@article{eisemann_nienaber_huntington_2022, title={Ractopamine and age alter oxygen use and nitrogen metabolism in tissues of beef steers}, volume={100}, ISSN={["1525-3163"]}, DOI={10.1093/jas/skac304}, abstractNote={Abstract}, number={11}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Eisemann, Joan H. and Nienaber, John A. and Huntington, Gerald B.}, year={2022}, month={Nov} }
 @article{caton_engle_crouse_archibeque_nagaraja_huntington_2020, title={Frontiers in ruminant nutrition: An ASAS-CSAS-WSASAS 2020 Symposium overview}, volume={98}, ISSN={["1525-3163"]}, DOI={10.1093/jas/skaa276}, abstractNote={1Department of Animal Sciences, North Dakota State University, NDSU Dept. 7630, Fargo, ND 58108-6050, USA, 2Animal Sciences, Colorado State University, Fort Collins, CO 80523–1171, USA, 3USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA, 4Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, KS, 66506-5802, USA, 5Animal Science, North Carolina State University, Box 7621. Raleigh, NC, 27695-7621, USA}, number={9}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Caton, Joel S. and Engle, Terry and Crouse, Matthew S. and Archibeque, Shawn and Nagaraja, T. G. and Huntington, Gerald}, year={2020}, month={Sep} }
 @article{huntington_eisemann_2020, title={Past, present and future of protein and N metabolism in ruminants}, volume={98}, ISSN={["1525-3163"]}, DOI={10.1093/jas/skaa278.311}, abstractNote={Abstract}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Huntington, Gerald B. and Eisemann, Joan H.}, year={2020}, month={Nov}, pages={169–169} }
 @article{reis_huntington_hopkins_whisnant_paulino_2015, title={Herbage selection, intake and digestibility in grazing beef cattle}, volume={174}, ISSN={["1878-0490"]}, DOI={10.1016/j.livsci.2015.01.020}, abstractNote={The objectives of this study were to measure voluntary herbage intake in kg of dry matter (DM) per day and in proportions of plant species and components (leaf, stem, dead material) of nonlactating Angus cows under grazing conditions and compare DM herbage intakes to intakes of the same cows when they were nursing their calves. Twenty nonlactating Angus cows (50±12 mo of age, 525±55 kg weight) were selected from a larger herd to create 4 groups of 5 cows with average DM intakes that ranged from 11 to 15 kg/d during lactation. The cows were allocated for 28 d as a group on the pasture that contained 5540 kg DM/ha as tall fescue (Festuca arundinacea), bermudagrass (Cynodon dactylon var. Tifton-85), red clover (Trifolium pratense) and other plants. Pasture composition was measured by visual appraisal and manual separation of pasture clippings. Daily allocations provided approximately 2.5 kg DM/100 kg BW. Each cow was individually fed 0.82 kg supplement DM daily that contained 498 mg of the n-alkane dotriacontane (C32) and 448 mg hexatriacontane (C36) during the last 14 d. Fecal grab samples were collected from each cow during the last 5 d. Grazing intake (8.92±1.5 kg DM/d) was calculated for each cow from C32 intake and ratios of tritriacontane (C33):C32 in feces and did not differ (P=0.97) among cow groups. Individual cow intakes during lactation and after weaning, during grazing, were not correlated. Measured sward and calculated intake proportions of tall fescue (0.58 and 0.65), bermudagrass (0.38 and 0.33), and red clover (0.02 and 0.01) indicated cows selected slightly more tall fescue and less bermudagrass and red clover than was on offer. Manual separations of sward and calculated intake proportions of dead material and stem (0.89 and 0.95), green leaf (0.10 and 0.02) and other material (0.01 and 0.04) were similar. N-alkanes provided credible calculations of intake by grazing cows. Intakes of lactating cows did not predict their intake after weaning.}, journal={LIVESTOCK SCIENCE}, author={Reis, S. F. and Huntington, G. and Hopkins, M. and Whisnant, S. and Paulino, P. V. R.}, year={2015}, month={Apr}, pages={39–45} }
 @article{chavez_siciliano_huntington_2014, title={Intake estimation of horses grazing tall fescue (Lolium arundinaceum) or fed tall fescue hay}, volume={92}, ISSN={["1525-3163"]}, DOI={10.2527/jas.2013-7119}, abstractNote={Six mature geldings of light horse breeds (557 ± 37 kg) were randomly assigned to a nontoxic endophyte-infected tall fescue hay (n = 3) or pasture treatment (n = 3) in a crossover design with 14-d periods to estimate DMI with alkane markers and to compare DMI of hay and pasture. When fed pasture, horses were housed in stalls from 0700 to 1300 h daily with access to water and then grazed pasture as a group in a single 0.4 ha pasture from 1300 to 0700 h. When fed hay, horses were maintained individually in stalls and given access to hay ad libitum from 1300 to 0700 h. All horses were individually fed 225 g oats twice daily treated with hexatriacontane (C36; external marker) and fecal samples were collected at 0700 and 1900 h on d 10 to 14. Fecal samples were mixed, dried, subsampled, and analyzed for tritriacontane (C33) and hentriacontane (C31) as internal markers and C36 as the external marker using gas chromatography. Estimated hay DMI using either C33 (1.75 kg/100 kg BW) or C31 (1.74 kg/100 kg BW) as internal alkane marker did not differ (P = 0.55) from measured hay DMI (1.70 kg/100 kg BW). Pasture DMI and DM digestibility (DMD) estimated with C31 (2.24 kg/100 kg BW and 53.1 g/100 g DMI) or with C33 (2.34 kg/100 kg BW and 56.2 g/100 g DMI) was greater (P = 0.05) than hay DMI and DMD (1.74 kg/100 kg BW and 44.5 g/100 g DMI). Intake estimated with C33 or C31 did not differ (P = 0.35) during hay or pasture. In conclusion, alkanes can be used to estimate pasture or hay DMI and DMD, and pasture intake exceeded hay intake when offered ad libitum.}, number={5}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Chavez, S. J. and Siciliano, P. D. and Huntington, G. B.}, year={2014}, month={May}, pages={2304–2308} }
 @article{drewnoski_huntington_poore_2014, title={Reduced supplementation frequency increased insulin-like growth factor 1 in beef steers fed medium quality hay and supplemented with a soybean hull and corn gluten feed blend}, volume={92}, ISSN={["1525-3163"]}, DOI={10.2527/jas.2013-7372}, abstractNote={Reducing supplementation frequency in calf growing programs can reduce labor and equipment operation costs. However, little is understood about the metabolic response of ruminants to large fluctuations in nutrient intake. Eighteen Angus or Angus × Simmental cross steers (287 ± 20 kg and 310 ± 3.6 d of age) were individually fed 1 of 3 dietary treatments using Calan gates. Dietary treatments consisted of ad libitum hay and no supplement (NS), ad libitum hay and 1% BW (as-fed basis) of supplement daily (DS), or ad libitum hay and 2% BW (as-fed basis) of supplement every other day (SA). The supplement was 90% DM and contained (as-fed basis) 47% corn gluten feed, 47% soybean hulls, 2% feed grade limestone, and 4% molasses. Hay intake and ADG was measured over a 52-d period. Steers were then moved to individual tie stalls. Steers were fed at 0800 h and blood samples were collected every hour from 0600 to 1400 h and at 1800, 2200, and 0200 h over a 2-d period. Gains were increased (P < 0.01) by supplementation but did not differ (P = 0.68) due to supplementation frequency. Average daily gain was 0.45, 0.90, and 0.87 kg ·hd(-1)·d(-1) (SEM ± 0.05) for steers NS, DS, and SA, respectively. Across the 2-d supplementation cycle area under the concentration time curve (AUC) for plasma glucose was increased (P < 0.01) by supplementation but did not differ (P = 0.41) due to supplementation frequency. The AUC for plasma insulin was increased by supplementation (P < 0.01) but did not differ (P = 0.67) due to supplementation frequency. Plasma IGF-1 was increased (P = 0.01) by supplementation and was greater (P = 0.04) for steers supplemented SA than DS. Gains of steers supplemented with a soybean hull and corn gluten feed blend on alternate days did not differ from those supplemented daily suggesting the steers were able to efficiently utilize large boluses of nutrients fed every other day. The effect of less frequent supplementation on IGF-1 deserves further examination as this hormone has been shown to increase protein synthesis.}, number={6}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Drewnoski, M. E. and Huntington, G. B. and Poore, M. H.}, year={2014}, month={Jun}, pages={2546–2553} }
