@article{britt_2023, title={Randel Lecture: Ensuring a Leading Role for USA Animal Protein in Our World's Food Future}, volume={101}, ISSN={["1525-3163"]}, DOI={10.1093/jas/skad068.065}, abstractNote={Abstract}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Britt, Jack H.}, year={2023}, month={May} }
 @article{marei_de bie_xhonneux_andries_britt_leroy_2022, title={Metabolic and antioxidant status during transition is associated with changes in the granulosa cell transcriptome in the preovulatory follicle in high-producing dairy cows at the time of breeding}, volume={105}, ISSN={["1525-3198"]}, url={https://doi.org/10.3168/jds.2022-21928}, DOI={10.3168/jds.2022-21928}, abstractNote={In this study, we hypothesized that early postpartum (pp) metabolic and oxidative stress conditions in dairy cows (particularly those with severe negative energy balance, NEB) are associated with long-term changes in granulosa cell (GC) functions in the preovulatory follicle at the time of breeding. Blood samples were collected at wk 2 and wk 8 pp from 47 healthy multiparous cows. Follicular fluid (FF) and GC were collected from the preovulatory follicle after estrous synchronization at wk 8. Several metabolic and antioxidant parameters were measured in blood and FF, and their correlations were studied. Subsequently, 27 representative GC samples were selected for RNA sequencing analysis. The GC gene expression data of LH-responsive genes and the estradiol:progesterone ratio in FF were used to identify pre- and post-LH surge cohorts. We compared the transcriptomic profile of subgroups of cows within the highest and lowest quartiles (Q4 vs. Q1) of each parameter, focusing on the pre-LH surge cohort (n = 16, at least 3 in each subgroup). Differentially expressed genes (DEG: adjusted P-value < 0.05, 5% false discovery rate) were determined using DESeq2 analysis and were functionally annotated. Blood and FF β-carotene and vitamin E concentrations at wk 2, but not at wk 8, were associated with the most pronounced transcriptomic differences in the GC, with up to 341 DEG indicative for lower catabolism, increased oxidoreductase activity and signaling cascades that are known to enhance oocyte developmental competence, increased responsiveness to LH, and a higher steroidogenic activity. In contrast, elevated blood NEFA concentrations at wk 2 (and not at wk 8) were associated with a long-term carryover effect detectable in the GC transcriptome at wk 8 (64 DEG). These genes are related to response to lipids and ketones, oxidative stress, and immune responses, which suggests persistent cellular stress and oxidative damage. This effect was more pronounced in cows with antioxidant deficiencies at wk 8 (up to 148 DEG), with more genes involved in oxidative stress-dependent responses, apoptosis, autophagy and catabolic processes, and mitochondrial damage. Interestingly, within the severe NEB cows (high blood NEFA at wk 2), blood antioxidant concentrations (high vs. low) at wk 8 were associated with up to 194 DEG involved in activation of meiosis and other signaling pathways, indicating a better oocyte supportive capacity. This suggests that the cow antioxidant profile at the time of breeding might alleviate, at least in part, the effect of NEB on GC functions. In conclusion, these results provide further evidence that the metabolic and oxidative stress in dairy cows early postpartum can have long-term effects on GC functions in preovulatory follicles at the time of breeding. The interplay between the effects of antioxidants and NEFA illustrated here might be useful to develop intervention strategies to minimize the effect of severe NEB on fertility.}, number={8}, journal={JOURNAL OF DAIRY SCIENCE}, author={Marei, Waleed F. A. and De Bie, Jessie and Xhonneux, Inne and Andries, Silke and Britt, Jack H. and Leroy, Jo L. M. R.}, year={2022}, month={Aug}, pages={6956–6972} }
 @article{britt_cushman_dechow_dobson_humblot_hutjens_jones_mitloehner_ruegg_sheldon_et al._2021, title={Review: Perspective on high-performing dairy cows and herds}, url={https://doi.org/10.1016/j.animal.2021.100298}, DOI={10.1016/j.animal.2021.100298}, abstractNote={Milk and dairy products provide highly sustainable concentrations of essential amino acids and other required nutrients for humans; however, amount of milk currently produced per dairy cow globally is inadequate to meet future needs. Higher performing dairy cows and herds produce more milk with less environmental impact per kg than lower performing cows and herds. In 2018, 15.4% of the world's dairy cows produced 45.4% of the world's dairy cow milk, reflecting the global contribution of high-performing cows and herds. In high-performing herds, genomic evaluations are utilized for multiple trait selection, welfare is monitored by remote sensing, rations are formulated at micronutrient levels, health care is focused on prevention and reproduction is managed with precision. Higher performing herds require more inputs and generate more waste products per cow, thus innovations in environmental management on such farms are essential for lowering environmental impacts. Our focus is to provide perspectives on technologies and practices that contribute most to sustainable production of milk from high-performing dairy cows and herds.}, journal={Animal}, author={Britt, J.H. and Cushman, R.A. and Dechow, C.D. and Dobson, H. and Humblot, P. and Hutjens, M.F. and Jones, G.A. and Mitloehner, F.M. and Ruegg, P.L. and Sheldon, I.M. and et al.}, year={2021}, month={Dec} }
 @article{britt_2019, title={How reproductive management technologies will shape the dairy industry 50 years from now.}, volume={97}, ISSN={["1525-3163"]}, DOI={10.1093/jas/skz122.208}, abstractNote={Abstract}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Britt, Jack H.}, year={2019}, month={Jul}, pages={117–117} }
 @misc{britt_cushman_dechow_dobson_humblot_hutjens_jones_ruegg_sheldon_stevenson_2018, title={Invited review: Learning from the future-A vision for dairy farms and cows in 2067}, volume={101}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2017-14025}, abstractNote={The world's population will reach 10.4 billion in 2067, with 81% residing in Africa or Asia. Arable land available for food production will decrease to 0.15 ha per person. Temperature will increase in tropical and temperate zones, especially in the Northern Hemisphere, and this will push growing seasons and dairy farming away from arid areas and into more northern latitudes. Dairy consumption will increase because it provides essential nutrients more efficiently than many other agricultural systems. Dairy farming will become modernized in developing countries and milk production per cow will increase, doubling in countries with advanced dairying systems. Profitability of dairy farms will be the key to their sustainability. Genetic improvements will include emphasis on the coding genome and associated noncoding epigenome of cattle, and on microbiomes of dairy cattle and farmsteads. Farm sizes will increase and there will be greater lateral integration of housing and management of dairy cattle of different ages and production stages. Integrated sensors, robotics, and automation will replace much of the manual labor on farms. Managing the epigenome and microbiome will become part of routine herd management. Innovations in dairy facilities will improve the health of cows and permit expression of natural behaviors. Herds will be viewed as superorganisms, and studies of herds as observational units will lead to improvements in productivity, health, and well-being of dairy cattle, and improve the agroecology and sustainability of dairy farms. Dairy farmers in 2067 will meet the world's needs for essential nutrients by adopting technologies and practices that provide improved cow health and longevity, profitable dairy farms, and sustainable agriculture.}, number={5}, journal={JOURNAL OF DAIRY SCIENCE}, author={Britt, J. H. and Cushman, R. A. and Dechow, C. D. and Dobson, H. and Humblot, P. and Hutjens, M. F. and Jones, G. A. and Ruegg, P. S. and Sheldon, I. M. and Stevenson, J. S.}, year={2018}, month={May}, pages={3722–3741} }
