Trial duration for feed efficiency, residual feed intake and performance and carcass traits in the Brahman breed

Abstract

Brazil is one of the largest beef producers worldwide; however, it has low productivity and production costs are considered high. Feed is the main operational cost and represents more than half of expenditures. Increasing feed use efficiency for production of these animals should be a constant endeavor. Currently, residual feed intake (RFI) has become a prominent measure in selection of beef cattle, because it is considered to be a tool that identifies more efficient animals, that is animals that consume less feed but without loss in their performance. To evaluate the RFI, it is necessary to conduct feed efficiency tests that measure variables that are components in calculation of the RFI, and researchers conduct the test with a duration of 70 days beyond the adaptation period. Studies toward reducing the time of the test are being developed with the aim of maximizing the efficiency of the equipment necessary for measurement. The objective proposed in this study was to determine which would be the best period among those evaluated to be able to reduce the duration of the test for evaluating traits that make up the feed efficiency measure using electronic equipment (Intergado®) for measuring individual feed intake and evaluating the performance and carcass traits of the animals in three RFI classes: low, medium, and high. The database was composed of information on Brahman animals of the Santa Éster Farm owned by Casa Branca Agropastoril Ltda., in the municipality of Silvianópolis, MG. We used data on 93 young bulls of the Brahman breed with an average initial age of 420 days, which participated in five feed efficiency tests (test 1, 2, 3, 4, and 5). Each test had a duration of 70 days after a 15-day adaptation period. Individual electronic feeding troughs (Intergado®) were used to record information on feed intake. The RFI was calculated by multiple regression on the R software. The tests were subdivided into five periods of duration (28, 35, 42, 56, and 70 days), making adjustment for the variables for calculation of the RFI according to each period studied. The R software was used to estimate the Spearman correlation. The carcass performance and composition variables were fitted by the least squares method and compared among the RFI classes by the Tukey-Kramer test at 5% probability. The analyses of variance were carried out by the GLM procedure of SAS. Based on the results, for the RFI trait, it is possible to reduce the period of duration of the test from 70 days to 42 days, thereby favoring optimization of the equipment and reduction in management costs and making it possible to evaluate a larger number of animals in the herd. The animals that were classified as low RFI exhibited carcass fat deposition similar to a common animal, and performance variables were not compromised. Therefore, more efficient animals are a possibility for obtaining a sustainable and economically viable production system without lowering the quality of the final product.