51AV

Reproductive Physiology and Endocrinology Laboratory

Research

Poultry is a common domestic species that plays an important role in agriculture by generating over 35 billion dollars per year. However, rapid growth rate in broilers is known to be associated with pulmonary hypertension syndrome (ascites). Ascites causes substantial economic losses due to mortality and condemnation in poultry. The long-term goal in our research program is to develop and implement effective interventions that will improve the health of poultry, especially those that are susceptible to ascites. Our central hypothesis is that ghrelin is a key hormone involved in feed intake, energy homeostasis, spatial short-term memory and cardiovascular function in birds. Using complementary experimental strategies that have been validated in our laboratory, we aim to up- and down-regulate the activity of ghrelin in broiler chickens and turkeys to evaluate the effect of this gut-brain hormone in animal health.

People

Graduate Students

All graduate students (MS and PhD) pursuing the Animal Health curriculum (Food and Animal Science) actively participate in research associated with poultry species.

Undergraduate Students:

Undergraduate students undergoing the Animal Bio-Health Sciences program that are interested in research, have the opportunity to work in our lab. Students are exposed to various hands-on research techniques in the Poultry Building or at the Reproductive Physiology and Endocrinology Laboratory.

Publications

Peer-reviewed publications and books.

1. Vizcarra, F. R., M. Verghese, and J. A. Vizcarra. 2018. Effect of short- and long-term feed restriction on ghrelin concentrations in turkeys. Poultry Science 97(6) 2183–2188.
2. Lents, CA., Looper, ML., Ojeda, AJ., Vizcarra, JA, and Wettemann, RP. 2015. Removal of ruminal contents followed by restricted feeding does not affect the frequency of luteinizing hormone pulses in steers. The Professional Animal Scientist 31:349-353.
3. Kirby, J. and Vizcarra, J. 2015. Regulation of FSH secretion in broiler breeders. Rev. Bras. Reprod. Anim. 39(1) 91:96.
4. Mutai, E., Sunkara, R., Vizcarra, J., Walker, L. and Verghese, M. 2015. Antioxidant, Enzyme Inhibitory and Anti-Obesity Potential of Sorrel Calyx Extracts in 3T3-L1 Adipocytes. Food and Nutrition Sciences, 6, 452-465. doi: 10.4236/fns.2015.65047.
5. Vizcarra, J., Alan, R., and Kirby, J. 2015. Chapter 29 - Reproduction in Male Birds. In C. G. Scanes (Ed.), Sturkie's Avian Physiology (Sixth Edition) (pp. 667-693). San Diego: Academic Press.
6. Vizcarra, J.A. 2013. Gonadotropins. Editor. ISBN: 978-953-51-1006-4, InTech, DOI: 10.5772/47863.
7. Vizcarra, J.A. 2013. Contribution of Chicken GnRH-II and Lamprey GnRH-III on Gonadotropin Secretion, Gonadotropin, Dr. Jorge Vizcarra (Ed.), ISBN: 978-953-51-1006-4, InTech, DOI: 10.5772/47863.
8. Vizcarra, J., H. Wright, and A. Vizcarra. 2012. The effect of passive immunization against ghrelin on feed and water intake in turkeys. Poult. Sci. 91 (9) 2305-2309.
9. Vizcarra, J.A. 2012. Differential feed intake in mammalian and avian species: Immunization against ghrelin. Archivos Latinoamericanos de Producción Animal 20(3-4):113-117.
10. Vizcarra, J.A., R.P. Wettemann, and S.L. Karges. 2012. Immunization of beef heifers against gonadotropin-releasing hormone prevents luteal activity and pregnancy: Effect of conjugation to different proteins and effectiveness of adjuvants. J Anim Sci. 90(5):1479-88.
11. Barretero-Hernandez, R., M. Galyean, and J. Vizcarra. 2010. The Effect of Feed Restriction on Plasma Ghrelin, Growth Hormone, Insulin, and Glucose Tolerance in Pigs. The Professional Animal Scientist. 26(1):26–34.
12. Vizcarra, J.A., J. Kirby, and D. Kreider. 2010. Testis Development and Gonadotropin Secretion in Broiler Breeder Males. Poult. Sci. 89:328-334.
13. Barretero-Hernandez, R., J.A. Vizcarra, A. Bowen, and M. Galyean. 2010. Lamprey GnRH-III releases luteinizing hormone but not follicle stimulating hormone in pigs. Reprod. Domest. Anim. 45(6):983-987.
14. Arelovich, H., C. Abney, J. Vizcarra, and M. Galyean. 2008. Effects of Dietary Neutral Detergent Fiber on Intakes of Dry Matter and Net Energy by Dairy and Beef Cattle: Analysis of Published Data. The Professional Animal Scientist 24:375-383.
15. Vizcarra, J.A., J.D. Kirby, S.K. Kim, and M.L. Galyean. 2007. Active immunization against ghrelin decreases weight gain and alters plasma concentrations of growth hormone in growing pigs. Domest. Anim. Endocrinol. 33(2): 176-189.
16. Bowen, A., S. Khan, L. Berghman J.D. Kirby, R.P. Wettemann, and J.A. Vizcarra. 2006. Immunization of pigs against chicken GnRH-II and lamprey GnRH-III: Effects on gonadotropin secretion and testicular function. J. Anim. Sci. 84(11):2990-9.
17. Vizcarra, J.A., and J.J. Ford. 2006. Validation of the sperm mobility assay in boars and stallions. Theriogenology. 66(206): 1091-1097.
