Avaliação do emprego de GnRH ou benzoato de estradiol em novilhas sincronizadas com o sistema Crestar (Norgestomet) e prostaglandina

Abstract

One of the methods of synchronization of calves in cattle that has been shown to be quite effective is the association of progetagens implanted subcutaneously for 7 to 9 days with estradiol on the day of implantation and prostaglandin on the day of removal, which aims to perform artificial insemination (AI) at a fixed time. The efficiency of the method can be further improved with the application of estradiol benzoate 24 hours after removal of the implant. greater synchrony of the follicular waves emerging through the generation of the pulsatile pattern of LH secretion and therefore result in greater efficiency of AI at a fixed time. For this purpose, 40 crossbred heifers of approximately similar age and body condition will receive on Day 0 the subcutaneous implant of Norgestomet (CRESTAR) and an injection of 2 mg of estradiol benzoate and 50 mg of progesterone. On day 7 or 8, the implant will be removed and a dose of prostaglandin F2a will be applied. We will then divide the animals into two groups, with the first control group receiving a dose of 1 mg of estradiol benzoate 24 hours after removal of the implant and in sequence after 30 hours of this injection, the I.A. The second group of heifers, experimental, will receive a dose of GnHR (10 mg buserelin or 100 mg gonadorrelin) 36 to 48 after removal of the AI ​​implant 24 hours after this injection. The diagnosis of pregnancy will be made 34 days after the AI ​​through ultrasound examination. The insemination pregnancy rate in the synchronization period and the fixed time insemination pregnancy rate will be evaluated. For this, the animals will also be accompanied by the visual method of observation of spines.