Pregnancy rate following GnRH + PGF 2alpha 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 2alpha 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 microg of GnRH on day 0 and 150 microg of PGF 2alpha 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 2alpha injection) until day 12; (2) Ovsynch (n = 24), 200 microg of GnRH at 48 h after PGF 2alpha (day 9) + timed-AI (TAI) 16-20 h later; (3) CO-Synch (n = 25), 200 microg of GnRH + TAI at 48 h after PGF 2alpha (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 > or = 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.
Ahuja
C
C
Departamento de Reproducción, Facultad de Medicina Veterinaria y Zootecnia, Universidad Veracruzana, Circunvalación S/N Esquina Yañez, C.P. 91710, Veracruz, Ver. México.
Montiel
F
F
Canseco
R
R
Silva
E
E
Mapes
G
G
D000780:Anestrus / Q000502:physiology; D000818:Animals; D002417:Cattle / Q000502:physiology*; D003433:Crosses, Genetic; D015237:Dinoprost / Q000008:administration & dosage*; D004973:Estrus Synchronization / Q000379:methods*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage*; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation; D016015:Logistic Models; D008297:Male; D008800:Mexico; D011247:Pregnancy; D018873:Pregnancy Rate; D014329:Tropical Climate
D007987:Gonadotropin-Releasing Hormone; D015237:Dinoprost