Fatores que afetam a eficiência do protocolo de IATF com pré-sincronização, utilizando progesterona injetável de longa ação, em vacas leiteiras mestiças

Abstract

Reproductive efficiency is crucial for the productivity of dairy farm. Assessing the factors that influence the results of fixed-time artificial insemination (FTAI) protocols is important to optimize fertility programs and improve pregnancy rate and therefore, productivity. The objective was to evaluate the factors that affect the efficiency of the FTAI protocol with pre-synchronization, using injectable long-acting progesterone (P4), in crossbred dairy cows. Cows (n = 763), from a commercial farm, with more than 22 days postpartum were evaluated and those considered eligible were treated with the following hormonal protocol: On day D -10, 300 mg of injectable P4 was administered, D0 an intravaginal device of 1.2g of P4 was inserted, 2 mg of estradiol benzoate and 0.2 mg of gonadorelin was administered, on D7 0.53 mg of cloprostenol sodium was injected, on D9 the device of P4 was removed, and 1 mg of estradiol cypionate, 400 IU of equine chorionic gonadotropin and 0.53 mg of sodium cloprostenol was injected, on D11 0.2 mg of gonadorelin was administered and the FTAI was performed. At the beginning of the FTAI protocol, the following data were collected: milk production, racial composition, parity, calving and FTAI date. The pregnancy diagnosis was performed 30 days after the FTAI and reconfirmed at 45 days. Factors that affect the FTAI pregnancy/AI were analyzed by logistic regression at MINITAB program. Statistical significance was defined as P ≤ 0.05 and tendency as 0.05 > P > 0.10. Breed composition affected pregnancy/AI, cows < ¾ were more likely to become pregnant at both 30 (53.40% versus 45.63%) and 45 (52.72% versus 42.86%) days compared to cows ≥ ¾. A tendency of lactation order to affect pregnancy/AI was detected only at 45 days of gestation, multiparous cows had higher pregnancy/AI (52.75% versus 44.75%) than primiparous and second-biparous cows. No effect of the other factors analyzed on pregnancy/AI was detected. It is concluded that racial composition affects pregnancy/AI both at 30 and 45 days of gestation, and the parity trends to affect pregnancy/AI at 45 days of gestation.