 @article{chavez_huntington_2013, title={Intake in cattle of a ground switchgrass and alfalfa hay mixture blended with various levels of sucrose or citric acid}, volume={184}, ISSN={["0377-8401"]}, DOI={10.1016/j.anifeedsci.2013.05.015}, abstractNote={Abstract Palatability of feed affects voluntary intake. The objectives were to evaluate preference by bovine for sweet (sucrose) or sour (citric acid) blended with a mixture of ground switchgrass (42 g crude protein/kg dry matter) and alfalfa hay (176 g crude protein/kg dry matter). Flavors were dissolved in 50 mL deionized water per kg of hay for blending. In Experiment 1, sucrose hay (S100) had 100 g sucrose added per kg hay. Citric acid hay (CA50) had 50 g citric acid added per kg hay. Control hay (CON) had 50 mL deionized water added per kg hay. In Experiment 2, treatments were CON, sucrose added at 25 g per kg hay (S25), S100, 150 g per kg hay (S150). Citric acid added at 25 g per kg hay (CA25), and CA50. Hays were mixed in a horizontal mixer 3 d prior to each experimental period. Twelve beef cattle (initial BW = 283 ± 25 kg) were housed under a roof on expanded metal flooring with access to six feed locations designated I through VI, west to east. Cattle consumed 1 kg/day of supplement (corn, soybean hulls, and trace mineralized salt) that was fed daily, after hay orts were removed and weighed at 0800. Cattle were offered treatment hay equal to 6 g per kg BW at each feed slot and treatments were randomly assigned to two of the six locations at 0830. Cattle were given a 14-d adaptation to CON followed by a 7-d offer of treatments. In Experiment 1, cattle preferred S100 (3.42 ± 0.04 kg/d) over CON (2.8 ± 0.04 kg/d, P}, number={1-4}, journal={ANIMAL FEED SCIENCE AND TECHNOLOGY}, author={Chavez, Stephen J. and Huntington, Gerald B.}, year={2013}, month={Aug}, pages={33–37} }
 @article{spears_whisnant_huntington_lloyd_fry_krafka_lamptey_hyda_2012, title={Chromium propionate enhances insulin sensitivity in growing cattle}, volume={95}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2011-4845}, abstractNote={Thirty-six Angus and Angus×Simmental heifers, averaging 291 kg, were used to determine the effects of dietary Cr, in the form of Cr propionate (Cr Prop), on glucose metabolism and serum insulin concentrations following glucose administration. Heifers were stratified by body weight (BW) within a breed and randomly assigned to treatments. Treatments consisted of 0, 3, 6, or 9 mg of supplemental Cr/d from Cr Prop. Based on dry matter (DM) intakes, the daily doses of Cr were equivalent to 0.47, 0.94, and 1.42 mg of supplemental Cr/kg of DM. Heifers were individually fed a corn silage-based diet at a level of 2% of BW. Each heifer was also fed 0.45 kg of a ground corn supplement daily that served as a carrier for supplemental Cr. Glucose tolerance tests were performed on d 44 of the study. Glucose was infused via jugular catheters at a level of 0.45 g/kg of BW(0.75) over a course of 1 to 2 min. Blood samples were collected at -10, 0, 5, 10, 15, 30, 45, 60, 90, 120, 150, and 180 min relative to glucose dosing for glucose and insulin determination. Area under the glucose response curve was lower (1,603 vs. 1,964 mg/dL per minute) in heifers supplemented with Cr from 0 to 45 min following glucose challenge. Serum insulin concentrations were lower in Cr-supplemented heifers than in controls following glucose infusion. The molar ratio of insulin to glucose was also lower in Cr-supplemented heifers relative to controls. Serum insulin and serum insulin to glucose ratios did not differ among heifers supplemented with 3, 6, or 9 mg of Cr/d. Results indicate that Cr Prop supplementation increased tissue sensitivity to insulin in growing heifers. Based on insulin sensitivity, Cr requirements (as Cr Prop) of growing heifers can be met by supplementing with 3 mg of Cr/d or 0.47 mg of Cr/kg of DM.}, number={4}, journal={JOURNAL OF DAIRY SCIENCE}, author={Spears, J. W. and Whisnant, C. S. and Huntington, G. B. and Lloyd, K. E. and Fry, R. S. and Krafka, K. and Lamptey, A. and Hyda, J.}, year={2012}, month={Apr}, pages={2037–2045} }
 @article{alvarez almora_huntington_burns_2012, title={Effects of supplemental urea sources and feeding frequency on ruminal fermentation, fiber digestion, and nitrogen balance in beef steers}, volume={171}, ISSN={["1873-2216"]}, DOI={10.1016/j.anifeedsci.2011.10.012}, abstractNote={The objective of two experiments was to evaluate non-protein N supplementation with protected urea sources in terms of rumen fermentation products, nutrient digestibility, and N balance in ruminally fistulated beef steers (initial bodyweight 239 ± 18 kg) fed switchgrass hay. Experiment 1 compared urea with Optigen II®, and Experiment 2 compared urea with RumaPro®. In both experiments, supplements (400 g/kg of daily dietary dry matter) were fed once daily or every 2 h in a balanced design. Supplements contained soybean hulls, corn grain, vitamins, and minerals as well as non-protein N sources. Non-protein N provided 0.18 g/g of dietary N. Switchgrass hay was fed once daily, at the same time as the supplement in the once-daily treatments. Dry matter intake (4.1 kg/d in Experiment 1, 4.5 kg/d in Experiment 2), dry matter digestibility (P<0.25, 0.58 ± 0.014 g/g in Experiment 1, 0.58 ± 0.010 g/g in Experiment 2), N balance (P<0.83, 11.3 ± 1.9 g/d in Experiment 1, 11.8 ± 3.6 g/d in Experiment 2), ruminal ammonia concentrations (P<0.29, 15.2 ± 1.4 mM in Experiment 1, 11.8 ± 0.6 mM in Experiment 2), and ruminal short-chain fatty acid concentrations (P<0.13, 77.7 ± 3.0 mM in Experiment 1, 75.4 ± 3.0 mM in Experiment 2) were not affected by feeding protected urea sources. Providing a steady supply of ruminally degradable N by feeding supplement every 2 h vs once daily decreased ruminal ammonia concentrations by approximately one-half by 4 h after feeding hay (P<0.01 in both experiments) and increased (P<0.02 in Experiment 1, P<0.08) in Experiment 2) apparent digestibility of dry matter (0.58–0.62 in Experiment 1, 0.56–0.61 in Experiment 2) and dietary fiber components.}, number={2-4}, journal={ANIMAL FEED SCIENCE AND TECHNOLOGY}, author={Alvarez Almora, E. G. and Huntington, G. B. and Burns, J. C.}, year={2012}, month={Feb}, pages={136–145} }
 @article{huntington_leonard_burns_2011, title={Technical note: Use of near-infrared reflectance spectroscopy to predict intake and digestibility in bulls and steers}, volume={89}, ISSN={["1525-3163"]}, DOI={10.2527/jas.2010-3376}, abstractNote={Multiple fecal samples were collected from growing Angus bulls (264 to 419 kg of BW, 3.0 to 11.4 kg/d of DMI) to predict DMI of a corn-silage-based diet. Contemporaneous digestion trials were conducted with the same diet in 12 steers in yr 1 to 3 and bulls in yr 4. Near-infrared spectra from fecal samples (n = 730 from 282 growing bulls, n = 240 from 36 steers and 12 bulls for digestion trials) were obtained from dried and ground fecal samples, and modified partial least squares regression was used to develop equations to predict DMI and DM digestibility (DMD). Although mean predicted DMI of the growing bulls (7.52 ± 0.04 kg/d or 22.4 ± 0.1 g/kg of BW) was within 2% of mean measured DMI (7.63 ± 0.06 kg/d or 22.7 ± 0.1 g/kg of BW), the mean of paired differences within samples (0.11 ± 0.04 kg/d or 0.3 ± 0.1 g/kg of BW) was greater (P < 0.01) than zero. Measured DMD (72.3 ± 0.5%) was identical (P < 0.97) to predicted DMD (72.3 ± 0.5%), and DMD for bulls in the digestion trial did not differ (P < 0.27) from DMD for steers. Prediction of intake requires incorporation of some measured values from the set of fecal samples to be predicted. Lack of similarity between spectra of fecal grab samples from the growing bulls and daily fecal collection of steers and bulls in the digestion trials in this study indicates the need for further verification before prediction of DMD with fecal grab samples.}, number={4}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Huntington, G. B. and Leonard, E. S. and Burns, J. C.}, year={2011}, month={Apr}, pages={1163–1166} }
 @article{chavez_huntington_burns_2011, title={Use of plant hydrocarbons as markers to estimate voluntary intake and digestibility in beef steers}, volume={139}, ISSN={["1871-1413"]}, DOI={10.1016/j.livsci.2011.01.012}, abstractNote={Calculating dry matter intake of grazing herbivores has been an issue in determining factors such as efficiency and digestibility of forages. Two experiments were conducted using alkanes to validate analytical methods with oven-dried and freeze-dried samples, compare and contrast measured and estimated intake, and to measure digestibility using a controlled-release capsule (CRC) or supplement. In the first trial, 7 beef steers consuming either alfalfa or switchgrass hay received either a CRC or supplement in a random crossover design. Each period lasted 20 days with fecal grab samples taken over the last 10 days and total fecal collection the last 5 days. In the second trial, 12 beef cattle were fed a blended switchgrass and alfalfa hay and fed a once-daily alkane supplement. Fecal grab samples were collected the last 5 days over the 14-day experiment. In the first experiment, steers fed switchgrass hay ate less and digested a smaller proportion of total diet (P < 0.02) than steers fed alfalfa. There was no difference (P < 0.35) between estimated intake and measured intake. Fecal concentrations of alkanes were not affected (P < 0.13) by drying method and no difference (P < 0.40) was seen between fecal grab samples and total fecal collection. Either dotriacontane (C32) or hexatriacontane (C36) can be used for estimating DMD. In the second experiment, there was no difference between measured and estimated intake (P < 0.35). There was no day effect between fecal concentrations and estimated intake. There was no difference (P < 0.65) between fecal alkane concentrations when duplicate samples were analyzed. Alkanes can be used to estimate intake in cattle. Fecal grab samples are sufficient to reduce labor and result in adequate estimated intake and daily feeding of alkanes can be used to replace the CRC.}, number={3}, journal={LIVESTOCK SCIENCE}, author={Chavez, S. J. and Huntington, G. B. and Burns, J. S.}, year={2011}, month={Aug}, pages={245–251} }
