The overall objective of my research is to improve the understanding of the endocrine mechanisms regulating growth and reproduction in domestic animals. By measuring hormonal differences between livestock that grow at different rates and those that reproduce successfully and those that did not we may be able to select animals that will provide superior performance or use pharmacological methods to improve livestock performance.
Reproduction in Heat Stressed Dairy Cows: Reproductive performance drastically declines in lactating dairy cows during the warm months of the year. A number of factors such as hormone concentrations, follicular growth patterns and uterine environment have been found to differ between heat stressed and non-heat stressed cows. Modifying the housing to improve cooling only partially alleviates the problem. Wee have shown that administration of hormones such as gonadotropin releasing hormone (GnRH) or human chorionic gonadotropin (hCG) increased pregnancy rates in heat stressed cows. Currently we are investigating the use of follicle stimulating hormone (FSH) to try and improve follicular growth in heat stressed cows. We have also looked at differences in concentrations of hormones and metabolites between heat stressed and non-heat stressed cows.
In addition to these studies we have conducted estrous synchronization research in both beef and dairy cows. These applied studies have primarily focused on timed artificial insemination with heifers and comparison of different types of progesterone drugs and delivery systems. Wee found that melengestrol acetate (MGA) an orally active form of progesterone was just as effective as the CIDRÔ (an intravaginal progesterone releasing device) in synchronizing postpartum beef cows.
Beef Cattle Efficiency: As part of a team of researchers including nutritionists and geneticists I am investigating physiological and behavioral differences between cattle that differ in their efficiency of growth. Some animals gain more weight than predicted based on the amount of feed they consume and others gain less. The first type is more desirable for producers. Using bulls we have found that more efficient cattle are calmer, eat more rapidly and are leaner than less efficient cattle. Currently we are measuring concentrations of hormones known to regulate metabolism and growth. In the next few years we will continue these studies and extend them to heifers and cows to determine if the same genetic lines are more efficient in both sexes.
Hormone Concentrations in Animal Waste: All animals excrete hormones in their waste and these can be measured in urine, feces and saliva. In large farms where there are thousands of animals the waste could contain levels of hormones that can affect aquatic wildlife. We are currently developing methods for measuring hormone concentrations in swine manure and in fields which have been fertilized with swine manure and water runoff from those fields.
We are collaborating with a researcher interested in the effects of housing type and diet on stress in zoo animals, especially primates. Concentrations of the hormone cortisol are often used as an indicator of stress but blood samples cannot be taken from these animals without stressing them. We have developed assays for cortisol and some of its metabolites in saliva, urine and feces, which can be collected without stress to the animal. This research may lead to improvements in housing for these species.
Pinto, C.R.F., D.M. Kozink, M.D. Whitacre, C.S. Whisnant. Utilization of a semi-quantitative ELISA progesterone kit in broodmare management. Anim Repro Sci 94:204-206, 2006.
Barker, C. K. Echeverria, M. Davis, C.S. Whisnant, C.R.F. Pinto. Effects of different doses of PGF2 alpha on luteal function and the subsequent estrous cycle. Anim Repro Sci 94:207-209, 2006.
Stalhut, H.S., C.S. Whisnant, K.E. Lloyd, E.J. Baird, L.R. Legleiter, S.L. Hansen, J.W. Spears. Efect of chromium supplementation and copper status on glucose and lipid metabolism in Angus and Simmental beef cows. Anim Feed Sci Technol 128:253-265, 2006.
Stalhut, H.S., C.S. Whisnant, J.W. Spears. Efect of chromium supplementation and copper status on reproduction in beef cows. Anim Feed Sci Technol 128:266-273, 2006.
Oliver, W.T., K.J. Touchette, J.A. Coalson, C.S. Whisnant, J.A. Brown, S.A. Mathews Oliver, J. Odle, and R.J. Harrell. Pigs weaned from the sow at 10 d of age respond to dietary energy source of manufactured liquid diets and exogenous porcine somatotropin (pST). J Anim Sci 83:1002-1009.
