Impact of different supplementation strategies on Nellore heifers on nutritional and reproductive performance

Abstract

The Brazilian herd is composed almost entirely of Bos indicus animals, which are more adapted to the tropical climate and non-precocious. Reproductive characteristics have low heritability, showing that nutrition and the environment can influence. The objective of the project is to define the best nutritional strategy in the Nellore heifers growing to reach the body weight (BW) for attainment the puberty with 14 months. The experiment will be carried out at APTA/Colina-SP. A total of 126 weaned heifers weighing 180 kg (7-8 months) will be used. The experimental design will be in a randomized block, consisting of 18 experimental units, consisting of the paddock/pen (7 animals each), distributed in three treatments until the diagnosis of gestation of the second artificial insemination at fixed time: feedlot, fixed supplementation (10 g/kg BW) and increasing supplementation (8 to 12 g/kg BW). The pasture is composed of Brachiaria brizantha and the supplementation will be done daily at 10 h in the morning and the diet in the feedlot will be provided twice a day. Performance characteristics, grazing evaluations, body condition score, biometric measurements, and carcass and reproductive ultrasonography will be done every 42 days or at strategic heifer development points. At the start of the breeding season, a heifer from each paddock/pen will be slaughtered for determination of the gene expression of some reproduction-related genes. After the diagnosis of gestation of the second insemination, all heifers will be managed similarly and together for estrus synchronization and artificial insemination. The analysis of the data will be done using the PROC MIXED and GLIMMIX of SAS, considering a 5% probability for the type I error and the means will be compared by the tukey test.