18. McDonald, C.A., A.C. Millena, S. Reddy, S. Finlay, J.A. Vizcarra, S.A. Khan, and J.S. Davis. 2006. FSH-Induced Aromatase in Immature Rat Sertoli Cells Requires an Active Phosphatidylinositol 3-kinase Pathway and is Inhibited via the Mitogen-activated Protein Kinase Signaling Pathway. Mol. Endocrinol. 20(3):608-618.
19. Kirby, J.D., J.A. Vizcarra, L.R. Berghmann, J.A. Proudman, J. Yang and C.G. Scanes. 2005. Regulation of FSH secretion: GnRH independent? In: Functional Avian Endocrinology. A Dawson & P J Sharp (Eds). Narosa Publishing House, New Delhi, India. p. 83-96 (ISBN: 81-7319-568-4).
20. Cornett, L.E., J.D. Kirby, J.A. Vizcarra, J.C. Ellison, J. Thrash, P.R. Mayeux, M.D. Crew, S.M. Jones, N. Ali, and D.A. Baeyens. 2005. Molecular cloning and functional characterization of a vasotocin receptor subtype expressed in the pituitary gland of the domestic chicken (Gallus domesticus): avian homolog of the mammalian V1b-vasopressin receptor. GenBank Accession Number NM_001031498.
21. Vizcarra, J.A., D.L. Kreider, and J.D. Kirby. 2004. Episodic gonadotropin secretion in the mature fowl: serial blood sampling from unrestrained male broiler breeders (Gallus domesticus). Biol. Reprod. 70(6):1798-805.
22. Cornett, L.E., J.D. Kirby, J.A. Vizcarra, J.C. Ellison, J. Thrash, P.R. Mayeux, M.D. Crew, S.M. Jones, N. Ali, and D.A. Baeyens. 2003. Molecular cloning and functional characterization of a vasotocin receptor subtype expressed in the pituitary gland of the domestic chicken (Gallus domesticus): avian homolog of the mammalian V1b-vasopressin receptor. Regul. Pept. 110:231-9.
23. Looper, M.L., J.A. Vizcarra, R.P. Wettemann, J.R. Malayer, T.D. Braden, R.D. Geisert, and G.L. Morgan. 2003. Influence of estradiol, progesterone, and nutrition on concentrations of gonadotropin and GnRH receptors, and gene expression of GnRH receptors and gonadotropin subunits in pituitaries of beef cows. J. Anim. Sci. 81:269-278.
24. Prado, T.M., R.P. Wettemann, L.J. Spicer, J.A. Vizcarra, and G.L. Morgan. 2002. Influence of exogenous gonadotropin-releasing hormone on ovarian function in beef cows after short- and long-term nutritionally induced anovulation. J. Anim. Sci. 80:3268-76.
25. Lents, C.A., R.P. Wettemann, M.J. Paape, J.A. Vizcarra, M.L. Looper, D.S. Buchanan, and K.S. Lusby. 2002. Efficacy of intramuscular treatment of beef cows with oxytetracycline to reduce mastitis and to increase calf growth. J. Anim. Sci. 80:1405-1412.
26. Bacon, W.L., J.A. Vizcarra, J.L. Morgan, J. Yang, K. Liu, D.W. Long, and J.D. Kirby. 2002. Changes in Plasma Concentrations of Luteinizing Hormone, Progesterone, and Estradiol-17β in Peripubertal Turkey Hens Under Constant Lighting or 14L:10D Photoperiods. Biol. Reprod. 67: 591-598.
27. Yang, J., J. Vizcarra, R. Okimoto, and J. Kirby. 2002. Gallus gallus follicle-stimulating hormone beta gene, exons 1, 2 and 3 and complete cds. The chicken follicle-stimulating hormone beta subunit gene. GenBank Accession Number AF467082
28. Ali, N., L.E. Cornett, J.A. Vizcarra, J.D. Kirby, and D.A. Baeyens. 2001. Molecular cloning and pharmacological characterization of a vasotocin receptor subtype that is expressed in the pituitary gland of the domestic chicken. GenBank Accession Number AY008272.
29. Bossis, I., R.P. Wettemann, S.D. Welty, J.A. Vizcarra, and L.J. Spicer. 2000. Nutritionally induced anovulation in beef heifers: ovarian and endocrine function during realimentation and resumption of ovulation. Biol. Reprod. 62(5): 1436-1444.
30. Arelovich, H., F.N. Owens, G.W. Horn, and J.A. Vizcarra. 2000. Effects of supplemental zinc and manganese on ruminal fermentation, diet intake and digestibility in cattle fed prairie hay and urea. J. Anim. Sci. 78:2972-2979.
31. Looper, M.L., J.A. Vizcarra, and R.P. Wettemann. 2000. Estrus and Luteal Activity of Postpartum Beef Cows after Treatment with Gonadotropin-Releasing Hormone and Prostaglandin F_2a. The Professional Animal Scientist 16(4): 207-212.
32. Vizcarra, J.A., R.P. Wettemann, and G.L. Morgan. 1999. Influence of dose, frequency and duration of infused gonadotropin releasing hormone on secretion of luteinizing hormone and follicle-stimulating hormone in nutritionally anestrous beef cows. Domest. Anim. Endocrinol. 16(3): 171-181.
33. Bossis, I., R.P. Wettemann, S.D. Welty, J.A. Vizcarra, L.J. Spicer, and M.G. Diskin. 1999. Nutritionally induced anovulation in beef heifers: ovarian and endocrine function preceding cessation of ovulation. J. Anim. Sci. 77:1536-1546.
34. Hamilton, T.D., J.A. Vizcarra, R.P. Wettemann, B.E. Keefer, and L.J. Spicer. 1999. Ovarian function in nutritionally induced anoestrous cows: effect of exogenous gonadotropin-releasing hormone in vivo and effect of insulin and insulin-like growth factor I in vitro. J. Reprod. Fertil. 117:179-187.
