Date of Graduation
Doctor of Philosophy in Animal Science (PhD)
Rick W. Rorie
Charles F. Rosenkrans, Jr.
Second Committee Member
Three studies were conducted to improve and incorporate reproductive management practices into beef cow-calf production. First study evaluated serial use of Estrotect estrous detection patches as a simple, cost-effective reproductive management tool to identify cyclic animals before breeding, distinguish between females conceiving to AI versus natural service, and determine seasonal pregnancy rate after bull removal. Also determined, was effectiveness of altered timing of GnRH treatment (1 d ± CIDR removal) in a modified 14-d CIDR-Select Synch protocol. When evaluated over a 4-wk period, estrous detection patches correctly (P < 0.01) identified 79% of cyclic and 86% of non-cyclic heifers. Patches were 96 and 98% accurate in identifying heifers and cows pregnant by AI, respectively, and were 76 and 87% accurate in identifying pregnant heifers and cows at the end of the breeding season (P < 0.01). Treatment with GnRH at CIDR removal reduced labor costs and animal handling without compromising estrous response (both ~63.0%) and AI pregnancy rates (~76 and 77%; P > 0.1). Second study determined if addition of PGF2alpha treatment on d 7 of a modified 14-d progesterone protocol improved estrous response in beef cows and effect of insemination timing on conception rate when using X-sorted semen. Cows were inseminated with X-sorted semen either 9 to 15, or 16 to 24 h after detected estrus. Percentage of cows exhibiting estrus was similar (76.5 and 71.2%; P = 0.33) regardless of treatment. Pregnancy rates after AI were similar (P = 0.64) at 63.3 and 66.7% for cows inseminated 9 to 15, or 16 to 24 h after estrus, respectively. Third study compared estrous response and synchrony resulting from administration of PGF2alpha on D 6 of CIDR protocol, with CIDR removal occurring concurrently (D 6) or 1 d later (D 7). Percentage of cows detected in estrus after synchronization was similar between treatments (74.0 and 71.4%, respectively; P = 0.83). However, 7 d CIDR treatment resulted in 100% of cows exhibiting estrus within a 12-h period versus 75% of 6 d treatment cows. Similar AI pregnancy rates were also observed regardless of treatment (65.0 and 60.0%, respectively; P = 0.74).
Davis, Amanda Jo, "Improving Production Efficiency of Beef Cow-Calf Operations" (2015). Theses and Dissertations. 25.