 @article{sauve_huntington_whisnant_burns_2010, title={Intake, Digestibility, and Nitrogen Balance of Steers Fed Gamagrass Baleage Topdressed at Two Rates of Nitrogen and Harvested at Sunset and Sunrise}, volume={50}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2009.02.0105}, abstractNote={ABSTRACT}, number={1}, journal={CROP SCIENCE}, author={Sauve, A. K. and Huntington, G. B. and Whisnant, C. S. and Burns, J. C.}, year={2010}, pages={427–437} }
 @article{freeman_poore_huntington_middleton_ferket_2009, title={Determination of nitrogen balance in goats fed a meal produced from hydrolyzed spent hen hard tissues}, volume={87}, ISSN={["0021-8812"]}, DOI={10.2527/jas.2008-1077}, abstractNote={To provide an economically viable and environmentally sound method for disposing of spent laying hens, we manufactured a proteinaceous meal from the hard tissue fraction of mechanically deboned laying hens (primarily feathers, bones, and connective tissue). We hydrolyzed the hard tissue and coextruded it with soybean hulls to create a novel feather and bone meal (FBM) containing 94.2% DM, 23.1% CP, 54.5% NDF, and 7.3% fat (DM basis). We evaluated the FBM in supplements for meat goats in which it provided 0, 20, 40, or 60% of the N added to the supplement compared with a negative control supplement with no added N source. The remainder of the N was contributed by soybean meal (SBM). Supplementation of N resulted in greater DMI than the negative control (P = 0.005), and DMI changed quadratically (P = 0.11) as FBM increased in the supplement. Digestibility of DM was similar in all diets, including the negative control (P > 0.10). Fiber digestibility increased linearly as dietary inclusion of FBM increased (P = 0.04 for NDF, P = 0.05 for ADF), probably as a result of the soybean hulls in the FBM. Nitrogen digestibility declined linearly from 60.5% with 0% FBM to 55.6% with 60% FBM (P = 0.07), but N retention changed by a quadratic function as FBM replaced SBM (P = 0.06). Negative control goats had less N digestibility (P < 0.001) and N retention (P = 0.008) than N-supplemented goats. Feather and bone meal had a greater proportion of ruminally undegradable B(3) protein than SBM (23.1 vs. 0.3% of CP, respectively). Ruminal VFA and pH were unaffected by replacing SBM with FBM, but supplying no source of N in the concentrate resulted in reduced total VFA in ruminal fluid (P = 0.04). Ruminal ammonia concentration increased quadratically (P = 0.07) as FBM increased, reflecting increased intake, and it was much less in unsupplemented goats (P < 0.001). Serum urea had less variation between 0 and 4 h after feeding in goats receiving 40 or 60% of added N as FBM in comparison with those receiving only SBM or 20% FBM. Feather and bone meal promoted a more stable rumen environment, possibly because of reduced rates of protein degradation within the rumen. A palatable by-product meal for ruminants can be made from spent laying hen hard tissue, one that supports N metabolism similar to that of traditional protein sources.}, number={3}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Freeman, S. R. and Poore, M. H. and Huntington, G. B. and Middleton, T. F. and Ferket, P. R.}, year={2009}, month={Mar}, pages={1068–1076} }
 @article{sauve_huntington_burns_2009, title={Effects of total nonstructural carbohydrates and nitrogen balance on voluntary intake of goats and digestibility of gamagrass hay harvested at sunrise and sunset}, volume={148}, ISSN={["1873-2216"]}, DOI={10.1016/j.anifeedsci.2008.03.001}, abstractNote={Abstract We evaluated differences in composition of Iuka gamagrass ( Tripsacum dactyloides L.) hay harvested at 06:00 (AM harvest) or 18:00 h (PM harvest), and measured how protein supplementation and time of harvest interact to affect the voluntary intake, digestibility, and N balance of goats. Boer cross wethers ( n  = 28; 24 kg) were randomly assigned to be fed supplement (310 g/kg of crude protein (CP), fed at 110 g/kg of dry matter (DM) intake, 14 goats) or no supplement (14 goats). Within supplemented or not supplemented groups, goats were randomly assigned to a crossover design of AM harvest (seven goats) or PM harvest (seven goats), and housed individually in metabolism crates with free access to water and mineral blocks. They were fed twice daily, with supplement offered 30 min prior to the morning feedings. After a 7-d adaptation, voluntary intake (goats were offered 1100 g/kg of previous day's intake) was measured for 14 d, followed by a 4-d adjustment phase to equalize DM offered between periods, and finally a 5-d digestion and balance phase. After Period 1, goats were switched to their new hay harvest times, and the protocol was repeated. Compared to the AM harvest, the PM harvest had higher (P versus 59.0 g/kg DM), monosaccharides (37.0 g/kg DM versus 28.6 g/kg DM), di- and polysaccharides (18.5 g/kg DM versus 15.4 g/kg DM) and less neutral detergent fiber (NDF, 700 g/kg versus 710 g/kg). Crude protein (79 g/kg DM) and starch (15.2 g/kg DM) were similar for the PM and AM harvest. Dry matter digestibility was higher (P versus AM harvests (555 g/kg DM versus 531 g/kg DM) and for supplemented versus not supplemented (563 g/kg DM versus 522 g/kg DM). Voluntary gamagrass DM intake (550 g/d versus 548 g/d) and calculated total digestible DM intake (327 g/d versus 313 g/d) were similar for the PM and AM harvest. However, total digestible DM intake during the digestion and balance phase was higher (P versus AM harvest (317 g/d versus 299 g/d). Time of harvest did not affect N intake, digestion, or calculated retention. Compared to no supplementation, the supplement improved (P versus 3.7 g/d) and retention (2.2 g/d versus 1.1 g/d). The PM harvest increased DM digested, largely TNC and digestible DM intake by goats due to increased TNC and not because of a 2% increase in DM intake. Providing a protein supplement had very limited effects on intake and digestibility of gamagrass.}, number={2-4}, journal={ANIMAL FEED SCIENCE AND TECHNOLOGY}, author={Sauve, A. K. and Huntington, G. B. and Burns, J. C.}, year={2009}, month={Jan}, pages={93–106} }
 @article{hill_hopkins_davidson_bolt_diaz_brownie_brown_huntington_whitlow_2009, title={The addition of cottonseed hulls to the starter and supplementation of live yeast or mannanoligosaccharide in the milk for young calves}, volume={92}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2008-1320}, abstractNote={The objectives of this study were to investigate the effects of the addition of cottonseed hulls (CSH) to the starter and the supplementation of live yeast product (YST) or mannanoligosaccharide product (MOS) to milk, on growth, intake, rumen development, and health parameters in young calves. Holstein (n = 116) and Jersey (n = 46) bull (n = 74) and heifer (n = 88) calves were assigned randomly within sex at birth to treatments. All calves were fed 3.8 L of colostrum daily for the first 2 d. Holstein calves were fed 3.8 L of whole milk, and Jersey calves were fed 2.8 L of whole milk through weaning at 42 d. Calves continued on trial through 63 d. Six treatments were arranged as a 2 x 3 factorial. Calves received either a corn-soybean meal-based starter (21% crude protein and 6% acid detergent fiber; -CSH) or a blend of 85% corn-soybean meal-based starter and 15% CSH (18% crude protein and 14% acid detergent fiber; +CSH) ad libitum. In addition, calves received whole milk with either no supplement (NONE) or supplemented with 3 g/d of mannanoligosaccharide product (MOS) or 4 g/d of live yeast product (YST) through weaning at 42 d. Twelve Holstein steers [n = 6 (per starter type); n = 4 (per supplement type)] were euthanized for collection and examination of rumen tissue samples. Dry matter intake (DMI) was greater for Holstein calves fed +CSH (0.90 kg/d) than -CSH (0.76 kg/d). Final body weight at 63 d of Holstein calves fed +CSH (75.8 kg) was greater than that of those fed -CSH (71.0 kg). Average daily gain (ADG) was greater for Holstein calves fed +CSH (0.58 kg/d) than -CSH (0.52 kg/d). However, Holstein calves fed -CSH had a greater feed efficiency (FE; 0.71 kg of ADG/kg of DMI) than those fed +CSH (0.65 kg of ADG/kg of DMI). Also, Holstein calves fed +CSH had narrower rumen papillae (0.32 mm) compared with those fed -CSH (0.41 mm). There were no significant effects of CSH on DMI, ADG, or FE in Jersey calves. There were no significant effects of YST or MOS on DMI, ADG, FE, or rumen papillae measures in Holstein calves. Jersey calves fed YST or MOS had greater final body weight at 63 d (51.2 kg and 51.0 kg, respectively) than calves fed NONE (47.5 kg). However, there were no significant effects of YST or MOS on DMI, ADG, or FE in Jersey calves.}, number={2}, journal={JOURNAL OF DAIRY SCIENCE}, author={Hill, S. R. and Hopkins, B. A. and Davidson, S. and Bolt, S. M. and Diaz, D. E. and Brownie, C. and Brown, T. and Huntington, G. B. and Whitlow, L. W.}, year={2009}, month={Feb}, pages={790–798} }
