Efeito do escore de condição corporal no escore de ovário e na taxa de prenhez de vacas Nelore inseminadas em tempo fixo

Abstract

Reproductive performance is one of the most relevant economic factors in a cattle herd and is greatly influenced by the body condition score (BCS), which has a great influence on the potential that a cow has to get pregnant. This study aimed to evaluate the effect of body condition score, at the beginning of the fixed-time insemination protocol (FTAI), on ovary score and pregnancy rate in Nellore females. The experiment was carried out using data of 1.790 females, being heifers (n = 586), primiparous (n = 421) and multiparous (n = 786), managed on ten commercial farms located in the states of Minas Gerais, Mato Grosso do Sul and Rio de Janeiro. The body condition score (BCS) and ovarian score evaluations were performed at the beginning of protocol (D0). The BCS was evaluated on a scale from 1 to 9. In the ovaries, the presence of follicles and corpus luteum was evaluated. The FTAI protocol, based on estrogen and progesterone, started 30 days after the birth of the last calf of each batch and the cows were inseminated with semen from bulls of the Angus, Nellore, Charolais and Brangus breeds. Pregnancy diagnosis was performed 30 days after FTAI. Data were analyzed by logistic regression and analysis of variance, using the Minitab program, including data on the effects of the BCS, animal category, as well as possible interactions in the model. Statistical significance was established as P ≤ 0.05 and statistical trend as 0.05 < P ≤ 0.10. The animal category influenced the BCS, ovarian score and pregnancy by FTAI (P ≤ 0.05). No effect of BCS was detected on the pregnancy rate by FTAI of multiparous cows (P > 0.05), but in primiparous cows a trend (P = 0.063) and an effect in heifers (P < 0.05) were detected. Primiparous cows and heifers with better BCS showed greater pregnancy by FTAI. An effect of BCS (P < 0.05) was detected on the ovary score in the three categories evaluated, and females with the best BCS (≥ 6.50) also had better ovary scores. It is concluded that the body condition score influences the ovarian score in all categories analyzed and the pregnancy rate in primiparous and heifers. These results show the importance of good nutritional management to maintain females with adequate body condition at the beginning of the FTAI program.