The objective ofthis experiment was to study the effects of different levels of supplementationon the performance, intake, digestibility, pH and rumen ammonia concentrationin growing bulls grazing Brachiaria decumbens Stapf. pasture, duringthe dry-rainy transition season. For evaluation of performance, intake and digestibility,it was used 25 non-castrated steers at 11 months of age and initial averagebody weight of 270 kg, grouped in five plots of five animals each, followinga completely randomized design. Each plot received one of the following feedingtreatments: mineral mixture and supplement at the proportion of 0.5, 1.0, 1.5and 2.0 kg/animal/day, corresponding to 0.18, 0.36, 0.54 and 0.72% of the averagebody weight of the animals. The area designated for the animals was constitutedof five 2.0-ha paddocks. For the evaluation of the pH and rumen ammonia concentration,five crossbred non-castrated steers were used, with average body weight of 240kg, fistulated in the esophagus, rumen and abomasum, disposed in a 5 ×5 Latin square, with five treatments and five experimental periods. Animal performancebehaved in a positive linear manner according to the supplementation levels,responding with an increase of more than 80% on weight gains of the animals.Intakes of total and pasture dry matter (DM), organic matter and neutral detergentfiber were not influenced by supplementation. Intakes of crude protein, non-fibrouscarbohydrates, ether extract and total digestible nutrients as well as nutrientdigestibility and rumen ammonia concentration showed a positive linear patternin response to supplementation levels. Increasing levels of concentrate supplementationinfluence positively the performance of bulls growing on pastures during thedry-rainy transition season.