 @article{huntington_magee_matthews_poore_burns_2009, title={Urea metabolism in beef steers fed tall fescue, orchardgrass, or gamagrass hays}, volume={87}, ISSN={["1525-3163"]}, DOI={10.2527/jas.2008-1444}, abstractNote={Two experiments were conducted to assess effects of endophyte treatments (Exp. 1), forage species (Exp. 2), and supplementation (Exp. 2) on urea production, excretion, and recycling in beef steers. Infusion of (15,15)N-urea and enrichment of urea in urine samples were used to calculate urea-N entry and recycling to the gut. Acceptably stable enrichment of (15)N-urea in urine was obtained after 50 h of intrajugular infusion of (15,15)N-urea, indicating that valid data on urea metabolism can be obtained from steers fed forages twice daily. After adjustment by covariance for differences in N intake among treatments in Exp. 1, steers fed endophyte-infected tall fescue had less (P<0.10) urea-N entry, recycling to the gut, and return of recycled urea-N to the ornithine cycle than those fed endophyte-free or novel endophyte-infected tall fescue. However, urea-N urinary excretion or return to the gut was similar among endophyte treatments when expressed as a proportion of urea-N entry. Urea-N entry and return to the gut in Exp. 2 was similar in steers fed gamagrass or orchardgrass hay after adjustment by covariance for differences in N intake. Less (P<0.01) urinary excretion, expressed as grams per day or as a proportion of urea-N entry, with gamagrass than with orchardgrass was associated with faster in vitro NDF-N digestion with gamagrass. Supplementation of gamagrass or orchardgrass with 1.76 kg/d of readily fermentable fiber and starch decreased urea entry (P<0.06) and urinary excretion of urea (P<0.01). Interactions between hay source and supplement reflected a greater response to supplementation for steers fed orchardgrass than for those fed gamagrass. After adjustment for differences among treatments in N supply, results of both experiments support the concept of improved N use in response to increased carbohydrate fermentability in the rumen, due either to inherent differences in forage fiber or to supplementation with readily fermentable carbohydrate (starch or fiber). Closer coordination of ruminal fermentation of carbohydrate and N sources provided greater and more efficient capture of dietary N as tissue protein in forage-fed steers.}, number={4}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Huntington, G. B. and Magee, K. and Matthews, A. and Poore, M. and Burns, J.}, year={2009}, month={Apr}, pages={1346–1353} }
 @article{freeman_poore_huntington_middleton_2008, title={Evaluation of secondary protein nutrients as a substitute for soybean meal in diets for beef steers and meat goats}, volume={86}, ISSN={["0021-8812"]}, DOI={10.2527/jas.2006-0698}, abstractNote={Finding appropriate disposal techniques for waste products is one of many challenges facing the poultry-processing industry. One waste generated in significant quantities is dissolved air floatation sludge, a product of wastewater treatment. Converting dissolved air floatation sludge into a dry feed product (meal) for incorporation into livestock feed appears to be a viable solution. This meal, called secondary protein nutrients (SPN), is high in protein (45% CP), fat (28% crude fat), and minerals. The protein consists of 85% B(2) and B(3) fractions, which are moderately to slowly degradable in the rumen, and therefore may potentially escape ruminal degradation and be available for digestion in the lower gastrointestinal tract. The goal of this research was to evaluate SPN as an alternative to traditional protein sources for ruminants by substituting it on an equivalent N basis for soybean meal in cattle and meat goat diets (0, 25, 50, 75, and 100% for cattle; 0, 20, and 40% for goats). When included in corn silage-based steer diets, increasing SPN resulted in linear and quadratic declines in both DMI and ADG (P < 0.001). Dry matter intake diminished with inclusion rates above 50%, and ADG were reduced after inclusion of SPN reached 25% of added N. Feed efficiency (the reciprocal of the efficiency of gain, which is represented by G:F) declined linearly (P < 0.001) with each incremental increase in SPN. Addition of up to 40% added N as SPN in goat diets caused no change in DMI, digestibility of DM or fiber, or N retention. Ruminal VFA concentrations showed little variation in either species. Increasing the proportion of SPN in the feed caused linear declines in ruminal NH(3) in steers (P < 0.001). Increasing SPN in goat diets, however, resulted in only a trend toward reductions of this parameter (P = 0.14). The decreases observed may have resulted from decreasing ruminal protein degradability or increasing fat caused by increasing the proportion of SPN in the feed. Urinary urea N as a percentage of urinary N showed significant declines in cattle, but not in goats, over the ranges of SPN offered. These results indicate that SPN can be included in diets for ruminants to supply up to 40% of supplemental N with little negative impact on animal performance.}, number={1}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Freeman, S. R. and Poore, M. H. and Huntington, G. B. and Middleton, T. F.}, year={2008}, month={Jan}, pages={146–158} }
 @article{vibart_fellner_burns_huntington_green_2008, title={Performance of lactating dairy cows fed varying levels of total mixed ration and pasture}, volume={75}, ISSN={["1469-7629"]}, DOI={10.1017/S0022029908003361}, abstractNote={Two, 8-week experiments, each using 30 lactating Holstein cows, were conducted to examine performance of animals offered combinations of total mixed ration (TMR) and high-quality pasture. Experiment 1 was initiated in mid October 2004 and Experiment 2 was initiated in late March 2005. Cows were assigned to either a 100% TMR diet (100:00, no access to pasture) or one of the following three formulated partial mixed rations (PMR) targeted at (1) 85% TMR and 15% pasture, (2) 70% TMR and 30% pasture and (3) 55% TMR and 45% pasture. Based on actual TMR and pasture intake, the dietary TMR and pasture proportions of the three PMR in Experiment 1 were 79% TMR and 21% pasture (79:21), 68% TMR and 32% pasture (68:32), and 59% TMR and 41% pasture (59:41), respectively. Corresponding proportions in Experiment 2 were 89% TMR and 11% pasture (89:11), 79% TMR and 21% pasture (79:21) and 65% TMR and 35% pasture (65:35), respectively. Reducing the proportion of TMR in the diets increased pasture consumption of cows on all PMR, but reduced total dry matter intake compared with cows on 100:00. An increase in forage from pasture increased the concentration of conjugated linoleic acids and decreased the concentration of saturated fatty acids in milk. Although milk and milk protein yields from cows grazing spring pastures (Experiment 2) increased with increasing intakes of TMR, a partial mixed ration that was composed of 41% pasture grazed in the fall (Experiment 1) resulted in a similar overall lactation performance with increased feed efficiency compared to an all-TMR ration.}, number={4}, journal={JOURNAL OF DAIRY RESEARCH}, author={Vibart, Ronaldo E. and Fellner, Vivek and Burns, Joseph C. and Huntington, Gerald B. and Green, James T., Jr.}, year={2008}, month={Nov}, pages={471–480} }
 @article{huntington_burns_2008, title={The interaction of harvesting time of day of switchgrass hay and ruminal degradability of supplemental protein offered to beef steers}, volume={86}, ISSN={["0021-8812"]}, DOI={10.2527/jas.2006-701}, abstractNote={The objective of this study was to evaluate an interaction between harvest at 0600 (AM) vs. 1800 (PM) with high (HI) or low (LO) ruminal degradability of a protein supplement to change voluntary intake, digestion, or N retention by steers offered switchgrass (Panicum virgatum L.) hay. Black steers (255 +/- 14 kg of BW) were blocked by BW, and then randomly assigned (5 steers each) to AM/HI, PM/HI, AM/LO, or PM/LO treatment groups. Steers were group-housed in covered, outdoor pens with individual feeding gates. After adaptation and standardization, intake was measured for 21 d followed by a digestion trial (5 d of total collection). Steers were offered 767 (LO) or 825 (HI) g/d of supplement to provide 268 g of CP/d. Compared with AM, PM had greater (P = 0.01) concentrations of total nonstructural carbohydrate (TNC, 71 vs. 56 g/kg of DM), and lesser concentrations of NDF (760 vs. 770 g/kg of DM, P = 0.02), ADF (417 vs. 427 g/kg of DM, P = 0.02), and CP (55.9 vs. 58.6 g/ kg of DM, P = 0.07). Protein fractions A, B(2), and B(3) were similar for AM and PM, but HI contained more (P < 0.02) A (694 vs. 296 g/kg of protein) and less B(2) (174 vs. 554 g/kg of protein) fraction than LO. Harvest interacted with supplement to increase (P = 0.07) ad libitum digestible DMI for steers offered PM/HI (11.4 g/kg of BW daily) compared with steers offered PM/LO (10.2 g/kg of BW daily), but there was no difference for steers offered AM/LO or AM/HI (10.7 g/kg of BW). Apparent digestibilities of DM (594 vs. 571 g/kg of intake), NDF (591 vs. 562 g/kg of intake), ADF (585 vs. 566 g/kg of intake), and N (651 vs. 632 g/kg of intake) were greater (P < 0.04) for PM than for AM. Apparent digestibility of N was greater (P = 0.02) for HI (652 g/ kg of intake) vs. LO (631 g/kg of intake). Interactions between harvest and supplement for apparent digestibilities of NDF (P = 0.09) and ADF (P = 0.03) were due to no change or an increase in digestibility in response to increased ruminal degradability of supplement in steers offered PM harvest, whereas increased ruminal degradability of supplement decreased digestibility of NDF and ADF in steers offered AM harvest. Treatments did not affect hay intake (3.93 kg/d), N retained (15.8 g/d), or plasma urea N (5.25 mM) during ad libitum intake. Greater TNC in PM vs. AM harvest was not sufficient by itself to increase total voluntary DMI, but greater protein degradability interacted with harvest time to increase ruminal fiber digestibility and digestible DMI of beef steers offered PM vs. AM harvest.}, number={1}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Huntington, G. B. and Burns, J. C.}, year={2008}, month={Jan}, pages={159–166} }
