Fatores que afetam a taxa de gestação ao final da estação de monta de novilhas Nelore manejadas a pasto

Abstract

In beef cattle, the production of calves during the calf phase is the basis of the entire production cycle, where reproduction is considered the determining factor for achieving success in animal production. When it comes to reproductive precocity there is a great impasse found in Brazil, the average age at the first birth of pasture-raised Nellore females is 36 months, which negatively affects the reproductive efficiency of the herd and the genetic advancement of the breed. The reproductive efficiency of a herd is determined by the ability to impregnate cows in a timely manner, that is, the sooner the females become pregnant, the better. The objective of this work was to evaluate the reproductive efficiency of Nellore heifers, at the Capim Branco Experimental Farm of the Federal University of Uberlândia, managed on pasture in the last 3 years. The heifers were submitted to a 4-month breeding season (December to March) and treated with FTAI protocol. Pregnancy diagnosis was performed 30 to 35 days after FTAI by ultrasonography and pregnancy was confirmed 60 days after the end of the breeding season. The highest pregnancy rate obtained was in the 2022/2023 breeding season, where the average age at the beginning of the season was 730 days, compared to other seasons, a better result for older females. It is concluded that the reproductive efficiency of Nellore heifers is directly related to the age at which they are exposed to reproductive management, resulting in better pregnancy rates for females older than 24 months.