Supplementation protocols for Nellore young bulls during growing phase in transitional from rainy to dry season

The scope of this research is to study the effect of the supplementation protocols and the virginiamycin (VM) during the transition from water season to drought. It was evaluated the animal performance and the ruminal parameters of the Nellore cattle kept on Brachiaria brizantha cv. Marandu pasture at the growth phase. It was evaluated two supplementation protocols: 1) Control: mineral salt and 2) Protein-Energy supplement (25% of Crude Protein) provided in the amount of 0.3% of body weight (BW). In each protocol evaluated the presence or absence of virginiamycin (40 mg of VM per 100 kg BW). For the performance, 168 young bulls at the age of twenty months and weighing 355?16.2 kg of BW were used. The animals were divided into 12 paddocks with 14 animals each (experimental unit), and distributed following the randomized block design at 2 x 2 factorial arrangement. For the ruminal parameters, 12 young bulls cannulated in the rumen were divided into 12 paddocks which resulted in three animals per treatment. The ruminal fluid was collected at 0 h (initial) and after 6, 12 and 18 h of the supplementation. The results were analyzed using PROC MIXED of SAS 9.1, and when the averages where considerable, it was used the "t" test, (P<0.10). The results showed no significant differences between the quantity of dry matter mass (P=0.31), with average of 3.000 kg/ha. Between protocols, the animals receiving protein- energy supplement showed average daily gain (ADG) and BW 32.3% and 9.1% kg higher than the animals from the control group (0.450 kg/day; 385 kg) (P=0,01), respectively. For VM, there was no difference in ADG (P=0.37), BW (P=0.31) and pH (P=0.39), average 0.530 kg/day, 406 kg and 6.5, respectively. However, the animals which received VM had ammonia nitrogen concentrations 13.6% higher. Due to the time increase after the supplement supply, the pH decreased 9.2% (P<0.01) and the ammonia nitrogen increased 1.4% up to 12 h, with 6.8 and 5.9 mg/dL of initial average. It is recommended the use of protein-energy supplement for young bulls on growing phase in pasture in the transitional period from rainy season to dry season. The use of VM did not improve the performance and ruminal parameters of the animals.