 @article{huntington_burns_archibeque_2007, title={Urea metabolism in beef steers grazing Bermudagrass, Caucasian bluestem, or gamagrass pastures varying in plant morphology, protein content, and protein composition}, volume={85}, ISSN={["0021-8812"]}, DOI={10.2527/jas.2006-597}, abstractNote={Pastures of Bermudagrass (Cynodon dactylon, BG), Caucasian bluestem (Bothriochloa caucasica, CBS), and gamagrass (Tripsacum dactyloides, GG) were evaluated from the perspectives of forage composition, selection during grazing, and N metabolism in beef steers. All pastures were fertilized with 78 kg/ha of N approximately 60 and 30 d before sample collection. In 2000 and 2001, 12 steers (250 kg of BW) were blocked based on BW and then assigned randomly to a replicated, randomized complete block design, with 2 pastures of each forage and 2 steers per pasture. Three other steers with esophageal fistulas were used to collect masticate samples to represent intake preferences. Herbage mass was >1,900 kg/ha. After at least 14 d of adaptation, urine and blood samples were collected for determination of serum urea N and percentage of urinary N in the form of urea. One steer per pasture (6 steers per year) was infused i.v. with (15,15)N urea for 50 h before collecting urine for 6 h to measure urea N enrichment, urea entry rate, urinary urea excretion, gut urea recycling, and return of urea N to the ornithine cycle. The canopy leaf:stem DM ratio differed (P = 0.01) among BG (0.50), CBS (1.01), and GG (4.00). Caucasian bluestem had less CP (% of DM) than GG or BG in the canopy (9.6 vs. 12.0 or 12.3, P = 0.07) and in the masticate (9.8 vs. 14.7 or 13.9, P = 0.04). Bermudagrass had less true protein (% of CP) than CBS or GG in the canopy (72.9 vs. 83.3 or 83.0, P = 0.07) and in the masticate (73.7 vs. 85.8 or 88.0, P = 0.04). Compared with GG and BG, CBS had less serum urea N (10.1 or 12.2 vs. 2.5 mM, P = 0.01), urea entry rate (353 or 391 vs. 209 mmol of N/h, P = 0.07), and urinary urea excretion (105 or 95 vs. 18 mmol of N/h, P = 0.04), and a greater return of urea N to the ornithine cycle as a proportion of gut urea recycling (0.109 or 0.118 vs. 0.231, P = 0.02). Urea production and recycling in these steers responded more to the N concentration in the grasses than to differences in plant protein fractions. There was no evidence of improved N capture by the steers due to changes in the leaf:stem ratio among the grasses at the herbage mass evaluated.}, number={8}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Huntington, G. B. and Burns, J. C. and Archibeque, S. L.}, year={2007}, month={Aug}, pages={1997–2004} }
 @article{huntington_harmon_kristensen_hanson_spears_2006, title={Effects of a slow-release urea source on absorption of ammonia and endogenous production of urea by cattle}, volume={130}, ISSN={["0377-8401"]}, DOI={10.1016/j.anifeedsci.2006.01.012}, abstractNote={Three experiments were conducted with Angus or Holstein steers to evaluate effects of dietary urea–calcium (a slow rumen-release urea source) on absorption of ammonia N from the gut and urea N production in the liver. Steers were fed a high-grain diet (Experiment 1) or an all-forage diet (Experiments 2 and 3). Urea or urea–calcium (0.25 g/kg body weight) was dosed into the esophagus (Experiments 1 and 2) or rumen (Experiment 3), and blood samples were serially collected for 180 min. Blood concentrations of ammonia N and urea N were measured in all experiments, and net flux of metabolites across splanchnic tissues was measured in Experiment 3. Compared to urea, urea–calcium reduced (P<0.05) plasma concentrations of ammonia N in steers fed all-forage diets, and tended (P<0.06) to reduce arterial glucose concentrations in Experiment 3. Plasma concentrations of urea N were not affected by treatment in any experiment. Treatment and time post-dosing interactions (P<0.05) in Experiment 3 were due to increased ruminal fluid concentrations of ammonia N, net release of ammonia N by portal-drained viscera and total splanchnic tissues with urea versus urea–calcium treatment shortly after dosing. Similar interactions (P<0.05) indicated that urea caused higher hepatic glucose release and increased l-lactate release by total splanchnic tissues after dosing than urea–calcium. Urea–calcium was effective in mitigating rapid ammonia release in the rumen and subsequent effects on glucose and lactate metabolism.}, number={3-4}, journal={ANIMAL FEED SCIENCE AND TECHNOLOGY}, author={Huntington, G. B. and Harmon, D. L. and Kristensen, N. B. and Hanson, K. C. and Spears, J. W.}, year={2006}, month={Nov}, pages={225–241} }
 @article{matthews_poore_huntington_green_2005, title={Intake, digestion, and N metabolism in steers fed endophyte-free, ergot alkaloid-producing endophyte-infected, or nonergot alkaloid-producing endophyte-infected fescue hayI}, volume={83}, DOI={10.2527/2005.8351179x}, abstractNote={A digestion and N balance trial was conducted to compare effects of traditional endophyte-infected (E+), endophyte-free (E-), and nontoxic endophyte infected (NE; MaxQ; Pennington Seed, Inc., Madison, GA) Jesup tall fescue (Festuca arundinacea Schreb.) hay on digestion and N retention in steers. Hay composition (DM basis) was as follows: E+ (10.8% CP, 59.9% NDF, and 29.4% ADF), E- (11.8% CP, 58.5% NDF, and 28.4% ADF), and NE (11.6% CP, 58.6% NDF, and 28.3% ADF). Eight Polled Hereford steers (initial BW 240 +/- 9 kg) were used in a replicated, 3 x 3 Latin square design, with an extra steer allotted to each square. Steers were fed ad libitum for 14 d, followed by a 9-d adaptation to restricted intake (based on the animal with the lowest ad libitum intake for the square) and a 5-d fecal and urine collection. Water intake (20.2 L/d) and urine output (7.40 L/d) did not differ (P > 0.10) during the collection period. Plasma prolactin concentration was less (P < 0.05) for steers on the E+ hay (8.83 ng/mL) than for those on the E- hay (18.03 ng/mL) and intermediate for steers on the NE hay (12.65 ng/mL). Endophyte-infected hay differed (P < 0.05) from E- and NE in ad libitum DMI (5.02 vs. 5.62 and 5.61 kg/d, respectively) and ad libitum DMI as a percentage of BW (1.86 vs. 2.06 and 2.06%, respectively). Restricted DMI during the fecal and urine collection was lower (P < 0.05) for E+ hay than for E- (5.04 vs. 5.24 kg/d), and NE was intermediate (5.19 kg/d). Dry matter digestibility was lower (P < 0.05) for E+ compared with E- and NE (62.3 vs. 67.0 and 65.9%, respectively). Digestibility of ADF was lower (P < 0.05) for E+ than for E-, and was intermediate for NE (61.5, 66.0, and 63.9%, respectively). There were no differences for NDF, cellulose, or hemicellulose digestibilities among hay types. Crude protein digestibility was higher (P < 0.05) for E- and NE than for E+ (54.3 and 52.5 vs. 48.1%, respectively). Nitrogen retention was lower (P < 0.01) for E+ than for E- or NE (15.6 vs. 22.7 or 23.0 g/d, respectively). Hay type did not influence plasma urea N, urine urea N output, or urine urea N as a percentage of urinary N. Results from this study indicate that E+ tall fescue hay was lower in ad libitum DMI, DM digestibility, and N retention than NE or E- hays with similar chemical composition. Hay from NE and E- fescue had nearly identical composition, and did not differ for any variable measured.}, number={5}, journal={Journal of Animal Science}, author={Matthews, A. K. and Poore, M. H. and Huntington, G. B. and Green, J. T.}, year={2005}, pages={1179–1185} }
 @article{magee_poore_burns_huntington_2005, title={Nitrogen metabolism in beef steers fed gamagrass or orchardgrass hay with or without a supplement}, volume={85}, ISSN={["1918-1825"]}, DOI={10.4141/a04-045}, abstractNote={ A 50:50 soybean hull:corn grain supplement fed at 0.75% of body weight (BW) decreased ad libitum gamagrass or orchardgrass hay intake by steers, but increased total dry matter (DM) intake, DM digestibility, N intake, and N retained. Supplementation had a greater effect on N metabolism in steers fed orchardgrass than steers fed gamagrass. Key words: Steers, beef, hulls, soybean, metabolism, nitrogen }, number={1}, journal={CANADIAN JOURNAL OF ANIMAL SCIENCE}, author={Magee, KJ and Poore, MH and Burns, JC and Huntington, GB}, year={2005}, month={Mar}, pages={107–109} }
