Evaluation of seminal characteristics in Nellore bulls selected for residual feed intake and supplemented with polyunsaturated fatty acids in pasture conditions

Abstract

Feed efficiency is very important for breeding programs. The residual feed intake (RFI) is an indicator that has a correction of dietary intake for animal weight and weight gain. In addition, puberty is important for the improvement of breeding cattle. The production and semen quality are influenced by several factors, especially nutrition. Polyunsaturated fatty acids (PUFA) have effects on the reproductive performance of males, but few studies have been conducted to assess the impact of genetic selection for feed efficiency in reproducing the Zebu. Addressed within the context, the aim of this work is to evaluate the effects of supplementation with PUFA on pasture at puberty and in the seminal characteristics of Nelore bulls selected for RFI. It will be selected 56 young bulls of 12 months of traditional herd from the Animal Science Institute of Sertãozinho, SP. The experimental design will be completely randomized in a factorial 2 x 2 (RFI x supplementation), being high RFI with or without supplementation with PUFA, and low RFI with or without supplementation with PUFA. The experimental diets will be isoproteic and isoenergetic. The animals will be kept in Brachiaria brizantha cv. Marandu pasture in continuous stocking during the experimental period. The measurement of scrotal circumference, testicular ultrasound and semen collection to verify the seminal characteristics will be taken every each 28 days and sperm cryopreservation will be held in the last three collections. After thawing, it will be performed new tests of sperm quality. In addition, we will analyze the weight, body condition score (BCS), hormonal and plasmatic metabolics every each 28 days. The evaluation of the ultrasound carcass and individual food consumption of pasture and ration will be taken every three months in the summer, fall, winter and spring, using indicators like chromium oxide, titanium dioxide and NDFi. (AU)