Relationship between residual feed intake and sexual precocity of Nellore heifers mated at 12-14 months of age

• Grant number: 21/14492-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2022
• End date: March 31, 2023
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Guilherme de Paula Nogueira
• Grantee: José Luiz Severo da Silva
• Host Institution: Faculdade de Medicina Veterinária (FMVA). Universidade Estadual Paulista (UNESP). Campus de Araçatuba. Araçatuba , SP, Brazil

Abstract

Nutritional, growth, physiological, and genetic factors will be monitored in order to determine the relationship between carcass finishing, the residual feed intake (CAR) estimation equations, and sexual precocity in Nellore heifers. The experiment will be carried out in three locations: at the Faculty of Veterinary Medicine of Araçatuba (FMVA) UNESP, with hormonal quantification, at the Animal Development Center -Embrapa (CDA), with more intensive experimental control and measurement of variables, and in a farm of selected partner. The CAR tests will be carried out between July and October and then the FTAI protocols will start, with the pregnancy diagnosis in February. For this 70 Nellore PO heifers from the BRGN herd at Embrapa Cerrados will be evaluated, with genetic - genomic evaluation, already with weight measurements at birth, at 120 days, and at weaning, obtained from the origin of the animals. The nutritional plan to which the animals will be submitted at each stage of growth and season of the year will be determined. At the partner farm, data on weights and previous feeding, CAR values, and performance in the test and pregnancy in the 1st and 2nd FTAI will be obtained. In the experimental period, morphometric measurements, body condition scores, carcass, and reproductive tract ultrasound will be obtained at the beginning and end of the test, DNA collection for genomics, and blood for IGF-1 and NEFA. The animals will be divided into three treatments according to the CAR values, with a mean ± 0.5 SD, in which analysis of variance with tests of covariance for farm, age, and weight will be performed, correlating growth and reproduction rates using analysis of multivariate. The results may provide information and parameters that favor early reproduction in zebu herds.(AU)