Analysis of records of embryo production in Red Brahman cows

Records of embryo production in Red Brahman donor cows (n=50) and F1 recipients (n=531) were evaluated from the collection day to the birth of the embryo produced. The effects of the sire of the donor and the embryo, protocol, season-protocol, and body condition of the donor on the total number of good, degenerated, unfertilized, and total embryos were evaluated. The number of donors collected for protocols 1, 2, and 3 were 50, 39, and 46 respectively. The production of good transferable embryos, and embryos/collection for protocols 1, 2, and 3 were 171 (4.6), 152 (4.6), and 208 (6.3) respectively. The final status of each recipient was recorded as non-pregnant, resorption, abortion, and live calf. The model used to analyze pregnancy state was: protocol, embryo stage, embryo quality, corpora lutea size, and season. The effects of sire of the embryo, season-protocol, protocol, embryo stage, embryo quality, body condition score, and corpora lutea size on gestation length and birth weight were analyzed. Season-protocol affected (P<0.05) the number of degenerated embryos. Mean number of degenerated embryos were higher (P<0.05) during winter for protocols 2 and 3 than during other seasons. The ratio for good embryos differed (P<0.01) by sire of donor. The final status of recipients was affected (P<0.01) by protocol. The maximum percentage of live calves and the minimum percentage of non-pregnant recipients were achieved for protocol 3. Gestation length differed (P<0.01) by sire of the embryo, season-protocol, protocol, and body condition score. Spring-protocol 3 resulted in the shortest while Fall-protocol 2 resulted in the longest mean gestation length. Calf birth weight differed (P<0.05) by season-protocol and by embryo quality. The lightest birth weights resulted from embryo quality grade 2 and from spring-protocol 3. These results indicate that using protocols that combine 17??-estradiol, FSH and GnRH (protocol 3) during the spring in conjunction with selection for sire of donor can increase embryo production by Red Brahman cows. Use of protocol 3 with donors in the spring, selection of embryo sire for short gestation length and transfer of quality grade 2 embryos can be used to minimize the incidence of dystocia in recipients.