Effects of supplements containing different additives on nutritional and productive performance of beef cattle grazing tropical grass.

A grazing trial was carried out to evaluate the inclusion of three feed additives in supplements (crude protein, CP 230 g/kg dry matter, DM) on the performance, voluntary intake, and digestibility of beef heifers grazing Brachiaria decumbens (CP 81 and neutral detergent fiber, NDF 615 g/kg DM). Thirty-five Nellore heifers (21 months of age and 383 ± 6.29 kg of body weight, BW) were used in a completely randomized design. The treatments were as follows: no supplement (control); supplement fed at 1 kg/animal/day without additives (S); supplement with monensin (S + M); supplement with yeast culture (S + YC); and supplement with enzyme complex (S + EC). All of the supplemented heifers had greater (P < 0.1) average daily gain (∼0.186 kg/day) compared to the control treatment (0.014 kg/day). Average daily gain and final BW were similar (P > 0.1) among supplemented heifers. Monensin inclusion in the supplement decreased (P < 0.1) forage DM (expressed as g/kg BW) and NDF intake (expressed as kg/day and as g/kg BW). All of the feed additive inclusions decreased (P < 0.1) NDF digestibility. In conclusion, the heifers' performance was improved by concentrate supplementation. However, the inclusion of additives did not enhance this effect.