35. Vizcarra, J.A., R.P. Wettemann, J.C. Spitzer, and D.G. Morrison. 1998. Body condition at parturition and postpartum weight gain influence luteal activity, glucose, insulin and NEFA concentrations in primiparus beef cows. J. Anim. Sci. 76:927-936.
36. Vizcarra, J.A. 1998. International markets hold potential for U.S. meats. In: Special Report. Feedstuffs 70(3): 1-47.
37. Vizcarra, J.A., R.P. Wettemann, T. Braden, A.M. Turzillo, and T. Nett. 1997. Effect of gonadotropin-releasing hormone (GnRH) pulse frequency on serum and pituitary concentrations of luteinizing hormone and follicle-stimulating hormone, GnRH receptors, and messenger ribonucleic acid for gonadotropin subunits in cows. Endocrinology 138:594-601.
38. Vizcarra, J.A., and R.P. Wettemann. 1996. Reproducibility, repeatability and degree of expertise required to asses body condition score in beef cattle. The Professional Animal Scientist 12:28-31.
39. Vizcarra, J.A., R.P. Wettemann, and D.K. Bishop. 1995. Relationship between puberty in heifers and the cessation of luteal activity after nutritional restriction. Animal Science 61:507.
40. Cavestany, D., J. Vizcarra, W. Cardozo, F. Perdigón, R. Tagle, S. Quma, and S. Lanzzeri. 1990. Studies on post-partum reproductive performance of Hereford beef cows in Uruguay with the aid of progesterone assay. In: Livestock reproduction in Latin America. p. 257-267 (ISBN: 92-0-111290-4).
41. Vizcarra, J.A., J.M. Mieres, and D.Vaz Martins. 1986. The effect of different growth parameters and some characteristics of the carcass, on the composition, dressing percentage and weight of valuable retail cuts of Hereford steers (II). (Efecto de distintos parámetros de crecimiento y caracteríticas de la res en la composición, rendimiento y peso de cortes valiosos del cuarto trasero de novillos Hereford II). Investigaciones Agronómicas 7: 37-44.
42. Vizcarra, J.A., W. Ibañez, and R. Orcasberro. 1986. Repeatability and reproducibility of two systems to evaluate body condition in Hereford beef cows. (Repetiblidad y reproductibilidad de dos escalas para estimar la condición corporal de vacas Hereford). Investigaciones Agronómicas. 7:45-47.
43. Vizcarra, J.A., J.M. Mieres, and D. Vaz Martins. 1985. The effect of different growth parameters and some characteristics of the carcass, on the composition, dressing percentage and weight of valuable retail cuts of Hereford steers (I). (Efecto de distintos parámetros de crecimiento y caracteríticas de la res en la composición, rendimiento y peso de cortes valiosos del cuarto trasero de novillos Hereford I). Investigaciones Agronómicas 6:60-67.

Abstracts for professional societies, proceedings, trade journals and popular press

1. Ceron-Romero, N, N. Taofeek, A. Thomas, H. Chance, E. Vroonland, M. Verghese, and J. Vizcarra. 2019. The Effect of ghrelin antagonist (D-Lys3) GHRP-6 on feed intake in broiler chickens (Gallus gallus domesticus). STEM Day 2019. 51AV A&M University. Abstract #18.
2. Ceron-Romero, N, N. Taofeek, A. Thomas, J. Johnson, R. Winter, M. Verghese, and J. Vizcarra. 2019. The Effect of Feed Restriction and Mild Hypothermia on Concentrations of Ghrelin, Corticosterone and Pulmonary Arterial Pressure in Broiler Chickens (Gallus gallus domesticus). Association of Research Directors. Jacksonville, FL. (Abs p ).
3. Taofeek, N., F. Vizcarra, M. Verghese, and J.A. Vizcarra. 2018. The effect of Feed Restriction on ghrelin, glucose and Insulin concentrations in male broiler chickens. STEM Day 2018. 51AV A&M University. Abstract #17.
4. Taofeek, N., F. Vizcarra, M. Verghese, and J.A. Vizcarra. 2018. The effect of Feed Restriction on ghrelin concentrations in male broiler chickens. International Poultry Scientific Forum. Atlanta, Georgia. (M3 p 1).
5. Vizcarra, F.R., H. Wright, R. Long, M. Verghese, and J.A. Vizcarra. 2017. The Effect of Short- and Long-Term Feed Restriction on Ghrelin Concentrations in Turkeys. Association of Research Directors. Atlanta, Georgia. (Abs 421 p 193).
6. Long, R., Campos, A., Vizcarra, F., Gibson, M., Verghese, M., and Vizcarra, J. 2015. The Effect of Long-Term Feed Restriction on Ghrelin Concentrations in Turkeys. STEM Day 2015. 51AV A&M University. Abstract #41.
7. Vizcarra, F., Wright, H., Long, R. and Vizcarra, J. 2014. Preprandial Concentrations of Ghrelin in Turkeys. STEM Day 2014. 51AV A&M University. Abstract #45. First Place in Abstract Competition.
8. Wright, H, K. Portis, J. Sharpe, F. Archer, and J. Vizcarra. 2013. Animal Welfare: A Perspective among Faculty Members. STEM Day 2013. 51AV A&M University. Abstract #25.
9. Vizcarra, J.A. 2012. The effect of body condition on reproductive traits in beef cattle. XX International congress on agricultural technology transfer. Asuncion, Paraguay. pp 13-21.
10. Coriasso, C., I. Davis, C. Turner, N. Armstrong, K. Bellignheri, F. Archer, and J. Vizcarra (advisor). 2012. Attitudes Toward Agricultural Animal Welfare at AAMU: A capstone project. STEM Day 2012. 51AV A&M University. Abstract #74.
