAL}, author={Kempen, T}, year={2001}, month={Mar}, pages={29–48} }
 @article{kempen_park_hannon_matzat_2001, title={Precision nutrition: weighing feed ingredients correctly}, volume={81}, ISSN={["0022-5142"]}, DOI={10.1002/jsfa.876}, abstractNote={Abstract}, number={8}, journal={JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE}, author={Kempen, T and Park, B and Hannon, M and Matzat, P}, year={2001}, month={Jun}, pages={726–730} }
 @article{van heugten_van kempen_1999, title={Methods may exist to reduce nutrient excretion}, volume={71}, number={17}, journal={Feedstuffs}, author={Van Heugten, E. and Van Kempen, T.}, year={1999}, pages={12–13} }
 @article{van kempen_park_hannon_matzat_1999, title={Proper weighing key in making a quality feed}, volume={71}, number={53}, journal={Feedstuffs}, author={Van Kempen, T. and Park, B. and Hannon, M. and Matzat, P.}, year={1999}, pages={12–13} }