 @article{stevenson_britt_2017, title={A 100-Year Review: Practical female reproductive management}, volume={100}, ISSN={["1525-3198"]}, DOI={10.3168/jds.2017-12959}, abstractNote={Basic knowledge of mechanisms controlling reproductive processes in mammals was limited in the early 20th century. Discoveries of physiologic processes and mechanisms made early in the last century laid the foundation to develop technologies and programs used today to manage and control reproduction in dairy cattle. Beyond advances made in understanding of gonadotropic support and control of ovarian and uterine functions in basic reproductive biology, advancements made in artificial insemination (AI) and genetics facilitated rapid genetic progress of economically important traits in dairy cattle. Technologies associated with management have each contributed to the evolution of reproductive management, including (1) hormones to induce estrus and ovulation to facilitate AI programs; (2) pregnancy diagnosis via ultrasonography or by measuring conceptus-derived pregnancy-associated glycoproteins; (3) estrus-detection aids first devised for monitoring only physical activity but that now also quantitate feeding, resting, and rumination times, and ear temperature; (4) sex-sorted semen; (5) computers and computerized record software packages; (6) handheld devices for tracking cow location and retrieving cow records; and (7) genomics for increasing genetic progress of reproductive and other economically important traits. Because of genetic progress in milk yield and component traits, the dairy population in the United States has been stable since the mid 1990s, with approximately 9 to 9.5 million cows. Therefore, many of these technologies and changes in management have been developed in the face of increasing herd size (4-fold since 1990), and changes from pastoral or dry-lot dairies to increased housing of cows in confinement buildings with freestalls and feed-line lockups. Management of groups of "like" cows has become equally important as management of the one. Management teams, including owner-managers, herdsmen, AI representatives, milkers, and numerous consultants dealing with health, feeding, and facilities, became essential to develop working protocols, monitor training and day-to-day chores, and evaluate current trends and revenues. Good management teams inspect and follow through with what is routinely expected of workers. As herd size will undoubtedly increase in the future, practical reproductive management must evolve to adapt to the new technologies that may find more herds being milked robotically and applying technologies not yet conceived or introduced.}, number={12}, journal={JOURNAL OF DAIRY SCIENCE}, author={Stevenson, J. S. and Britt, J. H.}, year={2017}, month={Dec}, pages={10292–10313} }
 @misc{leroy_valckx_jordaens_de bie_desmet_van hoeck_britt_marei_bols_2015, title={Nutrition and maternal metabolic health in relation to oocyte and embryo quality: critical views on what we learned from the dairy cow model}, volume={27}, ISSN={["1448-5990"]}, DOI={10.1071/rd14363}, abstractNote={Although fragmented and sometimes inconsistent, the proof of a vital link between the importance of the physiological status of the mother and her subsequent reproductive success is building up. High-yielding dairy cows are suffering from a substantial decline in fertility outcome over past decades. For many years, this decrease in reproductive output has correctly been considered multifactorial, with factors including farm management, feed ratios, breed and genetics and, last, but not least, ever-rising milk production. Because the problem is complex and requires a multidisciplinary approach, it is hard to formulate straightforward conclusions leading to improvements on the ‘work floor’. However, based on remarkable similarities on the preimplantation reproductive side between cattle and humans, there is a growing tendency to consider the dairy cow’s negative energy balance and accompanying fat mobilisation as an interesting model to study the impact of maternal metabolic disorders on human fertility and, more specifically, on oocyte and preimplantation embryo quality. Considering the mutual interest of human and animal scientists studying common reproductive problems, this review has several aims. First, we briefly introduce the ‘dairy cow case’ by describing the state of the art of research into metabolic imbalances and their possible effects on dairy cow reproduction. Second, we try to define relevant in vitro models that can clarify certain mechanisms by which aberrant metabolite levels may influence embryonic health. We report on recent advances in the assessment of embryo metabolism and meantime critically elaborate on advantages and major limitations of in vitro models used so far. Finally, we discuss hurdles to be overcome to successfully translate the scientific data to the field.}, number={4}, journal={REPRODUCTION FERTILITY AND DEVELOPMENT}, author={Leroy, Jo L. M. R. and Valckx, Sara D. M. and Jordaens, Lies and De Bie, Jessie and Desmet, Karolien L. J. and Van Hoeck, Veerle and Britt, Jack H. and Marei, Waleed F. and Bols, Peter E. J.}, year={2015}, pages={693–703} }
