Abstract
Pasture-based beef cattle production systems aim to maximize the interaction between forage and supplements to increase activity. In addition, supplementation and the use of food additives help optimize production efficiency and improve the use of additional nutrients. The aim of this study was to evaluate the effects of the use of additives in protein-energy supplements (PESs) on the intake, digestibility, and ruminal parameters of beef cattle raised on pasture in the rearing phase. Five male cattle were allocated to a 5 × 5 Latin square design, with five experimental periods and five treatments. The animals were kept under continuous grazing in individual paddocks of marandu palisadegrass (Urochloa brizantha cv. Marandu). The treatments consisted of a mineral mixture (MM) (0.080 kg/animal/day), PES (4.0 kg/animal/day), PES with monensin sodium (120 mg/animal/day), PES with functional oil (2500 mg/animal/day) and PES with active yeast (4000 mg/animal/day). PESs increased the total dry matter intake (DMI) (kg/day) and the DMI in terms of % body weight (%BW) and increased the intake of crude protein (CP) and the dry matter intake of digestible organic matter (DOM). The use of additives did not affect nutrient intake or digestibility. Compared with MM, the PES increased the concentrations of ruminal ammonia nitrogen and serum urea nitrogen. In addition, there was an increase in fecal nitrogen, retained nitrogen, microbial nitrogen synthesis and microbial efficiency. The use of monensin sodium, functional oil and active yeast in protein-energy supplements for beef cattle in pastures did not affect the nutritional parameters under the conditions observed in this study.