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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

2005; Elsevier BV; Volume: 87; Issue: 3-4 Linguagem: Inglês

10.1016/j.anireprosci.2004.12.002

1873-2232

C.S. Ahuja, Felipe Montiel, R.S. Canseco, E. Silva, Gabriela Mapes,

Effects of Environmental Stressors on Livestock

Anestrous and lactating Bos taurus by Bos indicus crossbred cows with minimum body condition were studied to determine the efficacy of GnRH + PGF2α 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 μg of GnRH on day 0 and 150 μg of PGF2α 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 (PGF2α injection) until day 12; (2) Ovsynch (n = 24), 200 μg of GnRH at 48 h after PGF2α (day 9) + timed-AI (TAI) 16–20 h later; (3) CO-Synch (n = 25), 200 μg of GnRH + TAI at 48 h after PGF2α (day 9). Control cows (n = 25) received no treatment + AI 12 h 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. Palpation per rectum and transrectal ultrasonography were used on days −30, −20, −10 and 0 to confirm anestrus (absence of CL and no signs of estrus at each evaluation) but with ovarian follicles ≥10 mm on day 0. Pregnancy rate was 0% for Select Synch, 21% for Ovsynch and 28% for CO-Synch (P < 0.05). In conclusion, the Ovsynch and CO-Synch protocols resulted in greater pregnancy rates compared with the Select Synch protocol in Bos taurus/Bos indicus cows with minimum body condition that were anestrous and lactating during the summer months in a tropical environment.