 @misc{britt_aberle_esbenshade_males_2008, title={INVITED REVIEW: Animal science departments of the future}, volume={86}, ISSN={["0021-8812"]}, DOI={10.2527/jas.2008-1015}, abstractNote={Departments of animal science were established in agricultural colleges of public universities just over 100 yr ago, shortly before the founding of today's American Society of Animal Science. These departments and colleges have been remarkably resilient, changing little structurally. Yet, the future portends significant changes in these departments and colleges in response to shifts in how public higher education is financed and how society views the roles of animals in providing food and companionship. Funding for public higher education will continue to decline as a percentage of government appropriations. Public universities will garner more funding from gifts, endowments, grants, contracts, and tuition but will be held more accountable than today by public officials. Departments of animal science will retain strong constituencies and will be major units of most agricultural colleges; however, their students and faculty will be more diverse. Departments of animal science will focus on more species of animals and on a greater role of animals in society. Disciplines of faculty members in departments of animal science will become broader, and research projects will be more complex and have longer horizons, ultimately focused more on sustainability. Departments will share more resources across state and national boundaries, and there will be less duplication of effort regionally. Departments of animal science will continue to be important academic units of universities into the 22nd century.}, number={11}, journal={JOURNAL OF ANIMAL SCIENCE}, author={Britt, J. H. and Aberle, E. D. and Esbenshade, K. L. and Males, J. R.}, year={2008}, month={Nov}, pages={3235–3244} }
 @article{cushman_desouza_hedgpeth_britt_2001, title={Alteration of activation, growth, and atresia of bovine preantral follicles by long-term treatment of cows with estradiol and recombinant bovine somatotropin}, volume={65}, ISSN={["0006-3363"]}, DOI={10.1095/biolreprod65.2.581}, abstractNote={Abstract The hypothesis was that long-term treatment of cattle with estradiol (E2) and bovine somatotropin (bST) would alter the earliest stages of folliculogenesis. Nonlactating Holstein cows (n = 26) were treated in a 2 × 2 arrangement with E2 (2 × 24 mg implants, 67.1 ± 1.4 days) and bST (Posilac, 63.6 ± 1.5 days). At Day 67 ± 1.3, one ovary was removed for morphometric and immunohistochemical analysis. For each ovary, 388 ± 38 microscopic fields (2 × 2 mm) were examined and follicles within each field were classified by histological stage. Fields that contained no follicles were classified as empty. Empty fields (n = 100 per ovary) were further classified as containing no evidence of follicles or containing atretic remnants of follicles. Approximately 30 4-μm sections per ovary were stained for proliferating cell nuclear antigen (PCNA), and 150 fields per ovary were evaluated. Additional sections (n = 10 per ovary) were assessed immunohistochemically for apoptosis, and fluorescence intensity was determined for each follicle. Treatment with bST significantly decreased percentage of empty fields containing atretic remnants. Treatment with E2 induced activation of follicles as shown by a decrease in percentage of primordial follicles and an increase in percentage of primary follicles as determined by PCNA staining. At the primary follicle stage the combination of bST + E2 decreased apoptosis as shown by decreased fluorescence intensity. Thus, E2 induced activation of follicles, bST enhanced survival, and the combination lowered atresia.}, number={2}, journal={BIOLOGY OF REPRODUCTION}, author={Cushman, RA and DeSouza, JC and Hedgpeth, VS and Britt, JH}, year={2001}, month={Aug}, pages={581–586} }
 @article{cushman_desouza_hedgpeth_britt_2001, title={Effect of long-term treatment with recombinant bovine somatotropin and estradiol on hormone concentrations and ovulatory response of superovulated cattle}, volume={55}, ISSN={["0093-691X"]}, DOI={10.1016/S0093-691X(01)00500-3}, abstractNote={The objective was to assess effects of long-term treatment with recombinant bovine somatotropin (bST) and estradiol-17β (E2) on the number of follicles that ovulated in response to FSH. Non-lactating Holstein and Jersey cows (Trial 1, n=27) and Angus cows and heifers (Trial 2, n=35) received two ear implants of E2 and biweekly injections of bST in a 2 × 2 arrangement of treatments. Estradiol implants were removed 74.6 ± 1.1 d after insertion and 18.1 ± 0.9 d after the last biweekly injection of bST. Cows were stimulated with FSH-P beginning 2 d after removal of E2 implants, and PGF2alpha (PGF) was given on the third day of FSH treatment Ovaries were collected to determine the number of CL at 1 to 2 wk after treatment with PGF. In Trial 2 only, cattle were inseminated at estrus and embryos were collected 6 to 8 d later. Implants of E2 increased (P < 0.01) serum E2 8-fold initially and E2 was still elevated 5-fold at removal of implants. Injections of bST increased (P < 0.01) serum growth hormone (GH) 15-fold and insulin-like growth factor-I (IGF-I) 3-fold. In Trial 1, number of CL was increased by the combination of bST+E2 (P < 0.01). In Trial 2, E2 increased the number of CL (P < 0.05), and bST increased the number of total ova and transferable embryos (P < 0.01). We conclude that long-term treatment with bST and E2 may interact to enhance follicular development and ovulatory response to FSH.}, number={7}, journal={THERIOGENOLOGY}, author={Cushman, RA and DeSouza, JC and Hedgpeth, VS and Britt, JH}, year={2001}, month={Apr}, pages={1533–1547} }
 @article{cavalieri_farin_kinder_van camp_whitacre_washburn_britt_2001, title={Ovarian follicular development following administration of progesterone or aspiration of ovarian follicles in Holstein cows}, volume={55}, ISSN={["1879-3231"]}, DOI={10.1016/S0093-691X(01)00445-9}, abstractNote={The objective of this study was to compare the effects of administration of a single injection of progesterone (P4) and follicle aspiration on Day 7 of the estrous cycle on the timing and synchrony of follicular wave emergence, time of ovulation, and concentrations of P4, estradiol and FSH in Holstein cows. Twenty cows were assigned to 4 groups (n=5 cows per group) in a 2 by 2 factorial arrangement. Cows were treated on Day 7 (Day 0 = estrus) of the estrous cycle with either sham follicular aspiration and an oil vehicle administered intramuscularly (control), aspiration of ovarian follicles (aspiration), 200 mg of P4 im, or aspiration and 200 mg of P4 im (aspiration + P4). On Day 11, PGF(2alpha)(25mg) was administered to all groups. Synchrony of ovulation was less variable in each of the treatment groups compared with the control group (P<0.05), whereas ovulation was delayed in cows in the P4 group (P<0.05). Day of follicular wave emergence was delayed in the cows of the P4 group compared with cows in the aspiration and aspiration + P4 groups (P<0.01), whereas variability in wave emergence was less among both groups of aspirated cows compared with the cows in the control group (P<0.01). More follicles 4 to 7 mm in diameter were detected in the 2 aspiration groups compared with the cows in the control and P4 group (P<0.05). No difference was detected among groups in the maximum concentration of FSH associated with follicular wave emergence. We conclude that both the administration of P4 and the aspiration of follicles on Day 7 of the estrous cycle improves the synchrony of ovulation when luteolysis is induced on Day 11 and results in similar concentrations of FSH at the time of follicular wave emergence, but the timing of wave emergence and the number of follicles post-emergence differ.}, number={3}, journal={THERIOGENOLOGY}, author={Cavalieri, J and Farin, PW and Kinder, JE and Van Camp, SD and Whitacre, MD and Washburn, SP and Britt, JH}, year={2001}, month={Feb}, pages={805–821} }
