Induction of ovulation with GnRH and PGF2alpha in lactating Bos taurus x Bos indicus cows.
Induction of ovulation for timed artificial insemination (TAI) with the Ovsynch protocol was evaluated in 49 anoestrous and lactating Bos taurus x Bos indicus cows. Palpation per rectum and transrectal ultrasonography were used on Days -30, -20, -10 and 0 (start of treatment) to confirm anoestrus but with the presence of follicles > or = 10 mm, and every other day during treatment to determine ovarian activity. Cows were randomly assigned to: (1) Ovsynch (n = 24; Day 0, 200 microg GnRH; Day 7, 150 microg PGF2alpha; Day 9, 200 microg GnRH + TAI 16 to 20 h later) and (2) control (n = 25; no treatment). Rates of ovulation for the first GnRH injection, detection of a corpus luteum (CL) at PGF2alpha injection, pregnancy and induction of cyclicity were greater (P < 0.05) with Ovsynch. There was no effect of body condition score (P > 0.05). In conclusion, the Ovsynch protocol was not effective in obtaining acceptable pregnancy rate for TAI, but it was effective for induction of cyclicity in anoestrous and lactating Bos taurus x Bos indicus cows under tropical conditions.
Ahuja
C
C
Department of Reproduction, Faculty of Veterinary Medicine, University of Veracruz, Circunvalación S/N Esquina Yañez, Código Postal 91740 Veracruz, Ver., Mexico.
Montiel
F
F
D000818:Animals; D002417:Cattle / Q000235:genetics / Q000502:physiology*; D003008:Cloprostenol / Q000627:therapeutic use*; D003433:Crosses, Genetic; D004971:Estrus / Q000187:drug effects; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000627:therapeutic use*; D007315:Insemination, Artificial / Q000379:methods / Q000662:veterinary; D007774:Lactation; D010062:Ovulation Induction / Q000379:methods / Q000662:veterinary*; D011247:Pregnancy; D012098:Reproduction / Q000187:drug effects / Q000502:physiology
D007987:Gonadotropin-Releasing Hormone; D003008:Cloprostenol