SUPLEMENTAÇÃO DE TOURINHO NELORE A PASTO, COM OU SEM ADIÇÃO DE NARASINA NO PERÍODO DE RECRIA, E TERMINAÇÃO DE CONFINAMENTO

Abstract

The objective of this study was to evaluate the performance and growth of Nelore bulls reared on pasture, with different supplements, with or without narasin during the growing season, and the effect on feedlot performance, carcass and meat quality. There were used 98 Nelore bulls, with average age of 20 months and average initial weight of 301.4 ± 30,44 kg. The animals were randomly assigned to four treatments: mineral supplementation (SM); mineral supplementation with narasin (SMN); protein-energy supplementation (SPE); and protein-energy supplementation with narasin (SPEN). The bulls were kept in a rotational grazing system, in Tifton-85 pasture, in area of 6.99 ha-1, with 12 paddocks distributed in four modules of three paddocks each. At each 21-day period, the animals were switched from modules to have no grazing effect. The animals were taken to 16 confinement stalls to receive the treatments, being placed in the same stalls every day for earrings identification, from 10:00 to 14:00 for supplement consumption, later they were returned to the respective grazing paddocks. After a supplementation period of 78 days on pasture, the animals were terminated in feedlot, where they received the same diet for a period of 90 days. In the feedlot the animals were fed twice a day with silage and concentrate, which were weighed on an electronic scale and manually mixed in the feeder. The animals were weighed at the beginning and at the end of each experimental period, together with the morphometric measurements. At the end of the feedlot, the animals were slaughtered and data related to the quantitative and qualitative evaluations of carcass and meat were collected. The data obtained in all variables were subjected to critical and consistency analysis, observing the basic premises of parametric analysis such as normality and homoscedasticity. To evaluate the treatments effect, analyzes of variance (Test F) were performed and the means were compared using the Tukey test with 0.05 level of significance. In the pasture supplementation period, the animals submitted to the SPEN treatment obtained higher weight gain, and consequently a higher average daily gain. No significant effects were observed during the feedlot termination period. With the exception of withers height, body length and chest circumference, which showed higher values for animals that received protein-energy supplementation with the narasin additioon, the other morphometric measurements did not differ between treatments. The narasin inclusion for Nellore bulls under protein-energy supplementation on pasture considerably increased the weight gain of the animals without altering the supplement consumption, indicating a better energy use from food due to the ionophores use. The same did not occur for the performance and carcass characteristics of the animals after the feedlot period in confinement.