Pregnancy rate following GnRH+PGF2α treatment of low body condition, anestrous Bos taurus by Bos indicus crossbred cows during the summer months in a tropical environment

Anestrous and lactating Bos taurus by Bos indicus crossbred cows with minimum body condition were studied to determine the efficacy of GnRH+PGF(2 alpha) combinations for induction of estrus and/or ovulation on pregnancy rate during the months of the year when temperatures are greater. On day 0 (start of treatment), cows were assigned randomly to either treatment or control groups. Treated cows (n=74) received i.m. 200 mu g of GnRH on day 0 and 150 mu g of PGFZa 7 days later (day 7). On day 7, treated cows were equally distributed to each of three protocols: (1) Select Synch (n=25), artificial insemination (AI) 12 h after exhibiting estrus from day 7 (PGF(2 alpha) injection) until day 12; (2) Ovsynch (n = 24), 200 mu g of GnRH at 48 h after PGF(2 alpha) (day 9) + timed-AI (TAI) 16-20 h later; (3) CO-Synch (n = 25), 200 mu g of GnRH + TAI at 48 h after PGF(2 alpha) (day 9). Control cows (n = 25) received no treatment+AI 12h after exhibiting estrus from days 0 to 12. Detection of estrus was performed daily during the early morning and evening hours from days 0 to 7 in all the cows, and from days 7 to 12 in the cows treated with Select Synch and in the control group, with the aid of a sterilized bull.