 @article{sinclair_squires_raeside_britt_hedgpeth_2001, title={The effect of early postnatal treatment with a gonadotropin-releasing hormone agonist on the developmental profiles of testicular steroid hormones in the intact male pig}, volume={79}, DOI={10.2527/2001.7941003x}, abstractNote={Three studies examined the effects of early postnatal treatment with a GnRH agonist on plasma concentrations of testosterone, dehydroepian-drosterone sulfate, 16-androstene steroids in fat and salivary glands, androstenone in fat and plasma, and testicular development of intact male pigs. The first study involved 45 7-d-old pigs assigned to three treatment groups: 1) boars administered 100 microg/kg of Lupron depot, 2) boars administered 200 microg/kg of Lupron depot, and 3) control boars receiving a saline carrier. The second study involved 20 7-d-old pigs assigned to two treatments: daily injection of 200 microL of 0.5 mg/mL Lupron from d 7 to 35 and controls treated with saline. The third study involved a total of 100 animals assigned to 10 groups of 10 based on their age at slaughter. These groups were subdivided into one of two treatments: 1) boars injected with 200 microL of 0.5 mg/mL of Lupron from d 3 to 35 and 2) control boars injected with saline. Testicular steroid hormone concentrations in plasma decreased (P < 0.01) within 7 d of GnRH agonist treatment. Following cessation of treatment, steroid levels increased to control levels and remained constant until the final rise at 5 mo. Plasma testosterone levels in the 100 microg/kg depot treatment group were higher (P < 0.05) than that of the 200 microg/kg and control group at 164 d of age. There were no differences between treatments (P > 0.05) in testicular steroid hormone levels at the end of study 2 or 3. There were no differences (P > 0.05) in concentrations of 16-androstene steroids in salivary glands between any of the treatment groups at market weight in studies 1 and 2. Fat androstenone levels measured in the third study ranged between 0.6 microg/g and 4.2 microg/g at 7 to 28 d of age. Treatment with GnRH agonist decreased plasma steroid levels and testicular development; however, by d 60 testicular size and weight were at control levels and remained similar until 180 d of age. The results of these studies indicate that daily administration of a GnRH agonist significantly decreased testicular development and steroidogenesis only during treatment, but testis growth and steroidogenesis had returned to control levels by 60 d of age in male pigs. Suppression of the early postnatal rise in testicular steroid hormones did not affect growth performance or steroid hormone levels at 5 to 6 mo of age.}, number={4}, journal={Journal of Animal Science}, author={Sinclair, P. A. and Squires, E. J. and Raeside, J. I. and Britt, Jack and Hedgpeth, V. G.}, year={2001}, pages={1003–1010} }
 @article{cushman_hedgpeth_echternkamp_britt_2000, title={Evaluation of numbers of microscopic and macroscopic follicles in cattle selected for twinning}, volume={78}, DOI={10.2527/2000.7861564x}, abstractNote={We hypothesized that the number of microscopic follicles present in the ovaries of cattle selected for twin births (Twinner) would be greater than in the ovaries of contemporary Controls. Ovaries were collected from seven Control and seven Twinner cows at slaughter. The number of Small (1 to 3.9 mm), Medium (4 to 7.9), and Large (> 8 mm) surface follicles was counted and one ovary was fixed for histological evaluation. Fifty to sixty consecutive 6-microm slices were taken from a piece of cortical tissue, approximately 1 cm x 1 cm in area, located between the surface follicles. Microscopic follicles were classified as primordial (oocyte surrounded by a single layer of squamous pregranulosa cells), primary (oocyte surrounded by a single layer of one or more cuboidal granulosa cells), secondary (oocyte surrounded by two or more layers of granulosa cells), or tertiary (oocyte surrounded by multiple layers of granulosa cells with initiation of antrum formation to < or = 1 mm in diameter). The total number of follicles was counted in 200 fields (2 mm x 2 mm) per ovary. A field containing no follicles was classified as empty. There were significantly more secondary follicles in Twinner compared with Control ovaries (12.9 vs 6.3; P < .05). Twinners also tended to have more small surface follicles (35.4 vs 49.0; P < 0.1). We conclude that ovaries of Control and Twinner cows do not differ in the number of primordial follicles or in the number of follicles activated into the growing pool; however, Twinner cows are able to maintain more growing follicles at the secondary and subsequent stages of development.}, number={6}, journal={Journal of Animal Science}, author={Cushman, R. A. and Hedgpeth, V. S. and Echternkamp, S. E. and Britt, Jack}, year={2000}, pages={1564–1567} }
 @article{shaw_britt_2000, title={In vivo oxytocin release from microdialyzed bovine corpora lutea during spontaneous and prostaglandin-induced regression}, volume={62}, ISSN={["0006-3363"]}, DOI={10.1095/biolreprod62.3.726}, abstractNote={Abstract The release of luteal oxytocin during spontaneous and prostaglandin-induced luteolysis was investigated in cows. A continuous-flow microdialysis system was used in 11 cows to collect dialysates of the luteal extracellular space between Days 12 and 24 postestrus. Seven cows were untreated and were expected to exhibit spontaneous luteolysis during sampling, whereas 4 cows received prostaglandin F2α (PGF2α) systemically between Days 13 and 15 to induce luteolysis during sampling. Oxytocin was detectable in the dialysate of all cows before Day 16 postestrus and occurred as 2 or 3 discrete pulses per 12-h sampling period. For non-PGF2α-treated cows, dialysate oxytocin content began to decline spontaneously on Day 15 postestrus and was undetectable by Day 17 postestrus. Oxytocin decay curves preceded onset of serum progesterone decline by at least 72 h and were not related temporally with onset of progesterone decline within cow. Exogenous PGF2α (25 mg, i.m.) produced a 10-fold increase in dialysate oxytocin within 1 h (1.9 ± 0.3 pg/ml to 20.8 ± 3.0 pg/ml; P < 0.01). Dialysate oxytocin then declined to pretreatment concentrations within 2 h and was undetectable within 8 h posttreatment. A second PGF2α injection given 20 h after the first did not result in a measurable increase in dialysate oxytocin, probably because luteolysis was underway. Although robust luteal oxytocin release was observed after treatment with a pharmacological dose of PGF2α, the lack of detectable oxytocin secretion during spontaneous luteolysis suggests that the contribution of luteal oxytocin in the cow may be less than that proposed for the ewe.}, number={3}, journal={BIOLOGY OF REPRODUCTION}, author={Shaw, DW and Britt, JH}, year={2000}, month={Mar}, pages={726–730} }