11. Peterson, M., J. Matthews, J. Khatiwada, J. Vizcarra, A. Gueye, and G. Abdelrahim (advisor). 2012. Effect of dietary supplementation of ferrous sulfate on performance and carcass characteristics of meat sheep. STEM Day 2012. 51AV A&M University. Abstract #79.
12. Wright, H., and Vizcarra, J.A. 2012. The orexigenic and behavioral effects of passive immunization against ghrelin in turkeys. CALNS Research presentation day. Presentation #3.
13. Vizcarra, J. 2011. Vaccination against Ghrelin: differential feed intake in mammalian and avian species. Proceedings XXII ALPA meeting 19:5.
14. Bush, A., R. Kantety, J. Vizcarra, G. Abdelrahim, and K. Konan (advisor). 2011. cDNA construction, cloning and sequencing of full length cDNA from tuber crop yam (Dioscorea sp.). STEM Day 2011. 51AV A&M University. Abstract #45. Award: 1^st place Graduate competition.
15. Matthews, J., J. Khatiwada, J. Vizcarra, and G. Abdelrahim (advisor). 2011. Feeding value of peanut skins for meat sheep. STEM Day 2011. 51AV A&M University. Abstract #56.
16. Peterson, M., J. Khatiwada, J. Vizcarra, and G. Abdelrahim (advisor). 2011. Carcass characteristics of wether lambs fed increasing levels of distillers dried grains with soluble. STEM Day 2011. 51AV A&M University. Abstract #57.
17. Vizcarra, A., H. Wright, L. Shackelford, G. Abdelrahim, and J. Vizcarra (advisor). 2011. The effect of passive immunization against ghrelin on feed intake in turkeys. STEM Day 2011. 51AV A&M University. Abstract #58.
18. Wright, H., A. Vizcarra, L, Shackelford, G. Abdelrahim, and J. Vizcarra (advisor). 2011. The effect of anti-ghrelin antibodies on turkey behavior. STEM Day 2011. 51AV A&M University. Abstract #59.
19. Vizcarra, A., H. Wright, L. Shackelford, G. Abdelrahim, D. Washington, and J.A. Vizcarra. 2011. Orexigenic Effects of Anti-Ghrelin Antibodies in Broad-Breasted White Turkeys. Association of Research Directors. Atlanta, Georgia. (Abs P-SP-U-30 p 173).
20. Wright, H., A. Vizcarra, L. Shackelford, G. Abdelrahim, and J. Vizcarra. 2011. The Effect of Passive Immunization Against Ghrelin on Animal Behavior. Association of Research Directors. Atlanta, Georgia. (Abs P-SP-U-34 p 174).
21. Matthews, J., G. Abdelrahim, J. Khatiwada, and J. Vizcarra. 2011. Impact of feeding peanut skins on carcass characteristics of meat sheep. Association of Research Directors. Atlanta, Georgia. (Abs P-SP-U-22 p 170).
22. Peterson, M., G. Abdelrahim, J. Khatiwada, and J. Vizcarra. 2011. Carcass characteristics of wether lambs fed increasing levels of distillers dried grains. Association of Research Directors. Atlanta, Georgia. (Abs P-SP-U-24 p 171).
23. Abdelrahim, G., J. Khatiwada, D. Rankins, N. Gurung., and J. Vizcarra. 2010. Carcass characteristics of sheep fed peanut skins. J. Anim. Sci. (Abs 95).
24. Vizcarra, J.A., R. Barretero-Hernandez, A. Bowen, and B. Tilley. 2009. Lamprey GnRH-III selectively releases luteinizing hormone but not follicle stimulating hormone in pigs. 15^th Biennial Research Symposium. Association of Research Directors. Atlanta, Georgia. (Abs P-159).
25. Vizcarra, J., R. Barretero, A. Bowen, and B. Tilley. 2008. The effect of peripheral administration of lamprey GnRH-III on gonadotropin secretion by pigs. 6^th International congress on Farm Animal Endocrinology. Roanoke, Virginia. (Abs 38).
26. Vizcarra, J.A. 2008. La condición corporal en rodeos de cría: del campo al laboratorio. Congreso Argentino de Producción Animal. (Key note speaker).
27. Vizcarra, J.A. 2005. Ghrelin: an endocrine signal linking nutrition and reproduction. Reproduction in Domestic Animals 40(4): 393 (Abs P214).
28. Bowen, A., S. Khan, L. Berghman, J.D. Kirby, and J.A. Vizcarra. 2005. Immunization of pigs against chicken (c)GnRH-II and lamprey (l)GnRH-III: Effects on gonadotropin secretion and testicular function. J. Anim. Sci. (Abs 414).
29. Dehn, C., S. Finlay, and J.A. Vizcarra. 2003. Assessment of Boar Sperm Mobility Based on Accudenz Penetration. Biol. Reprod. 68(supplement 1) (Abs 408).
30. Finlay, S.B., C.A. McDonald, S.C. Reddy, J.A. Vizcarra, J.C. Davis, and S.A. Khan. 2003. Amplification of IGF-1 induced PKB/AKT phosphorylation by FSH in porcine Sertoli Cells. Biol. Reprod. 68(supplement 1) (Abs 422).
31. Vizcarra, J.A., S. Khan, L. Berghman, J. Kirby, C. Dehn, and S. Finlay. 2003. Neuroendocrine contribution of lamprey GnRH-III in the control of testicular function in pigs. IX World Conference On Animal Production (p 37).