 @article{hill_hopkins_davidson_bolt_diaz_brownie_brown_huntington_whitlow_2005, title={Technical note: Technique for dissection and analysis of the rumen in young calves}, volume={88}, ISSN={["1525-3198"]}, DOI={10.3168/jds.S0022-0302(05)72691-6}, abstractNote={This paper discusses a technique used to evaluate rumen development in young calves, including removal, dissection, and analysis of tissue. The method allowed for examination of the different sacs of the rumen (dorsal, ventral, cranial, and caudal) using scanning electron microscopy to measure papillae denseness and histology slides to measure papillae length and width. Computer software was used to produce accurate measurements of papillae. The rumens of young calves were dissected, and samples were taken from the cranial, caudal, ventral, and dorsal sections. Calves were part of a nutrition research study, and dietary treatments did have an effect on development measurements such as length, width, and papillae denseness.}, number={1}, journal={JOURNAL OF DAIRY SCIENCE}, author={Hill, SR and Hopkins, BA and Davidson, S and Bolt, SM and Diaz, DE and Brownie, C and Brown, T and Huntington, GB and Whitlow, LW}, year={2005}, month={Jan}, pages={324–326} }
 @article{richards_swanson_paton_harmon_huntington_2003, title={Pancreatic exocrine secretion in steers infused postruminally with casein and cornstarch}, volume={81}, DOI={10.2527/2003.8141051x}, abstractNote={Our objective was to evaluate the effect of postruminal protein infusion on pancreatic exocrine secretions. One Holstein, two crossbred, and five Angus steers (305 +/- 5 kg) with pancreatic pouch-duodenal reentrant cannulas and abomasal infusion catheters were used in a replicated 4 x 4 Latin square. All steers were abomasally infused with 1,050 g/d of raw cornstarch with treatments of 0, 60, 120, or 180 g/d of sodium casein suspended in water to yield 6,000 g/d of infusate daily. Steers were limit-fed (1.5 x NEm; 12 equal portions daily) a 90% corn silage, 10% supplement diet formulated to contain 12.5% CP. Periods consisted of 3 d of adaptation to infusion, 7 d of full infusion, 1 d of collection, and 7 d of rest. Pancreatic juice was collected in 30-min fractions continuously for 6 h. Total juice secreted and the pH of individual fractions were recorded, a 10% subsample was retained to form a composite sample, and remaining fluid was returned to the duodenum. Juice composite samples were stored (-30 degrees C) until analyzed for total protein and activities of alpha-amylase, trypsin, and chymotrypsin. Casein infusion linearly increased alpha-amylase concentration (182 to 271 units/mL; P < 0.02; 17.5 to 24.6 units/mg of protein; P < 0.03) and secretion rate (26,847 to 41,894 units/h; P < 0.01). Total juice secretion (155 g/h), pH of pancreatic juice (8.13), secretion rate of protein (1,536 mg/h), and concentration of protein (10.2 mg/mL) in pancreatic secretions were not affected (P > 0.05) by casein infusion. Similarly, casein infusion did not change 0.05) trypsin and chymotrypsin concentrations (1,379 and 349 units/L or 0.134 and 0.033 units/mg of protein, respectively) or secretion rates (206 and 52 units/h, respectively). Abomasal infusion of protein with starch stimulated a greater pancreatic secretion of alpha-amylase activity into the intestine than infusion of starch alone.}, number={4}, journal={Journal of Animal Science}, author={Richards, C. J. and Swanson, K. C. and Paton, S. J. and Harmon, D. L. and Huntington, G. B.}, year={2003}, pages={1051–1056} }
 @article{richards_branco_bohnert_huntington_macari_harmon_2002, title={Intestinal starch disappearance increased in steers abomasally infused with starch and protein}, volume={80}, DOI={10.2527/2002.80123361x}, abstractNote={Steers (379 +/- 10 kg) with ruminal, duodenal, and ileal cannulas were used in a 5 x 5 Latin square digestion trial to quantify and evaluate the relationship between intestinal protein supply and intestinal starch disappearance. Treatments were infusions of 0, 50, 100, 150, or 200 g/d of casein along with 1,042 g/d of raw cornstarch. Abomasal infusions were accomplished by passing tubing and a pliable retaining washer through the reticular-omasal orifice into the abomasum. Steers were fed a 93% corn silage, 7% supplement diet that contained 12% crude protein at 1.65% body weight in 12 equal portions/d. Periods lasted 17 d (12 d for adaptation, 2 d of collections, and 3 d of rest). The quantity and percentage of organic matter and protein disappearance from the small intestine increased linearly (P < 0.03) with infused casein. Greater quantities of starch disappeared with increased casein infusion (P < 0.01). The infusion of 200 g/d of casein increased small intestinal starch disappearance by 226 g/d over the control. Casein infusion did not affect the quantity or percent of organic matter, starch, or protein disappearance in the large intestine. Treatments did not change ruminal ammonia N, ruminal pH, or plasma glucose concentrations. Starch disappearance from the small intestine was increased with greater protein flow to the duodenum of steers.}, number={12}, journal={Journal of Animal Science}, author={Richards, C. J. and Branco, A. F. and Bohnert, D. W. and Huntington, G. B. and Macari, M. and Harmon, D. L.}, year={2002}, pages={3361–3368} }
 @article{archibeque_burns_huntington_2002, title={Nitrogen metabolism of beef steers fed endophyte-free tall fescue hay: Effects of ruminally protected methionine supplementation}, volume={80}, DOI={10.2527/2002.8051344x}, abstractNote={Level of nitrogen (N) intake and ruminally protected methionine supplementation were evaluated in eight Angus growing steers (initial BW 253+/-21 kg, final BW 296+/-21 kg) in a replicated 4+/-4 Latin square design. The steers were fed two endophyte-free tall fescue (Festuca arundinacea) hays that contained 2.2 (LO) or 2.8% (HI) of DM as N and were either supplemented or not with ruminally protected methionine (10 g metabolizable methionine/d). Diets were fed to provide adequate energy for 0.5 kg ADG and sufficient protein for maintenance (LO), or protein to support 0.5 kg ADG (HI). Following at least 14 d of adjustment, N balance was measured for 6 d. Isotopic urea was infused (15N15N-urea, 0.164 mmol urea N/h) via a jugular catheter for 56 h and urine was collected from 48 to 56 h to measure urea kinetics. Jugular blood was collected during the balance trial, and serum was analyzed for serum urea N (SUN). By design, daily N intake was greater (P < 0.05) for HI (112 g) than for LO (89 g). Compared with LO, steers when fed HI had greater (P < 0.05) daily DMI (4,217 vs 4,151 g), fecal N (34.4 vs 31.2 g), N digested (77.1 vs 57.7 g), urine N (48.3 vs 37.5 g), urine urea N excretion (34.6 vs 24.8 g), and N retained (29.8 vs 21.1 g). When fed HI steers also had higher (P < 0.05) urine urea N concentration (276 vs 219 mM), SUN (8.7 vs 6.7 mM), N digestibility (69.1 vs 64.9%), percentage of urinary N present as urea (71.5 vs 66.7%, P < 0.053), and rate of urea N production (59.6 vs 49.2 g/d) but lower (P < 0.05) percentage of urea N produced that was returned to the ornithine cycle (15.03 vs 19.2 1%) than when fed LO. Methionine supplementation decreased daily urine N (41.2 vs 44.6 g, P = 0.10) and increased both the amount of N retained daily (27.9 vs 23.7 g, P < 0.089) and the percentage of N digested that was retained (40.4 vs 34.6%, P < 0.094). In summary, supplemental methionine met a specific dietary limitation by increasing the amount of digested N that was retained by the steers.}, number={5}, journal={Journal of Animal Science}, author={Archibeque, S. L. and Burns, J. C. and Huntington, G. B.}, year={2002}, pages={1344–1351} }
 @article{huntington_poore_hopkins_spears_2001, title={Effect of ruminal protein degradability on growth and N metabolism in growing beef steers}, volume={79}, DOI={10.2527/2001.792533x}, abstractNote={The objective of two experiments was to correlate plasma levels of urea N (PUN) and the percentage of urine N in the form of urea (UUN) to weight gain in response to different dietary protein regimens for growing Angus steers. In Exp. 1, 60 steers (302 kg BW) were assigned to various levels of dietary N (control plus supplemental N to provide from 100 to 400 g more crude protein daily) within two sources of supplemental N (soybean meal [SBM] or a mixture of two parts corn gluten meal:one part blood meal [CGM:BM]). In Exp. 2, 27 steers (229 kg BW) were fed two levels of SBM, and half of the steers received growth-promoting implants. Steers were housed in groups of 12 and fed individually for 84 d in both experiments. Corn silage was fed at a restricted rate to minimize orts. Jugular blood and urine samples were collected during the experiments. In Exp. 1, maximal ADG of steers fed SBM (1.0 kg) was reached with 671 g/d total crude protein, or 531 g/d metabolizable protein. Maximal ADG of steers fed CGM:BM (0.91 kg) was reached with 589 g/d total crude protein, or 539 g/d metabolizable protein. The DMI was higher (P < 0.07) for steers fed SBM (6.37 kg/d) than for steers fed CGM:BM (6.14 kg/d). Increasing ruminal escape protein from 36% (SBM) to 65% (CGM:BM) of CP decreased (P < 0.05) endogenous production of urea, as evidenced by lower concentrations of urea in blood and lower UUN. In Exp. 2, increasing supplemental protein from 100 to 200 g/d increased (P < 0.05) ADG and PUN. Implants lowered (P < 0.05) UUN, particularly at the higher level of supplemental protein. Protein supplementation of growing steers can be managed to maintain acceptable ADG yet decrease excretion of urea in the urine.}, number={2}, journal={Journal of Animal Science}, author={Huntington, G. and Poore, M. and Hopkins, B. and Spears, J.}, year={2001}, pages={533–541} }