 @article{whaley_hedgpeth_farin_martus_jayes_britt_2000, title={Influence of vitamin A injection before mating on oocyte development, follicular hormones, and ovulation in gilts fed high-energy diets}, volume={78}, DOI={10.2527/2000.7861598x}, abstractNote={Previous research revealed that treatment with vitamin A approximately 5 d before ovulation may increase litter size in weaned sows and improve embryonal survival in gilts fed high-energy diets that reduced embryonal survival. For the current study, the hypothesis was that administration of vitamin A before ovulation would alter development of follicles and oocytes in a way favorable to enhanced embryonal survival. (Landrace x Large White) x (Duroc x Hampshire) gilts (n = 44) were fed 11.0 Mcal ME x gilt(-1) x d(-1) beginning 7 d after second estrus and given (i.m.) corn oil or 1 x 10(6) IU of vitamin A (retinyl palmitate) on d 15 after second estrus. Gilts were checked for estrus every 4 h, mated naturally at third estrus, and assigned randomly to undergo midventral laparotomy beginning at 24 to 28, 28 to 32, 32 to 36, or 36 to 40 h after onset of third estrus. At laparotomy, ovulated oocytes and early-stage embryos were recovered from oviducts, and ovaries were removed for aspiration of oocytes and granulosa cells from unovulated follicles. Oocytes and embryos were stained for assessment of stage of development. Granulosa cells were cultured to assess their ability to secrete progesterone. Follicular fluid was assayed for progesterone, estradiol-17beta, IGF-I, and PGF2alpha. Treatment with vitamin A altered development of oocytes and embryos by decreasing the percentage at the germinal vesicle stage and increasing the percentage at advanced stages. Mean stage of development was increased by vitamin A, but variation in stage was decreased. Among follicles matched by meiotic stage of oocyte, follicular fluid concentrations of progesterone, IGF-I, and PGF2alpha were greater in vitamin A-treated gilts than in controls, but treatment with vitamin A in vivo did not affect LH-stimulated or unstimulated secretion of progesterone by granulosa cells in vitro. These data provide evidence that vitamin A may influence embryonic development by advancing resumption of meiosis and altering follicular hormonal environment during follicle maturation.}, number={6}, journal={Journal of Animal Science}, author={Whaley, S. L. and Hedgpeth, V. S. and Farin, C. E. and Martus, N. S. and Jayes, F. C. L. and Britt, Jack}, year={2000}, pages={1598–1607} }
 @article{armstrong_flowers_britt_1999, title={Control of the weaning-to-estrus interval in sows using gonadotropins and prostaglandins during lactation}, volume={77}, DOI={10.2527/1999.7792533x}, abstractNote={Two experiments were conducted to examine the effectiveness of various strategies using gonadotropins to induce ovulation during lactation as a means of controlling the weaning-to-estrus interval in sows. The objective of Exp. 1 was to examine the efficacy of various gonadotropin regimens for induction of ovulation during lactation. Primiparous (n = 60) and multiparous (n = 83) crossbred sows were assigned, before farrowing, to one of four treatments: no injection (control); 1,000 IU hCG on d 0 (hCG-0; d 0 = day of farrowing); P.G. 600 + 1,000 IU hCG 4 and 7 d after farrowing, respectively (hCG-7); or P.G. 600 + 1,000 IU hCG 11 and 14 d after farrowing, respectively (hCG-14). Sows were weaned on 18 +/- 2 d after farrowing and monitored daily for estrus via exposure to mature boars. The criterion for determining the induction of ovulation was a sustained increase in serum progesterone concentrations above 4.0 ng/mL. The most consistent response to exogenous gonadotropins was on d 0, with an 80% response in primiparous sows (12/15) and a 71% response in multiparous sows (15/21). Weaning-to-estrus intervals for multiparous sows were longer (P = .05) for hCG-14 and hCG-7 than for control and hCG-0 sows. Weaning-to-estrus intervals for primiparous sows were longer (P = .05) for the hCG-14 than for the hCG-0 treatment. The objective of Exp. 2 was to ascertain the effects of postpartum treatment with hCG (1,000 IU) on d 0 and PGF2alpha (10 mg) at d 14 on the weaning-to-estrus interval in multiparous sows weaned at d 14 after birth. Before farrowing, sows (n = 60) were randomly assigned to one of four treatments: positive control, weaning at d 21; negative control, weaning at d 14; hCG within 24 h after farrowing, weaning at d 14; or hCG within 24 h after farrowing and PGF2alpha at weaning, weaning at d 14. Weaning-to-estrus intervals were longer (P = .05) in sows receiving PGF2alpha than in the other treatments. Results indicate that it is possible to induce ovulation immediately after farrowing, using a single injection of hCG, and this strategy can be used to uncouple weaning from the resumption of reproductive activity. However, the administration of PGF2alpha at 14 d after farrowing did not consistently cause regression of the induced corpora lutea.}, number={9}, journal={Journal of Animal Science}, author={Armstrong, T. A. and Flowers, W. L. and Britt, Jack}, year={1999}, pages={2533–2539} }
 @article{swanchara_armstrong_britt_1999, title={Effects of active immunization against growth-hormone releasing factor on puberty and reproductive development in gilts}, volume={77}, DOI={10.2527/1999.7771807x}, abstractNote={Hormones within the somatotropin cascade influence several physiological traits, including growth and reproduction. Active immunization against growth hormone-releasing factor (GRFi) initiated at 3 or 6 mo of age decreased weight gain, increased deposition of fat, and delayed puberty in heifers. Two experiments were conducted to investigate the effects of GRFi on puberty and subsequent ovulation rate in gilts. Crossbred gilts were actively immunized against GRF-(1-29)-(Gly)2-Cys-NH2 conjugated to human serum albumin (GRFi) or against human serum albumin alone (HSAi). In Exp. 1, gilts were immunized against GRF (n = 12) or HSA (n = 12) at 92 +/- 1 d of age. At 191 d of age, antibody titers against GRF were greater (P < .05) in GRFi (55.5 +/- 1.3%) than in HSAi (.4 +/- 2%) gilts. The GRFi decreased (P < .05) BW (86 +/- 3 vs 104 +/- 3 kg) by 181 d of age and increased (P < .05) backfat depth (15.7 +/- .4 vs 14.8 +/- .4 mm) by 130 d of age. At 181 d of age, GRFi reduced the frequency of ST release (1.0 +/- .5 vs 5.0 +/- .5, peaks/24 h; P < .0001) and decreased (P < .01) ST (1.1 +/- .06 vs 1.7 +/- .06 ng/mL), IGF-I (29 +/- 2 vs 107 +/- 2 ng/mL), and insulin concentrations (3.5 +/- .2 vs 6.3 +/- .2 ng/mL). The GRFi decreased (P < .05) feed conversion efficiency but did not alter age at puberty (GRFi = 199 +/- 5 d vs HSAi = 202 +/- 5 d) or ovulation rate after second estrus (GRFi = 10.7 +/- .4 vs HSAi = 11.8 +/- .5). In Exp. 2, gilts were immunized against GRF (n = 35) or HSA (n = 35) at 35 +/- 1 d of age. The GRFi at 35 d of age did not alter the number of surface follicles or uterine weight between 93 and 102 d of age, but GRFi decreased (P < .05) ovarian weight (.41 +/- .08 vs 1.58 +/- .4 g) and uterine length (17.2 +/- 1.1 vs 25.3 +/- 2.3 cm). Immunization against GRF reduced (P < .05) serum IGF-I (GRFi = 50 +/- 4 vs HSAi = 137 +/- 4 ng/mL) and BW (GRFi = 71 +/- 3 vs HSAi = 105 +/- 3 kg) and increased (P < .05) backfat depth (GRFi = .38 +/- .03 vs HSAi = .25 +/- .02 mm/kg). Age at puberty was similar in GRFi and HSAi gilts, but ovulation rate was lower (P < .05) after third estrus in GRFi (11.3 +/- .8) than in HSAi (13.8 +/- .8) gilts. Thus, GRFi at 92 or 35 d of age decreased serum ST, IGF-I, and BW in prepubertal gilts without altering age of puberty. However, GRFi at 35 d of age, but not 92 d of age, decreased ovulation rate. These results indicate that alterations in the somatotropic axis at 1 mo of age can influence reproductive development in pubertal gilts.}, number={7}, journal={Journal of Animal Science}, author={Swanchara, K. W. and Armstrong, J. D. and Britt, Jack}, year={1999}, pages={1807–1814} }