32. Kuenzel, W.J., J.A. Vizcarra, J.D. Kirby, and S.A. Copeland. 2001. Sulfamethazine augments the photostimulatory effects of long days on gonadal development in male chicks. Soc. Neuroscience (Abs 630.20).
33. Vizcarra, J.A., M.L. Rhoads, C.C. Hsu, J. Washington, J.L. Morgan, J. Yang, H. Tang, K. Shaffer, and J.D. Kirby JD. 2001. Immunization of Male Broiler Breeders Against Mammalian Gonadotropin Releasing Hormone. Poult. Sci. (Suppl 1): (Abs 1939).
34. Shaffer, K., J.A. Vizcarra, C.C. Hsu, J.Y. Yang, M.L. Rhoads, L.E. Cornett, D. Baeyens, N. Ali, and J.D. Kirby. 2001. Vasocotin Receptor mRNA Expression in the Brain and Pituitary of Broiler Breeder Hens. Poult. Sci. (Suppl 1): (Abs 1944).
35. Vizcarra, J.A., and R.P. Wettemann. 2001. Effects of exogenous GnRH infusion and steroid replacement on gonadotropins in ovariectomized nutritionally anovulatory cows. J. Anim. Sci. (Abs 1917).
36. Vizcarra, J,A., M.L. Rhoads, and J.D. Kirby. 2000. Regulation of testis development and fertility in broilerized breeder males. Poult. Sci. 79 (Suppl 1): 78 (Abs 341).
37. Vizcarra, J.A., M.L. Rhoads, D.L. Kreider, and J.D. Kirby. 2000. Testis development and gonadotropin secretion in male broiler breeders. Poult. Sci. 79 (Suppl 1): 78 (Abs 342).
38. Vizcarra, J.A., M.L. Rhoads, C.C. Hsu, J. Washington, J.L. Morgan, J. Yang, H. Tang, J. Warren, and J.D. Kirby. 2000. Effect of immunization against chicken gonadotropin releasing hormone –I (cGnRH-I) and cGnRH-II on reproductive function in adult broiler breeder males. Poult. Sci. 79 (Suppl 1): 79 (Abs 343).
39. Kirby, J.D., J.A. Vizcarra, C. Joy, H. Hsu, M.L. Rhoads, J.L. Morgan, and D.L. Kreider. 2000. Broilerization suppresses the hypothalamo-hypophyseal-testicular axis in the fowl. VII International Symposium on Avian Endocrinology. Banaras Hindu University, Varanasi, U.P. India. (Abstract 12.02)
40. Kirby, J.D., C.J. Tressler, and J.A. Vizcarra. 2000. Effects of modern breeding practices on semen quality. World’s Poultry Science Association Lecture S3.2.03.
41. Vizcarra, J.A., W.L. Bacon, and J.D. Kirby. 2000. Physiological factors affecting the reproductive performance of commercial broiler breeder males. Proceedings 49^th National Poultry Breeders Roundtable, 97-113.
42. Vizcarra, J.A., J.L. Morgan, M.L. Rhoads, J. Hsu, H. Tang, C. Bright, and J.D. Kirby. 1999. Gonadotropin Secretion in the Mature Fowl: Serial Blood sampling from Unrestrained Male Broiler Breeders. Poult. Sci. 78 (Suppl 1): 34 (Abs 146).
43. Morgan, J.L., J. Yang, J.A. Vizcarra, D.W. Long, W.L. Bacon, and J.D. Kirby. 1999. Development of the circadian rhythms of body temperature and motor activity associated with the onset of laying in turkey hens. Poult. Sci. 78 (Suppl 1): 35 (Abs 149).
44. Kirby, J.D., J.A. Vizcarra, M.L. Rhoads, A. Shepard, J. Washington, and D.L. Kreider. 1999. FSH and testis function in broiler breeder males: Insight gained from broilerized breeder males. Poult. Sci. 78 (Suppl 1): 5 (Abs 20).
45. Looper, M.L., J.A. Vizcarra, R.P. Wettemann, J.R. Malayer, T.D. Braden, and R.D. Geisert. 1999. Influence of Progesterone and Estradiol on Pituitary Gland GnRH Receptors, Gonadotropins and Gene Expression for GnRH Receptor and Gonadotropin Subunits in Nutritionally Induced Anovulatory Beef Cows. J. Anim. Sci. 77 (Suppl. 1): 2 (Abs 4).
46. Bacon, W.L., W. Long, J.L. Morgan, J. Yang. J.A. Vizcarra, and J.D. Kirby. 1999. Frequency of luteinizing hormone (LH) surges at initiation of egg laying in turkeys photostimulated with either continuous (24L:0D) or 14L:10D lighting treatments. International Conference on Bird Reproduction. Session 5.
47. Lents, C.A., R.P. Wettemann, M.L. Looper, I. Bossis, L.J. Spicer, and J.A. Vizcarra. 1998. Concentrations of GH, IGF-I, Insulin, and Glucose in Postnatal Beef Calves. Okla. Agr. Exp. Sta. Res. Rep. 215-222.
48. Arelovich, H.M., F.N. Owens, G.W. Horn, and J.A. Vizcarra. 1998. Effects of high zinc levels on urea utilization by cattle fed prairie hay. J. Anim. Sci. (Suppl. 1) 76: (Abs 1410).
49. Vizcarra, J.A., A.G. Henandez, J.M. Bahr, W.J. Kuenzel, D.L. Kreider, and J.D. Kirby. 1998. Rescue of impaired spermatogenesis in adult male fowl following unrestricted prepubertal growth and subsequent growth restriction. Biol. Reprod. (Suppl. 1) 58: (Abs 105).
50. Bossis, I., R.P. Wettemann, J.A. Vizcarra, and L.J. Spicer. 1998. Nutritionally induced anovulation in beef heifers: ovarian and endocrine function during realimentation. Biol. Reprod. (Suppl. 1) 58: (Abs 206).
