BREEDING STEERS FED VIRGINIAMYCIN IN MINERAL SUPPLEMENT IN DIFFERENT GRAZING INTENSITIES: PERFORMANCE, METABOLIC PROFILE AND NITROGEN METABOLISM

Abstract

The Brazilian beef cattle present poor productive indexes, which suggest the productive sector improved with the application of technologies to increase the efficiency of the digestive process and consequently the efficiency of the system. Thus, the use of growth promoters appears to be an alternative. Our aim is evaluate the performance, metabolic profile, nitrogen metabolism and ruminal microorganism in beef steers on pasture supplemented with mineral associated or not with virginiamycin at grazing intensities. The experiment will be realized on APTA experimental unit, Alta Mogiana Pole, Colina-SP. The treatments will be 2 x 2 factorial arrangement of treatments: mineral supplement vs. mineral supplement + virginiamycin (40 mg/100 kg LW) and two canopy height (15 an 35 cm). The experiment will be installed in 16 paddock each measuring 1 ha. Each paddock will be a replicate. Will be used continuous stocking with variable stocking rate, where 80 Nelore steers (5 steers/paddock) will be maintained permanently. Will be evaluate: forage accumulation, forage nutritive value, body weight gain, mineral supplement consumption, metabolic profile and will be evaluated in a randomized complete block design and repeated measures. The variable ruminal parameters, herbage consumption, microbial protein synthesis, efficiency of nitrogen utilization, and main ruminal microorganisms related to the fiber and protein fermentation will be analyzed in three simultaneous Latin square 4 x4 . All data will be analyzed in SAS software 9.2 (2008).