Sincronization of ovulation utilizing the Crestar® protocol associated with estradiol benzoate, PGF2±, PMSG and GnRH in beef cows
Keywords:Estrous cycle, Beef cows, Cows, Applied reproduction animal, Ovulation
AbstractThe objective of this study was to evaluate the effects of ovulation using PMSG, GnRH, Estradiol Benzoate and PGF2a in combination with Crestar? protocol and AI at fixed time. Three hundred forty eight multiparous cows, crossbreed Nelore (Bos taurus indicus) X Charolais (Bos taurus taurus) were divided in two groups: 179 suckling cows and 169 non-suckling cows. Those cows received a Crestar® protocol for follicular growth synchronization consisting of a subcutaneous implant with 3mg of norgestomet and 3mg of norgestomet plus 5mg of estradiol valerate injection (day of implant insert). The implant was removed after nine days. Cows were submitted to five treatments for pharmacological control of ovulation and were artificially inseminated at fixed time: T1 - (n=70): injection of physiological solution 48h after implant removal (D 12); T2 - (n=68): 0.75mg of estradiol benzoate 24h after implant removal (D 11); T3 - (n=70): 150mg of PGF2a at same day of implant removal (D 9) and 0.75mg of estradiol benzoate 24h after implant removal (D 11); T4 - (n=70): the cows received 500 UI of PMSG at implant removal (D 10) and T5 - (n=70): cows received 500mg of GnRH 48h after implant removal (D 12). Those cows were artificially inseminated 54-56h after implant removal. Pregnancy rate was analyzed by logistical regression program. There were no differences among treatments (P>;0.05) 35.7, 31.4, 22.0, 37.0 and 42.8% for T1, T2, T3, T4 and T5, respectively.
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