51. Lents, C.A., R.P. Wettemann, M.L. Looper, I. Bossis, L.J. Spicer, and J.A. Vizcarra. 1998. Concentrations of GH, IGF-I, insulin and glucose in beef calves after birth. J. Anim. Sci. (Suppl. 1) 76: (Abs 64).
52. Arelovich, H.M., F.N. Owens, G.W. Horn, and J.A. Vizcarra. 1997. Effects of zinc and manganese concentrations on in vitro urea degradation and prairie hay disappearance. J. Anim. Sci. (Suppl. 1) 75: (Abs 471).
53. Looper, L., C.A. Lents, J.A. Vizcarra, and R.P. Wettemann. 1997. Evaluation of the effects of body condition on luteal activity and estrus in postpartum beef cows. J. Anim. Sci. (Suppl. 1) 75: (Abs 347).
54. Vizcarra, J.A., R.P. Wettemann, and T.D. Braden. 1997. The effect of duration of nutritional anestrus and GnRH treatment on pituitary LH, FSH and GnRH receptrors in cows. J. Anim. Sci. (Suppl. 1) 75: (Abs 325).
55. Bossis, I., S.D. Welty, R.P. Wettemann. J.A. Vizcarra, and L.J. Spicer. 1997. Serum FSH, plasma estradiol and IGF-I before the onset of nutritionally induced anovulation in beef heifers. J. Anim. Sci. (Suppl. 1) 75: (Abs 326).
56. Lents, C.A., R.P. Wettemann, J.A. Vizcarra, M.L. Looper, and M.J. Paape. 1997. Dry cow treatment of beef cows: effects on mammary health and calf growth. J. Anim. Sci. (Suppl. 1) 75: (Abs 449).
57. Bossis, I., S.D. Welty, R.P. Wettemann, J.A. Vizcarra, and L.J. Spicer. 1997. Changes in serum LH and growth hormone concentrations before the onset of nutritionally induced anovulation in beef heifers. J. Anim. Sci. (Suppl. 1) 75: (S.S. Abs 65).
58. Looper, M.L., C.A. Lents, J.A. Vizcarra, and R.P. Wettemann. 1997. Effects of body condition on luteal activity and estrus in postpartum beef cows. Okla. Agr. Exp. Sta. Res. Rep. 159-162.
59. Lents, C.A., R.P. Wettemann, J.A. Vizcarra, M.L. Looper, and M.J. Paape. 1997. Dry cow treatment of beef cows. Okla. Agr. Exp. Sta. Res. Rep. 45-49.
60. Arelovich, H.M., F.N. Owens, G.W. Horn, and J.A. Vizcarra. 1997. Effects of supplemental zinc and manganese on in vitro urea degradation and prairie hay disappearance. Okla. Agr. Exp. Sta. Res. Rep. 103-108.
61. Prado, T.M., R.P. Wettemann, J.A. Vizcarra, L.J. Spicer, and L.G. Morgan. 1997. Influence of Exogenous Gonadotropin-Releasing hormone on Ovarian function in Short vs Long Nutritionally Induced Anovulatory Beef Cows. Theriogenology.
62. Bossis, I., S.D. Welty, R.P. Wettemann, J.A. Vizcarra, and L.J. Spicer. 1996. Ovarian function before the onset of nutritionally induced anovulation in heifers. J. Anim. Sci. (Suppl. 1) 74: (Abs 39).
63. Vizcarra, J.A., R.P. Wettemann, J.C. Spitzer, and D.G. Morrison. 1996. Body condition at parturition and postpartum weight gain influence luteal activity, glucose, insulin and NEFA concentrations in primiparus beef cows. J. Anim. Sci. (Suppl. 1) 74: (Abs 42).
64. Looper, M.L., R.P. Wettemann, and J.A. Vizcarra. 1996. Response of postpartum beef cows to treatment with GnRH and Prostaglandin F_2a. J. Anim. Sci. (Suppl. 1) 74: (Abs 43).
65. Lents, C.A., R.P. Wettemann, J.A. Vizcarra, M.I. Duenas, and M.J. Paape. 1996. Effect of administration of antibiotics to beef cows at weaning and calving on intramammary infections, milk somatic cell count, and calf growth. J. Anim. Sci. (Suppl. 1) 74: (Abs 44).
66. Bossis, I., S.D. Welty, R.P. Wettemann, J.A. Vizcarra, and L.J. Spicer. 1996. Pattern of follicular growth during nutritionally induced anestrus and resumption of cycles in beef heifers. J. Anim. Sci. (Suppl. 1) 74: (Abs 417).
67. Lents, C.A., R.P. Wettemann, J.A. Vizcarra, M.I. Duenas, and M.J. Paape. 1996. Effects of antibiotics on mammary function of beef cows with increased somatic cell counts in milk after parturition. J. Anim. Sci. (Suppl. 1) 74: (Abs 543).
68. Ojeda, A.J., R.P. Wettemann, J.A. Vizcarra, and F.W. Owens. 1996. The effect of acute nutrient deprivation on LH secretion and blood components in steer. J. Anim. Sci. (Suppl. 1) 74: (Abs 444).
69. Looper, M.L., J.A. Vizcarra, and R.P. Wettemann. 1996. Nutritional influence on LH and FSH pulse frequency and amplitude in beef cows: evaluation of different statistical methods. J. Anim. Sci. (Suppl. 1) 74: (Abs 445).