 @article{archibeque_burns_huntington_2001, title={Urea flux in beef steers: Effects of forage species and nitrogen fertilization}, volume={79}, DOI={10.2527/2001.7971937x}, abstractNote={The effects of two forage species and N levels on urea kinetics and whole-body N metabolism were evaluated in eight Angus steers (initial BW 217+/-15 kg). In a replicated, 4 x 4 Latin square design, steers were fed gamagrass (Tripsacum dactyloides L.) or switchgrass (Panicum virgatum L.), each of which had 56.2 (LO) or 168.5 (HI) kg of N fertilization per hectare. Diets provided adequate energy for 0.5 kg ADG. Nitrogen balance and urea kinetics were measured from d 22 to 27 of each period. Urine samples collected during intravenous infusion of bis 15N urea were used to calculate production and recycling of urea N from relative abundance of urea isotopomers. Jugular blood serum was analyzed for serum urea N (SUN). Gamagrass differed from switchgrass (P < 0.05) in daily DMI (4,273 vs 4,185 g), N intake (72 vs 67 g), DM digestibility (61.0 vs 63.6%), fecal N (30.6 vs 28.3 g/d), urine urea N (10.5 vs 8.0 g/d), and percentage of urinary N present as urea N (53.5 vs 40.0%). After adjustment for differences in N intake, fecal N still tended to be greater (P < 0.09) for gamagrass than for switchgrass. The LO differed from the HI (P < 0.01) in daily N intake (63 vs 76 g), DM digestibility (61.3 vs 63.3%), urine N (13.6 vs 25.9 g/d), and N retained as a percentage of N digested (57.3 vs 43.5%). Compared to switchgrass, gamagrass had greater SUN, N digestibility, and N digested as N level increased (forage x N level interactions, P < 0.05). As N level increased, N retention increased from 19.5 to 23.5 g/d in gamagrass and decreased from 20.5 to 18.1 g/d in switchgrass (interaction, P < 0.07). The HI group was greater than the LO intake group (P < 0.03) in endogenous production of urea N (44.4 vs 34.0 g/d), gut entry rate of urea N (31.6 vs 28.2 g/d), and the amount of urea N that re-entered the ornithine cycle (9.4 vs 7.9 g/d). However, the percentage of urea N entering the gastrointestinal tract that was recycled was constant among treatments (29.1%), indicating that almost 70% of the urea N that entered the gastrointestinal tract was potentially available for anabolic purposes of the steers as a component of microbial products that were absorbed or excreted in the feces. In summary, N levels affected N metabolism of steers more when they were fed gamagrass than when they were fed switchgrass. Although the absolute amounts of N moving through the system changed with variations in intake, the proportions remained similar, with a greater efficiency of N use at low N intakes.}, number={7}, journal={Journal of Animal Science}, author={Archibeque, S. L. and Burns, J. C. and Huntington, G. B.}, year={2001}, pages={1937–1943} }
 @article{huntington_2000, title={High-starch rations for ruminant production discussed.}, volume={72}, number={20}, journal={Feedstuffs}, author={Huntington, G. B.}, year={2000}, pages={12–13} }
 @article{ludden_harmon_huntington_larson_axe_2000, title={Influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide on ruminant nitrogen metabolism: II. Ruminal nitrogen metabolism, diet digestibility, and nitrogen balance in lambs}, volume={78}, DOI={10.2527/2000.781188x}, abstractNote={Three lamb metabolism experiments were conducted to investigate the effects of chronic administration of the novel urease inhibitor N (n-butyl) thiophosphoric triamide (NBPT) on ruminal N metabolism, fermentation, and N balance. In Exp. 1, ruminally cannulated wethers (n = 28; 45.0 +/- .9 kg) were administered one of seven doses of NBPT (0 [control], .125, .25, .5, 1, 2, or 4 g of NBPT daily) and fed a common cracked corn/cottonseed hull-based diet twice daily containing 2% urea at 2.5% of initial BW for the duration of the 15-d experiment. Overall, NBPT decreased (linear P < .0001; quadratic P < .001) ruminal urease activity, resulting in linear increases (P < .0001) in ruminal urea and decreases in ruminal NH3 N concentrations. However, the detection of an NBPT x day interaction (d 2 vs 15; P < .01) indicated that this depression in urea degradation diminished as the experiment progressed. Increasing NBPT linearly decreased (P < .01) total VFA concentrations on d 2 of the experiment, but it had no effect (P > .10) on d 15. Increasing NBPT had no effect (P > .10) on DM or ADF digestibilities, but it linearly decreased (P < .01) N digestibility. Supplementing NBPT produced a linear increase (P < .05) in urinary N excretion and a linear decrease (P < .01) in N retention. In Exp. 2, ruminally cannulated wethers (n = 30; 46.8 +/- .6 kg) were fed one of two basal diets (2.0 vs 1.1% dietary urea) at 2.5% of initial BW and dosed with either 0 (control), .25, or 2 g of NBPT daily for the duration of the 15-d experiment. There were no NBPT x dietary urea interactions (P > .10) for Exp. 2. Increasing NBPT depressed (linear and quadratic P < .0001) ruminal urease activity, producing linear (P < .0001) increases in urea N and linear decreases in NH3 N in the rumen. As in Exp. 1, an NBPT x day interaction (P < .05) was noted for urea, NH3 N, and total VFA concentrations; the maximum response to NBPT occurred on d 2 but diminished by d 15 of the experiment. Administration of NBPT did not influence (P > .10) DM, ADF, or N digestibilities in Exp. 2. In Exp. 3, wether lambs (n = 30; 26.4 +/- .7 kg) were subjected to the same treatment regimen as in Exp. 2 for a 14-d N balance experiment. Although several NBPT x dietary urea interactions (P < .05) were noted, increasing NBPT did not affect (P > .10) N digestibility. Administration of NBPT quadratically increased (P < .10) urinary N excretion, producing a linear decrease (P < .05) in N retention. These results suggest that although NBPT is capable of inhibiting ruminal urease short-term, the ruminal microflora may be capable of adapting to chronic NBPT administration, thereby limiting its practical use in improving the utilization of dietary urea.}, number={1}, journal={Journal of Animal Science}, author={Ludden, P. A. and Harmon, D. L. and Huntington, G. B. and Larson, B. T. and Axe, D. E.}, year={2000}, pages={188–198} }
 @article{bach_huntington_calsamiglia_stern_2000, title={Nitrogen metabolism of early lactation cows fed diets with two different levels of protein and different amino acid profiles}, volume={83}, ISSN={["0022-0302"]}, DOI={10.3168/jds.s0022-0302(00)75152-6}, abstractNote={Four multiparous Holstein cows (569+/-122 kg) surgically prepared with indwelling catheters in the mesenteric, portal, and hepatic veins and carotid artery were allocated in a 4 x 4 Latin square to determine the effects of dietary crude protein (CP) level and amino acid (AA) profile on N metabolism during early lactation (from 25 to 65 d in milk). Cows received their diets in two equal meals and were milked twice daily. The dietary treatments were: 18% CP with a high (18H) or a low (18L) quality AA profile, and 15% CP with a high (15H) or a low (15L) quality AA profile. The four diets were similar in net energy for lactation (1.75 NEL Mcal/kg) and contained the same amount of RUP (34% of CP). The quality of the AA profile pertained only to the essential AA (EAA), and was assessed by comparison with the EAA profile of casein and considered the potential contribution of EAA from ruminal bacteria. The 18H and 15H diets were supplemented with 50 and 25 g/d of ruminally protected Met, respectively. After 10 d on treatment, a blood flow marker (p-amino-hippurate) was infused into a mesenteric vein, and arterial, portal, hepatic, and mammary blood samples were obtained at 3, 6, and 12 h after feeding. Dry matter intake was similar across treatments (23.4+/-0.5 kg/d). Amino acid oxidation, and consequent urea production, in the liver were numerically greater with the 18% CP rations, and, as a result, arterial urea concentrations were greatest (P < 0.01) with these rations. The amount of total AA extracted by the mammary gland tended to be greater with the H than with the L diets (21.4 vs. 18.2 mmol/ h, respectively). Milk yield tended to be greater (P = 0.16) with the 18H and 15H diets (47.7 and 46.3 kg/d, respectively) compared with the 18L and 15L diets (45.9 and 44.6 kg/d, respectively). Also, milk CP and casein contents were greatest (P = 0.09) with the H diets compared with the L diets. Milk and plasma urea N were greatest (P < 0.01) with the 18% CP diets. The efficiency of N utilization for milk protein synthesis was greatest (P < 0.09) with the 15% CP diets. It is concluded that milk protein production during early lactation is less susceptible to variations in dietary CP contents than variations in the AA profile of the dietary protein.}, number={11}, journal={JOURNAL OF DAIRY SCIENCE}, author={Bach, A and Huntington, GB and Calsamiglia, S and Stern, MD}, year={2000}, month={Nov}, pages={2585–2595} }
