Fetal programming, feed efficiency and productive traits in Nellore cows in extensive production systems

Abstract

The evaluation of the phenotypic variation of economic interest traits of cows in beef herds is essential to increase knowledge about the impact of this animal category on the production system as a whole, and to improve the efficiency of cattle herds in the country. The present project will be developed with the objective of identifying and quantifying the phenotypic variation of productive, reproductive and feed efficiency characteristics of Nellore cows in extensive and semi-intensive production systems, in order to correlate them to the productive characteristics of their progenies. Productive and reproductive data will be used from the cows of the Selection Program for Post-weaning Weight of the Instituto de Zootecnia, collected since 1981 in extensive production systems, under reproductive management of natural breeding, and more recent information from the same herds, collected from 2020, under fixed-time artificial insemination (FTAI) reproductive managements in semi-intensive production systems. This information will be used to determine the associations between body weight, age at puberty and at first conception, and feed efficiency of cows; and growth, skeletal size, and body composition (obtained by ultrasound) of calves (from birth to weaning), in addition to endocrine, energy, protein, and mineral metabolism through metabolic indicators. The results generated will be important to promote the evaluation, selection and use of more efficient animals, in production systems better designed for meat production.