70. Vizcarra, J.A., R.P. Wettemann, T.D. Braden, A.M. Turzillo, and T.M. Nett. 1996. Effect of GnRH pulse frequency on pituitary concentrations of LH and FSH, GnRH receptors (GnRH-R), gonadotropin subunit mRNA, and GnRH-R mRNA in anestrous cows. J. Anim. Sci. (Suppl. 1) 74: (Abs 496).
71. Bossis, I., S.D. Welty, R.P. Wettemann, J.A. Vizcarra, and L.J. Spicer. 1996. Ovarian and endocrine changes before the onset of nutritionally induced anovulation in beef heifers. Okla. Agr. Exp. Sta. Res. Rep. P-951:309-315.
72. Looper, M.L., J.A. Vizcarra, and R.P. Wettemann. 1996. Response of postpartum beef cows to treatment with gonadotropin-releasing hormone and prostaglandin F_2a Okla. Agr. Exp. Sta. Res. Rep. P-951:317-319.
73. Looper, M.L., J.A. Vizcarra, and R.P. Wettemann. 1996. Influence of nutrition on luteinizing hormone and follicle stimulating hormone in beef cows. Okla. Agr. Exp. Sta. Res. Rep. P-951:291-294.
74. Lents, C.A., R.P. Wettemann, J.A. Vizcarra, and M.J. Paape. 1996. Administration of antibiotics to beef cows: effects on mastitis and calf growth. Okla. Agr. Exp. Sta. Res. Rep. P-951:81-84.
75. Lents, C.A., R.P. Wettemann, H.T. Purvis II, and J.A. Vizcarra. 1996. Influence of feed and water deprivation, calf sex, and early weaning on blood components and estradiol concentrations in beef calves. Okla. Agr. Exp. Sta. Res. Rep. P-951:285-289.
76. Vizcarra, J.A., and R.P. Wettemann. 1995. Precision of body condition scoring in beef cattle. J. Anim. Sci. (Suppl. 1) 73:29. (Abs 107).
77. Vizcarra, J.A., R.P. Wettemann, J.V. Yelich, and S.D. Welty. 1995. Effect of GnRH pulse frequency on secretion of LH and FSH and luteal activity in nutritionally anestrous cows. J. Anim. Sci. (Suppl. 1) 73:223. (Abs 454).
78. Hamilton, T.D., L.J. Spicer, R.P. Wettemann, and J.A. Vizcarra. 1995. Influence of exogenous gonadotropin-releasing hormone on ovarian function in nutritionally anestrous cows. J. Anim. Sci. (Suppl. 1) 73:234. (Abs 498).
79. Wettemann, R.P., and J.A. Vizcarra. 1995. Age and season influence the body condition of cows at the onset of nutritionally induced anoestrus. Journal of Reproduction and Fertility 15:66. (Abs 193).
80. Vizcarra, J.A., R.P. Wettemann, K.S. Lusby, G.E. Selk, and J.V. Yelich. 1995. Body condition score is a precise tool to evaluate beef cows. Okla. Agr. Exp. Sta. Res. Rep. P-943:201-205.
81. Wettemann, R.P., J.A. Vizcarra, T. Anderson, S. Brown, C. Burtrum, J. Hallock, E. Nesamvuni, T. Prado, and M. Sumter. 1995. Influence of feed and water deprivation on the determination of body weight in mature beef cows. Okla. Agr. Exp. Sta. Res. Rep. P-943:211-215.
82. Vizcarra, J.A., and R.P. Wettemann. 1995. Immunization of beef heifers against GnRH prevents pregnancy. Okla. Agr. Exp. Sta. Res. Rep. P-943:206-210.
83. Vizcarra, J.A., R.P. Wettemann, and D.K. Bishop. 1994. Immunization of beef heifers against GnRH: effect of conjugation to different proteins. J. Anim. Sci. (Suppl. 2) 72:15. (Abs 53).
84. Vizcarra, J.A., and R.P. Wettemann. 1994. Immunization of beef heifers against GnRH prevents luteal activity and pregnancy. J. Anim. Sci. (Suppl. 1) 72:285. (Abs 1099).
85. Vizcarra, J.A., R.P. Wettemann, and G.L. Morgan. 1994. Influence of amplitude, frequency and duration of infused GnRH pulses on secretion of LH and FSH in beef cows. J. Anim. Sci. (Suppl. 1) 72:122. (Abs 467).
86. Yelich, J.V., R.P. Wettemann, T.T. Marston, J.A. Vizcarra, and L.J. Spicer. 1994. Effect of growth rate on growth hormone (GH), LH and IGF-I in prepuberal beef heifers. J. Anim. Sci. (Suppl 1) 72:123. (Abs 472).
87. Vizcarra, J.A., R.P. Wettemann, and D.K. Bishop. 1994. Effect of immunization of beef cattle against GnRH. Fifth annual graduate student research symposium. Oklahoma State University.
88. Vizcarra, J.A., and R.P. Wettemann. 1994. Immunization of beef heifers against gonadotropin releasing hormone: effectiveness of the protein that is conjugated to GnRH. Okla. Agr. Exp. Sta. Res. Rep. P-939:213-216.
89. Wettemann, R.P., H.A. Tucker, K.S. Lusby, D.K. Bishop, J.V. Yelich, and J.A. Vizcarra. 1994. Treatment with melatonin increases pregnancy rate of beef cattle. Okla. Agr. Exp. Sta. Res. Rep. P-939:204-208.
90. Vizcarra, J.A., R.P. Wettemann, and G.L. Morgan. 1994. Relationship between amplitude, frequency and duration of exogenous GnRH pulses and concentrations of LH and FSH in serum of the bovine. Proc. Fourth Inter. Conf. on the Control of the Onset of Puberty. p 9.
91. Vizcarra, J.A. 1994. Regulation of pulsatile secretion of gonadotropin releasing hormone (GnRH) in nutritionally anestrous beef cows. Ph.D. Dissertation, Oklahoma State University, Stillwater pp. 167.