Walker, S., O.W. Robison, C.S. Whisnant, J.P. Cassady. Effect of divergent selection for testosterone production on testicular morphology and daily sperm production in boars. J. Anim Sci 82:2259-2263, 2004.
Willard, S., S. Gandy, S. Bowers, K. Graves, A. Elias, C.S. Whisnant. The effects of GnRH administration on serum concentrations of progesterone and pregnancy rates in dairy cows exposed to mild summer heat stress. Theriogenology 59:1799-1810, 2003.
Whisnant, C.S., R.J. Harrell. Effect of short-term feed restriction and refeeding on serum concentrations of leptin, luteinizing hormone and insulin in ovariectomized gilts. Dom. Anim. Endocrinol. 22:73-80, 2002.
Lloyd, K.E., C.S. Whisnant, G.W. Huntington, J.W. Spears. Effect of long-chain fatty acids on growth, reproductive performance and metabolite concentrations in pubertal beef heifers and postpartum cows. Prof. Anim. Scientist 18:66-73, 2002.
Whisnant, C.S., P. Burns. Evaluation of steroid microspheres for control of estrus in cows and induction of puberty in heifers. Theriogenology 58:1229-1235, 2002.
Whisnant, C.S., L.A. Pagels, M.G. Daves. Effectiveness of a commercial early conception factor test for use in pregnancy detection in cattle. Professional Animal Scientist, 17:51-54, 2001.
Reed, B.K., C.S. Whisnant. Effects of monensin and forage:concentrate ratio on feed intake, endocrine and ovarian function in beef heifers. Animal Reprod. Sci. 67:171-180, 2001.
Melton, C. M., G. M. Zaunbrecher, G. Yoshizaki, R. Patino, C. S. Whisnant, A. Rendon, V. H. Lee. Expression of connexin-43 mRNA and protein in developing follicles of prepubertal porcine ovaries. Comp. Biochem. Physiol. 130:43-55, 2001.
Haden, N.P., J.R. Hickox, C.S. Whisnant, D.M. Hardy. Systematic characterization of sperm-specific membrane proteins in swine. Biol. Reprod. 63:1839-1847, 2000.
Whisnant, C.S., S.P. Washburn, P.W. Farin. Current concepts in synchronization of estrus and ovulation in dairy cows. Proc. Am. Soc. Anim. Sci. 1999. Available at http://www.asas.org/JAS/symposia/proceedings/0032.pdf
Geiger, T.L., M.Z. Khan, C.S. Whisnant, S.D. Prien, S. A. Khan. Regulation of DNA synthesis in Leydig cells obtained from neonatal pig testes. Dom. Anim. Endocrinol 17: 65-75. 1999.
Whisnant, C.S., R.S. Kline, J.C. Branum, G.M. Zaunbrecher, M.Z. Khan, S.P. Jackson. Hormonal profiles of callipyge and normal sheep. J. Anim. Sci. 76:1443-1447. 1998.
Whisnant, C.S., A.M. Benoit, R.A. Dailey. Concentrations of tissue-type plasminogen activator and relaxin in normal and induced-cystic follicles in gilts. Dom. Anim. Endocrinol.15:169-176. 1998.
Johnson, N.N., H.A. Brady, C.S. Whisnant, P.A. LaCasha. Effects of oral altrenogest on sexual and aggressive behaviors and seminal parameters in young stallions. J. Equine Vet. Sci. 18:249-253. 1998.
Hicks, T.A., J.J. McGlone, C.S. Whisnant, H.G. Kattesh, and R.L. Norman. Behavioral, endocrine, immune and performance measures for pigs exposed to acute stress. J. Anim. Sci. 76:474-483. 1998.
Branum, J.C., R.S Kline, and C.S Whisnant. The effects of neurotransmitter antagonists and glucose on LH secretions in growth-restricted wethers. Anim. Reprod. Sci. 45:263-272. 1997.
Salak-Johnson, J.L., J.J. McGlone, C.S. Whisnant, R.L. Norman, and R.R. Kraeling. Intracerebro-ventricular porcine corticotrophin releasing hormone and cortisol effects on pig immune measures and behavior. Physiol. Behav. 61:15-24. 1997.