 @article{bach_huntington_stern_2000, title={Response of nitrogen metabolism in preparturient dairy cows to methionine supplementation}, volume={78}, DOI={10.2527/2000.783742x}, abstractNote={Three multiparous Holstein cows (607 kg of BW) were surgically prepared with an elevated carotid artery and indwelling catheters in the hepatic, portal, and two mesenteric veins to study the effects of methionine supplementation on amino acid metabolism during the last 2 wk of pregnancy. The study began 15 d before the expected calving date. Dietary treatments were Control (1.53 Mcal NE(l)/kg, 15.6% CP, and 40% ruminally undegradable protein) and Control supplemented with 60 g/d of ruminally protected methionine (MET, supplying 39 g/d of DL-methionine and approximately 18 g/d of methionine available for intestinal absorption). Each cow received both dietary treatments in a crossover design. Cows were fed once daily. After 5 d on treatment, a blood flow marker (para-aminohippurate) was infused into a mesenteric vein, and arterial, portal, and hepatic blood samples were obtained at 0, 2, 6, 12, and 18 h after feeding. Net flux of methionine was calculated as the plasma arteriovenous difference multiplied by plasma flow. Dry matter intake (10.8 kg/d) and portal (824 L/h) and hepatic (995 L/h) plasma flows were not affected (P > .10) by treatment. Arterial plasma concentration of methionine was greater (P = .10) with MET (27.67 microM) than with Control (16.42 microM). Net portal absorption of methionine increased (P = .10) with MET (26.2 g/d) compared with Control (9.5 g/d). The net portal methionine flux was negatively correlated (r = -.59; P < .001) with arterial urea concentrations. Net flux of methionine across splanchnic tissues shifted (P = .06) from a net uptake with Control (4 g/d) to a net output with MET (11 g/d). Therefore, MET increased by 15 g/d the methionine supply to the rest of the body. The net uptake of methionine by splanchnic tissues observed with Control indicated a net mobilization of methionine by peripheral tissues. Results indicate that methionine was the limiting amino acid with Control and that MET was beneficial because it increased methionine supply to peripheral tissues and reduced arterial urea concentrations.}, number={3}, journal={Journal of Animal Science}, author={Bach, A. and Huntington, G. B. and Stern, M. D.}, year={2000}, pages={742–749} }
 @article{huntington_1999, title={Sources of variation in splanchnic blood flow in steers}, volume={77}, DOI={10.2527/1999.77113031x}, abstractNote={Data from six experiments were used to describe sources of variation in blood flow through portal-drained viscera and liver of 33 steers that were fed equal-sized meals every 2 h. The experiments were designed to create "steady-state" conditions under which response to various dietary or physiological treatments was assessed. Sums of squares for blood concentration of blood flow marker, venoarterial differences in blood flow marker, and blood flow were divided into variation attributable to steer; period (or time); the steer x period interaction; sampling days within steer and period; and replications (or samplings) within day, steer, and period. Steer was the largest single source of variation in arterial concentration of blood flow marker, accounting for from 42 to 80% of sums of squares among the experiments. However, replication within day, steer, and period accounted for more variation than steer in portal or hepatic blood flow in four of the six experiments. When balanced for treatment effects, steer accounted for 59%, period and the steer x period interaction accounted for 14%, and replication accounted for 27% of variation in portal blood flow. Corresponding percentages for hepatic blood flow were 45, 20, and 35%. I conclude that steer and replication within steer x period cells in a matrix of treatments are the two largest sources of variation and that there is more variation among samples on a given day within steer x period cells than among days in the same cells.}, number={11}, journal={Journal of Animal Science}, author={Huntington, G. B.}, year={1999}, pages={3031–3036} }
 @article{knowlton_dawson_glenn_huntington_erdman_1998, title={Glucose metabolism and milk yield of cows infused abomasally or ruminally with starch}, volume={81}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(98)75889-8}, abstractNote={The effect of ruminal or abomasal starch infusion on milk yield and glucose metabolism of early lactation cows was measured. Four cows were continuously infused in the rumen or abomasum with partially hydrolyzed starch (1500 g/d) or were not infused (control) for three 14-d periods during wk 4 to 12 postpartum. Milk yield averaged over 40 kg/d throughout the experiment. Milk and milk lactose yields tended to increase when starch was infused and DMI was decreased, regardless of the site of infusion. Starch infusion increased mean insulin concentration and tended to decrease the concentration of serum nonesterified fatty acids. Ruminal starch infusion did not affect glucose irreversible loss rate but tended to increase glucagon concentration and decrease glucose oxidation. The increased milk yield that occurred when starch was infused ruminally relative to the milk yield of control cows could be a result of increased microbial protein supply or increased energy availability. Compared with ruminal starch infusion, abomasal starch infusion tended to increase the irreversible loss rate of glucose and to increase glucose oxidation. Abomasal infusion tended to increase plasma insulin concentration and to decrease the nonesterified fatty acid concentration relative to ruminal infusion. Infusion of starch abomasally resulted in increases of most uses of glucose, including milk lactose production, glucose oxidation, and the possible storage of glucose as body fat, which indicates that the early lactation dairy cow has a greater capacity for glucose metabolism than is provided by voluntary feed intake of average diets, but that not all available glucose is partitioned to the mammary gland. These data should be useful in testing current concepts and equations in nutritional and metabolic models of dairy cattle.}, number={12}, journal={JOURNAL OF DAIRY SCIENCE}, author={Knowlton, KF and Dawson, TE and Glenn, BP and Huntington, GB and Erdman, RA}, year={1998}, month={Dec}, pages={3248–3258} }
 @article{eisemann_huntington_catherman_1997, title={Insulin sensitivity and responsiveness of portal drained viscera, liver, hindquarters, and whole body of beef steers weighing 275 or 490 kilograms}, volume={75}, DOI={10.2527/1997.7582084x}, abstractNote={Our objective was to quantify effects of age, weight, and body composition on responsiveness (Rmax or Rmin) and sensitivity (ED50) of several parameters of glucose metabolism to insulin in growing beef steers. Steers ate equal-sized meals every 2 h; the diet contained 62% concentrate and sustained 1 kg ADG. Treatments were euglycemic clamps at 10, 20, 40, 80, 160, and 320 mU.h-1.kg BW-1 of insulin infused into a mesenteric vein of seven younger (275 kg BW) and seven older (490 kg BW) steers. Most steers received three of the six treatments; two extra steers were added to compensate for missing data. Steers had blood vessel catheters and ultrasound flow probes that allowed measurement of net uptake or release of glucose and insulin by portal-drained viscera (PDV), liver, and hindquarters (HQ). Steady-state glucose infusion rate (SSGIR) was intrajugular glucose infused during treatments to maintain euglycemia. Within age groups, Rmax or Rmin and ED50 were estimated by nonlinear regression of glucose flux on arterial plasma insulin concentrations. Steers were killed after sampling, tissues were weighted, and HQ content of fat and protein was determined. Those data were used to predict tissue weights and HQ composition at the time of the euglycemic clamps. Predicted EBW (243 vs 444 kg), liver (4.24 vs 6.19 kg), and HQ (73 vs 122 kg) were heavier for older than for younger steers. Fat in HQ was higher for older than for younger steers (173 vs 134 g/kg), but protein was similar (198 g/kg). The ED50 (mU of insulin/L of plasma) for SSGIR (237 +/- 65 vs 113 +/- 22), liver glucose release (89 +/- 22 vs 44 +/- 11), total glucose entry (418 +/- 184 vs 125 +/- 20), and HQ glucose uptake (488 +/- 151 vs 243 +/- 78) was higher for older than for younger steers. The Rmax (mmol glucose.h-1.kg tissue-1) for SSGIR (2.68 +/- .22 vs 2.09 +/- .23) and HQ (3.08 +/- .33 vs 2.46 +/- .30) was higher for younger than for older steers. Liver glucose release decreased in response to insulin; Rmin (mmol glucose.h-1.kg liver-1) was higher for younger (36.0 +/- 6.9) than for older (24.7 +/- 3.2) steers. We conclude that as steers grew older, heavier, and fatter, their peripheral tissues and liver became less sensitive and less responsive to insulin.}, number={8}, journal={Journal of Animal Science}, author={Eisemann, J. H. and Huntington, G. B. and Catherman, D. R.}, year={1997}, pages={2084–2091} }