Email: yelich@animal.ufl.edu

Research focus is on the application of the advanced research technologies to enhance and optimize reproductive efficiency in cattle of Bos indicus breeding in sub-tropical environments. The primary thrust of my research program concentrates on the manipulation of follicular development and control of ovulation to maximize the effectiveness of estrous synchronization and timed artificial insemination. However, endocrine function and communication between the hypothalamic-pituitary-ovarian axis in cattle of Bos indicus breeding is poorly understood. Therefore, preliminary models are being established to examine the hormonal control of this axis utilizing exogenous progesterone and estrogen to develop an improved understanding of the hypothalamic-pituitary responsiveness to these steroids and eventual control of ovarian function. Supplementary research is being conducted to determine if breed type and season influence the endocrine mechanisms associated with the expression of behavioral estrus and ovulation.

A minor research area is focusing in the regulation of meat quality. Through the utilization of molecular genetic techniques, we are using existing Quantitative Trait Loci to assist in identifying superior sires in the Brahman breed for marbling, palatability and tenderness. Moreover, the gene expression of key enzymes of the calpain/calpastatin system is also being investigated. The calpain/calpastatin system has been implicated in regulating postmortem tenderization of meat.

Representative Publications:

Lemaster JW, Yelich JV, Kempfer JR, Fullenwider JK, Barnett CL, Fanning MD, Selph JF. Effectiveness of GnRH plus prostaglandin F_2a for estrus synchronization in cattle of Bos indicus breeding. J Anim Sci 2001; 79:309-316.

Lucy MC, Billings HJ, Butler WR, Ehnis LR, Fields MJ, Kesler DJ, Kinder JE, Mattos RC, Short RE, Thatcher WW, Wettemann RP, Yelich JV, Hafs HD. Efficacy of an intravaginal progesterone insert and an injection of PGF_2a for synchronizing estrus and shortening the interval to pregnancy in postpartum beef cows, peri-pubertal heifers, and dairy heifers. J Anim Sci 2001; 79:982-995.

Williams de Araujo J, Borgwardt RE, Sween ML, Yelich JV, Price EO. Incidence of repeat breeding among Angus bulls (Bos taurus) differing in sexual performance. Appl Anim Behav Sci Appl Anim Behav Sci 2002; 81:89-98.

Landaeta-Hernández, AJ, Yelich JV, Lemaster JW, Tran T, Fields MJ, Chase CC Jr, Rae DO, Chenoweth PJ. Environmental, genetic, and social factors affecting the expression of estrus in beef cows. Theriogenology 2002; 57:1357-1370.

Hiers EA, Barthle CR, Dahms MKV, Portillo GE, Bridges GA, Rae DO, Thatcher WW, Yelich JV. Synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F_2a in combination with melengestrol acetate. J Anim Sci 2003; 81:830-835.