Brito et al., 2008. Rev. Bras. Zootec., 37 (9): 1641-1649

The effects of concentrate supplementation to young bulls kept in Brachiaria brizantha [Urochloa brizantha] cv. Marandu pastures during the dry season of the year was evaluated. 16 young Canchim bulls (7 months old, 250 kg body weight) were allotted to a completely randomized design in 2*1 factorial arrangement. The factors consisted of balanced supplements for two potential of microbial fermentations: 9.5 and 11.0 g microbial crude protein/MJ fermentable metabolizable energy and for weight gain of 0.5 and 1.0 kg/day. The animals were individually supplemented daily for 168 days after 21 days of adaptation. The daily intake of forage was estimated in 5.91 kg dry matter/animal. The supplementation for 0.5 kg/day of weight gain provided gains and feed conversion of 0.94 kg/day and 1.08 kg supplement/kg of gain, respectively, lower than the results obtained to the weight gain of 1.0 kg/day (1.09 kg/day and 3.18 kg supplement/kg gain, respectively). There was no effect of the fermentation potential on weight gain, feed conversion and ribeye area, but the final backfat thickness increased with the higher potential fermentation. Supplementation for 0.5 kg/day weight gain showed a better economic outcome, but did not achieve appropriate slaughter weight. The supplementation with concentrate formulated to increase the efficiency of rumen microbial protein synthesis reduced the profitability of the system.