 @article{farin_slenning_britt_1999, title={Estimates of pregnancy outcomes based on selection of bovine embryos produced in vivo or in vitro}, volume={52}, ISSN={["0093-691X"]}, DOI={10.1016/S0093-691X(99)00160-0}, abstractNote={The objective of this study was to estimate the degree of variation among experienced evaluators selecting in vivo- or in vitro-produced embryos for transfer and to determine how this affects both the proportion of recipients becoming pregnant after transfer, and the number of embryo transfers required per pregnancy. Data from 6 experienced evaluators who graded Day 7 embryos produced either in vivo (n = 15) or in vitro (n = 15) were used to estimate these effects. The evaluators viewed video recorded images of the embryos and classified each embryo for stage of development and quality grade (1 = excellent, 2 = good, 3 = fair, 4 = degenerated and nontransferable). The statistical model considered transfer of embryos of the following individual or combined grades: Grade 1 only, Grade 2 only, Grade 3 only, Grades 1 and 2, Grades 2 and 3, and Grades 1, 2 and 3. Probabilities of pregnancy after embryo transfer were based on pregnancy rates of recipients at the facility of 1 of the 6 evaluators where the percentages of heifers pregnant after the transfer of Grade 1, 2 and 3 embryos, by embryo source, were 76, 65 and 54% (in vivo), and 59, 45 and 30% (in vitro). Within most grades, the proportion of embryos selected for transfer differed (P < 0.05) among the 6 evaluators. Although no significant differences (P > 0.10) were found among evaluators in the proportion of recipients pregnant after transfer within any embryo grade, there was substantial variation among evaluators in the proportion of recipients becoming pregnant, especially for embryos produced in vitro. Estimated percentages of heifers becoming pregnant for embryos classified as Grade 1, 2 or 3 were 66 to 76, 62 to 69, and 54 to 60%, respectively, for in vivo-produced embryos; and, 39 to 59, 15 to 45, and 24 to 32%, respectively, for in vitro-produced embryos. Approximately twice as many transfers were needed per pregnancy for embryos produced in vitro as for those produced in vivo regardless of the grade.}, number={4}, journal={THERIOGENOLOGY}, author={Farin, PW and Slenning, BD and Britt, JH}, year={1999}, month={Sep}, pages={659–670} }
 @article{cushman_desouza_hedgpeth_britt_1999, title={Superovulatory response of one ovary is related to the micro- and macroscopic population of follicles in the contralateral ovary of the cow}, volume={60}, ISSN={["1529-7268"]}, DOI={10.1095/biolreprod60.2.349}, abstractNote={We hypothesized that the ovulatory response of one ovary to FSH would be related positively to the size of the primordial and growing pools of follicles in the other ovary. Nonlactating cows (n = 26) were unilaterally ovariectomized and 2 days later were superovulated. The superovulatory response was classified as Low (< 5 corpora lutea [CL]), Medium (5-14 CL), or High (> 14 CL). Surface follicles on the ovary removed before superovulation were classified as small (1-3 mm), medium (3-7 mm), or large ( > 7 mm), and the ovary was then fixed and serially sectioned. Follicles </= 1 mm in diameter in 388 +/- 38 fields (2 x 2 mm) per cow were classified as primordial, primary, secondary, or tertiary. By classification, Suboptimal ovaries contained < 100 follicles </= 1 mm and Optimal ovaries contained > 250 follicles </= 1 mm. Number of CL was correlated positively with total number of primordial, tertiary, and medium surface follicles. Number of Empty fields (2 x 2-mm fields containing no follicles) was correlated negatively with superovulatory response and number of primordial follicles. Number of CL was related to number of tertiary follicles in a positive linear manner and the number of medium follicles in a positive quadratic manner (r 2 = 0.66). Numbers of primordial, tertiary, small surface follicles, medium surface follicles, and total surface follicles were lower (p </= 0.06) in the Low superovulatory response group than in the Medium or High group. Suboptimal ovaries had fewer small surface follicles and fewer CL than Optimal ovaries (p < 0.05). We conclude that superovulatory response in cattle is related positively to the pools of primordial and growing follicles in the bovine ovary.}, number={2}, journal={BIOLOGY OF REPRODUCTION}, author={Cushman, RA and DeSouza, JC and Hedgpeth, VS and Britt, JH}, year={1999}, month={Feb}, pages={349–354} }
 @article{cushman_davis_boonyaprakob_hedgpeth_burns_britt_1999, title={Technical note: Use of slow-release estradiol and prostaglandin F-2 alpha to induce pseudopregnancy and control estrus in gilts}, volume={77}, DOI={10.2527/1999.77112883x}, abstractNote={We determined whether a single injection of slow-release estradiol-17beta (SRE2) would induce pseudopregnancy in gilts and whether PGF2alpha would regress the corpora lutea (CL) of pseudopregnancy. Crossbred gilts (n = 40) were induced to ovulate by treatment with 400 IU of hCG + 200 IU of eCG (PG600, Intervet, Millsboro, DE) given at 180 d of age (d = 0). On d 14, gilts were injected i.m. with one of five doses (n = 8 gilts/dose) of SRE2 (0, 12.5, 25, 50, or 100 mg). Blood samples were collected before SRE2 and twice weekly until d 73 to monitor serum progesterone (P4) and estradiol (E2). On d 59, gilts received (i.m.) 10 mg of PGF2alpha (Lutalyse, Pharmacia Upjohn, Kalamazoo, MI) and were checked for estrus for 7 d. On d 62, mammary development was scored (0 = no development; 1 = some development; 2 = teat and gland development) by a neutral observer. Treatment with SRE2 increased (P < .05) peak E2 concentrations, duration of luteal function, and mammary gland score. There were no differences (chi-square, P > .05) among doses of SRE2 in the percentage of pseudopregnant gilts that showed luteolysis after PGF2alpha. We conclude that a single injection of SRE2 can induce pseudopregnancy and that the CL can be regressed with PGF2alpha, providing a simple method for controlling estrus in gilts.}, number={11}, journal={Journal of Animal Science}, author={Cushman, R. A. and Davis, P. E. and Boonyaprakob, U. and Hedgpeth, V. S. and Burns, P. J. and Britt, Jack}, year={1999}, pages={2883–2885} }
 @article{britt_cushman_hedgpeth_shaw_1999, title={Use of an ovarian biopsy to predict surface follicle numbers on the bovine ovary.}, volume={60}, number={1999}, journal={Biology of Reproduction}, author={Britt, J. H. and Cushman, R. A. and Hedgpeth, V. S. and Shaw, D. W.}, year={1999}, pages={107} }
