Hormonal and Pregnancy Rate of Nelore Cows Artificially Inseminated at a Fixed Time (AIFT) Associating Melengestrol Acetate, Gonadorelin and Prostaglandin
Jose Eduardo Jardim Murta, Venício Jose de Andrade, Vicente Ribeiro do Vale Filho

Abstract
Pregnancy rates and follicular diameter of Nellore cows submitted to AIFT were evaluated in two groups: In G1, n = 30 (dose of 100 mg gonadorelin on day one - d1; 75 mg D-cloprostenol on day seven - d7, and a second dose of gonadorelin on day nine - d9); in G2, n = 30 it was applied treatment similar to G1, plus 0.05 mg MGA / cow / day, in the mineral supplement, from d1 to d7. Mean follicular diameter, by ultrasonic measures, on d7 and d9 were, respectively, 0.94 ± 0.32 and 1.09 ± 0.30 cm in cows not pregnant; and 1.14 ± 0.35 and 1.32 ± 0.27 cm (P>0,01) in those pregnant. Pregnancy rates registered after AIFT were 26.6% and 26.6% and after using roundup bulls 86.36% and 81.81%, respectively, for G1 and G2 (P>0.05). The mean MGA serum concentration was 0.12 ± 0.20 ng/mL in animals that received MGA (G1, n = 8) and did not differ (P>0.05) from the control group (G2, n = 8). It was concluded that treatment with MGA associated or not with GnRH and Prostaglandin analogues does not affect the follicular diameter mean neither the gestation rate of Nellore cows.

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