92. Vizcarra, J.A., R.P. Wettemann, D.K. Bishop, and M.E. Payton. 1993. Evaluation of methods to determine the frequency of LH pulses in beef cattle. J. Anim. Sci. (Suppl. 1) 71:18. (Abs 66).
93. Vizcarra, J.A., and R.P. Wettemann. 1993. Relationship between body weight changes in postpuberal heifers and cessation of luteal activity. Okla. Agr. Exp. Sta. Res. Rep. P-933:351-353.
94. Vizcarra, J.A., R.P. Wettemann, D.K. Bishop, and M.P. Payton. 1993. Frequency of LH pulses in the bovine: Evaluation of different statistical procedures. 6th Annual Midwest reproductive Colloquium, Abstract #2.
95. Wettemann, R.P., H.A. Tucker, K.S. Lusby, D.K. Bishop, J.V. Yelich, and J.A. Vizcarra. 1993. Melatonin treatment of postpartum beef cows decreases the interval from calving to conception. J. Anim. Sci. (Suppl 1) 71:206. (Abs 464).
96. Ormazabal, J.J., R.P. Wettemann, J.A. Vizcarra, and D.K. Bishop. 1993. Stress, corticoids and luteinizing hormone (LH) secretion in cattle. Biol. Reprod. (Suppl 1) 48:66. (Abs 29).
97. Vizcarra, J.A., R.P. Wettemann, D. K. Bishop, and M. Payton. 1993. Evaluation of methods to determine the frequency of LH pulses in beef cattle. Fourth annual graduate student research symposium. Oklahoma State University.
98. Bishop, D.K., R.P. Wettemann, and J.A. Vizcarra. 1992. Blood metabolites in steers fed protein supplement daily or at 4 day intervals. Okla. Agr. Exp. Sta. Res. Rep. MP-136:245-250.
99. Vizcarra, J.A., R.P. Wettemann, D.K. Bishop, and R.E. Wright. 1991. Relationship between the occurrence of puberty in heifers and the cessation of luteal activity after nutritional restriction. Okla. Agr. Exp. Sta. Res. Rep. MP-134:44-47.
100. Vizcarra, J.A., R.P. Wettemann, D.K. Bishop, S. Al-Shorepy, A. Aslam, L.A. Baker, B. De Rohdas, and D.L. Wall. 1991. Effects of elevated ambient temperature on sweating rate, rectal temperature and respiration rate of heifers. Okla. Agr. Exp. Sta. Res. Rep. MP-134:40-43.
101. Vizcarra, J.A. 1991. Factors influencing reproduction of beef heifers: age at puberty, nutritional anestrus, glucose in plasma and consumption of cobalt. Master of Science Thesis. Oklahoma State University, Stillwater pp 78.
102. Vizcarra, J.A., R.P. Wettemann, D.K. Bishop, and R. Wright. 1991. Relationship between the occurrence of puberty and the cessation of luteal activity after nutritional restriction. J. Anim. Sci. (Suppl. 1) 69:41. (Abs 94).
103. Vizcarra, J.A. 1989. Some strategies in the management of beef cows. (Algunas estrategias para el manejo del rodeo de cria). La Estanzuela, Uruguay.
104. Vizcarra, J.A. 1989. Body condition score by visual observation in Hereford cows. (Condición corporal por apreciación visual en vacas Hereford). FUCREA Bulletin, CREA-Uruguay. Comunicación No. 151. p 23-28.
105. Vizcarra, J.A. 1989. Algunas estrategias para el manejo del rodeo de cria. Jornada Estrategias de Suplementación de Pasturas en Sistemas Intensivos, 1989 july 13 : La Estanzuela.
106. Sapelli, F., T. Sanguinetti, and J.A. Vizcarra. 1989. The effect of early weaning on reproductive performance of beef cattle. (Efecto del destete precoz sobre el comportamiento reproductivo en vacas de carne). Thesis: Vizcarra, JA advisor. Montevideo, Uruguay.
107. LaManna, A., A. Muñoz, and J.A. Vizcarra. 1987. The effect of early weaning on reproductive efficiency and calf growth. (Efecto del destete temporario sobre algunos parámetros reproductivos de la vaca y el crecimiento del ternero). Thesis: Vizcarra, JA advisor. Montevideo, Uruguay.
108. Mendez, J., J.A. Vizcarra, R. Orcasberro, and D. Vaz Martins. 1986. Body condition score during breeding and pregnancy rate in Hereford beef cows. (Condición corporal durante el entore y preñez en vacas Hereford). Annual Memories of the Uruguayan Hereford Breeders Society. 40^th Anniversary: p 60-61.
109. Mendez, J., J.A. Vizcarra, R. Orcasberro, and D. Vaz Martins. 1986. Body condition score during breeding and pregnancy rate in Hereford beef cows. (Condición corporal durante el entore y preñez en vacas Hereford). Revista Argentina de Producción Animal (supl. 1) 6:108. (Abs RF 19).
110. Vaz Martins, D.; Negro, C.; Ganzabal, A.; Vizcarra, J. 1984. Efecto de la carga animal sobre la producción de carne de una pastura asociada de trébol blanco: Festuca Lotus. Reunión Técnica, 7., 1984, Montevideo, Uruguay.
111. Mieres, J.M., Vizcarra, J.A. 1981. Efecto de distintos parámetros de crecimiento y características de la res en la composición, rendimiento y peso de cortes valiosos del cuarto trasero de novillos Hereford: estudio de ecuaciones de predicción de los mismos. Facultad de Agronomía. Montevideo (Uruguay).1981.119p (Thesis).