 @article{whaley_hedgpeth_britt_1997, title={Evidence that injection of vitamin A before mating may improve embryo survival in gilts fed normal or high-energy diets}, volume={75}, DOI={10.2527/1997.7541071x}, abstractNote={The hypothesis was that administration of vitamin A before ovulation would improve embryo survival in gilts fed a high-energy diet intentionally to reduce embryo survival. Forty crossbred ([Landrace x Large White] x [Duroc x Hampshire]) gilts were fed control (5.5 Mcal ME/d) or high-energy (11.0 Mcal ME/d) diets from 7 d after second estrus until 11 to 12 d after third estrus. Gilts in each dietary group received (i.m.) corn oil or retinyl palmitate (1 x 10(6) IU, vitamin A) on d 15 after second estrus and were mated at third estrus. Blood for determination of progesterone and estradiol was collected twice daily. The uterus and ovaries were removed on d 11 or 12 after third estrus for assessment of number of CL, and number, size and aromatase activity of embryos. Neither diet nor vitamin treatment affected number of CL. The high-energy diet exerted a negative effect on number of embryos (P = .09) and embryo survival (P = .07), whereas vitamin A exerted a positive effect on number of embryos (P = .07) and embryo survival (P = .08). The high-energy diet increased variation in embryo diameter, whereas vitamin A reduced variation in diameter and increased average diameter. Neither diet nor vitamin treatment influenced aromatase activity of embryos. Diet and vitamin treatment interacted with day to influence serum progesterone, but not estradiol. Injecting vitamin A before estrus restored embryo survival to normal levels in gilts fed high-energy diets, and this may be attributable to decreased variation in size of embryos.}, number={4}, journal={Journal of Animal Science}, author={Whaley, S. L. and Hedgpeth, V. S. and Britt, Jack}, year={1997}, pages={1071–1077} }
 @article{jayes_britt_esbenshade_1997, title={Role of gonadotropin-releasing hormone pulse frequency in differential regulation of gonadotropins in the gilt}, volume={56}, ISSN={["1529-7268"]}, DOI={10.1095/biolreprod56.4.1012}, abstractNote={We tested the hypothesis that different GnRH pulse frequencies will affect serum LH and FSH differently. Ovariectomized gilts (n = 6), immunized against GnRH, were given 200-ng pulses of GnRH agonist (GnRH-A) every 180 min for 3 days (pretreatment), followed by GnRH-A pulses every 30, 60, or 180 min for 3 days (treatment) in a Latin rectangle design. Mean gonadotropin concentrations did not change over time when GnRH pulses were administered every 180 min. Initiation of high GnRH-A pulse frequency (30 min) caused a robust increase in serum LH to 265% of the pretreatment level (p < or = 0.007) and a more moderate increase in serum FSH to 127% of pretreatment level (p < or = 0.02). After 66 h of frequent pulsing, desensitization had occurred and serum LH concentrations were similar to pretreatment concentrations, but serum FSH had decreased to 53% of pretreatment levels (p < or = 0.0008). After 72 h of treatment, 5 micrograms GnRH-A was infused to estimate residual releasable pools of LH and FSH, and the amounts of LH and FSH released were negatively correlated with GnRH-A pulse frequency. The results of this study imply that the LH surge is terminated because the pituitary gland becomes incapable of responding to an otherwise adequate stimulus, and not because of exhaustion of releasable LH pools. Our results confirm that in the pig the response to altered GnRH-A pulse frequency differs between LH and FSH. High GnRH pulse frequency is more effective in acutely releasing LH than FSH. Low pulse frequency of GnRH supports FSH synthesis and release, but is not as effective in increasing LH concentrations, while high GnRH pulse frequency inhibits FSH synthesis and release.}, number={4}, journal={BIOLOGY OF REPRODUCTION}, author={Jayes, FCL and Britt, JH and Esbenshade, KL}, year={1997}, month={Apr}, pages={1012–1019} }
 @article{britt_1995, title={An update on current concepts of reproductive physiology and endocrinology}, volume={3}, number={1}, journal={Cattle Practice}, author={Britt, J. H.}, year={1995}, pages={71} }
 @article{britt_1995, title={Relationships between postpartum nutrition, weight loss and fertility}, volume={3}, number={1}, journal={Cattle Practice}, author={Britt, J. H.}, year={1995}, pages={79} }
 @article{britt_1995, title={The relationship between postpartum estrous cycles, estrus cycle length, and early embryonic death}, volume={3}, number={1}, journal={Cattle Practice}, author={Britt, J. H.}, year={1995}, pages={85} }
 @article{britt_sesti_1991, title={Maximizing fertility and fecundity in the sow}, number={3}, journal={Revista Brasileira de Reproducao Animal}, author={Britt, J. H. and Sesti, L. A. C.}, year={1991}, pages={22} }
 @article{britt_esbenshade_ziecik_1991, title={ROLES OF ESTRADIOL AND GONADOTROPIN-RELEASING-HORMONE IN CONTROLLING NEGATIVE AND POSITIVE FEEDBACK ASSOCIATED WITH THE LUTEINIZING-HORMONE SURGE IN OVARIECTOMIZED PIGS}, volume={45}, ISSN={["0006-3363"]}, DOI={10.1095/biolreprod45.3.478}, abstractNote={Ovariectomized gilts (n = 63) were given estradiol benzoate (estradiol), antiserum to neutralize endogenous GnRH, and pulses of a GnRH agonist (GnRH-A) to stimulate release of LH. GnRH-A was given as 200-ng pulses hourly from 0 to 54 h and as 100- or 200-ng pulses every 30 or 60 min from 54 to 96 h after estradiol. Estradiol alone suppressed LH from 6 to 54 h and elicited an LH surge that peaked at 72 h. When GnRH-A was given every 30-60 min from 0 to 96 h, estradiol suppressed LH for 6-12 h, but then LH returned to pre-estradiol concentrations. When pulses of GnRH-A were given only between 54 and 96 h after estradiol, the surge of LH was related positively to dose and frequency of GnRH-A. We conclude that 1) estrogen acts at the hypothalamus to inhibit release of GnRH for 54 h and then causes a synchronous release of GnRH; 2) estrogen acts at the pituitary to block its response to GnRH for 6-12 h and enhances the accumulation of releasable LH; and 3) magnitude of the LH surge is dependent on the amount of GnRH stimulation.}, number={3}, journal={BIOLOGY OF REPRODUCTION}, author={BRITT, JH and ESBENSHADE, KL and ZIECIK, AJ}, year={1991}, month={Sep}, pages={478–485} }
 @article{britt_day_webel_brauer_1989, title={Induction of fertile estrus in prepuberal gilts by treatment with a combination of pregnant mare's serum gonadotropin and human chorionic gonadotropin}, volume={67}, DOI={10.2527/jas1989.6751148x}, abstractNote={Ten trials involving 678 presumed prepuberal gilts (5.5 to 7.5 mo old) were conducted in North Carolina, Illinois and Missouri to evaluate the reproductive performance of gilts given a combination of 400 IU of pregnant mare's serum gonadotropin and 200 IU of human chorionic gonadotropin (P. G. 600). Gilts that were presumed to be prepuberal received P. G. 600 or no treatment (control) on the day of movement from finishing facilities to pens for breeding. Detection of estrus, with the aid of mature boars, was conducted daily for 28 d; gilts in estrus were mated naturally. Treatment with P. G. 600 increased the percentage in estrus within 7 (57.5 vs 40.9%) or 28 d (72.9 vs 59.5%); average interval to estrus was reduced (P less than .05) from 10.4 to 7.5 d. Farrowing rate (78.5 +/- 3.1%), number of pigs born alive (8.6 +/- .2) or dead (.26 +/- .06) and number of pigs weaned (8.0 +/- .2) were unaffected by treatment. Gilts that were heavier than the median for each farm were in heat sooner and more were detected in heat, but no other reproductive traits differed between heavy and light gilts. Overall, the results reveal that P. G. 600 was useful for induction of fertile estrus in prepuberal gilts.}, number={5}, journal={Journal of Animal Science}, author={Britt, Jack and Day, B. N. and Webel, S. K. and Brauer, M. A.}, year={1989}, pages={1148} }
 @article{britt_scott_armstrong_whitacre_1986, title={DETERMINANTS OF ESTROUS BEHAVIOR IN LACTATING HOLSTEIN COWS}, volume={69}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(86)80653-1}, abstractNote={The objective was to determine factors that affect the expression of estrus. Thirteen lactating Holstein cows were ovariectomized about 4 to 6 wk postpartum and then challenged repeatedly with progesterone and estradiol benzoate to induce estrus six times during the postpartum period. Each challenge included 5 d when the cow was primed with progesterone through insertion of a progesterone-impregnated, foam rubber pessary. Estradiol benzoate (1 mg) was injected intramuscularly 36 h after removal of the pessary. Groups of two to three cows each began the experiment at 3-mo intervals to avoid confounding treated simultaneously. Observations for estrous behavior were at 8-h intervals following each challenge. A minimum of three sexually active cows were always observed together to avoid differences in estrous behavior caused by having too few sexually active animals in the group. Observations for estrous behavior were at 8-h intervals following each challenge. During each observation, cows were observed for 30 min on dirt and for 30 min on concrete. Standing behavior was not influenced by postpartum interval, season of year, or milk yield. Mounting behavior increased from the first to the sixth postpartum challenge, but it was not affected by season of year or milk yield. Duration of estrus, mounting activity, and standing activity were greater on dirt than on concrete. These results indicate that the surface on which cows were observed had a profound effect on sexual behavior; however, postpartum interval, season of year, and milk yield were of minor importance.}, number={8}, journal={JOURNAL OF DAIRY SCIENCE}, author={BRITT, JH and SCOTT, RG and ARMSTRONG, JD and WHITACRE, MD}, year={1986}, month={Aug}, pages={2195–2202} }
 @article{britt_1985, title={ENHANCED REPRODUCTION AND ITS ECONOMIC-IMPLICATIONS}, volume={68}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(85)80997-8}, abstractNote={Reproductive performance affects profit of dairy herds because it directly affects milk produced per cow per day, number of replacements produced, and rates of voluntary and involuntary culling. High producing cows will reproduce at a satisfactory rate if they are managed properly. There appears to be direct relationship between herd management and reproductive performance. Thus, reproductive performance and profit respond positively to improvements of rates of detection of estrus, improvements of rates of conception, and improvements of management of the periparturient cow. Pharmacological procedures are now available for controlling time of estrus and insemination in groups of cattle. It is feasible to limit the breeding period in a herd to 1 wk of each 3-wk interval. Primary benefits of controlled breeding are convenience and efficient use of labor for detection of estrus and insemination. Biotechnical procedures such as embryo transfer and insertion of specific genes may enhance rates of genetic improvement for important economic traits.}, number={6}, journal={JOURNAL OF DAIRY SCIENCE}, author={BRITT, JH}, year={1985}, pages={1585–1592} }
 @article{britt_szarek_levis_1983, title={Characterization of summer infertility of sows in large confinement units}, volume={20}, DOI={10.1016/0093-691X(83)90032-8}, abstractNote={Data were from 3119 farrowings in three large swine confinement units in eastern North Carolina. Litters were weaned during April through October. Interval to first estrus after weaning was greater during June through September than during other months. The two-way interactions among farm unit, parity and month weaned all affected weaning-to-estrus interval. Conception rate at first estrus was lower for primiparous than for multiparous sows and declined from April through July. Conception rate at first estrus was affected by farm by parity interaction. Weaning-to-conception interval was longer for primiparous than multiparous sows and was longer during June through October. Weaning-to-conception interval was affected by interactions of unit with parity and unit with month weaned. Total pigs farrowed at the subsequent farrowing was affected by unit, parity, length of the previous lactation and the unit × parity interaction. Overall, reproductive performance varied among farm units, was lower in primiparous than in multiparous sows and was reduced during June through October.}, number={1}, journal={Theriogenology}, author={Britt, Jack and Szarek, V. E. and Levis, D. G.}, year={1983}, pages={133} }
 @article{britt_levis_1982, title={EFFECT OF ALTERING SUCKLING INTERVALS OF EARLY-WEANED PIGS ON REBREEDING PERFORMANCE OF SOWS}, volume={18}, ISSN={["0093-691X"]}, DOI={10.1016/0093-691X(82)90104-2}, abstractNote={Sows on two commerical farms were assigned to have their pigs weaned after a 3-week lactation (control, n=160) or after a 3-week lactation that included a 48-hr period of interrupted nursing before weaning (altered-suckling, n=122). Sows in the altered-suckling groups were paired, and each member of a pair was separated from both litters during the alternate 12-hr periods. Thus during the final 48 hr before weaning, each sow in the altered-suckling group had two 12-hr periods when no litters were present and two 12-hr periods when two litters were present. On farm 1, interval from weaning to estrus was 12.8 ± 0.8 days for control sows compared to 8.4 ± 1.0 days for sows in the altered-suckling group (P<.01). On farm 2, interval from weaning to estrus did not differ between sows in the control group and those in the altered-suckling group (6.2 vs 6.1 days, P>.05). Thus altered-suckling was effective in reducing the interval from weaning to estrus only when the normal rebreeding interval was prolonged (farm 1). Conception rates at first breeding and subsequent litter sizes did not differ between treatments. Altered-suckling may improve reproductive performance of sows in situations where prolonged postweaning anestrus is a problem.}, number={2}, journal={THERIOGENOLOGY}, author={BRITT, JH and LEVIS, DG}, year={1982}, pages={201–207} }
 @article{britt_1979, title={New concepts in managing dairy cattle reproduction}, ISBN={0470266724}, journal={Animal reproduction : invited papers}, publisher={John Wiley and Sons}, author={Britt, J. H.}, year={1979}, pages={63} }