Exogenous enzyme supplementation for beef cattle under different nutritional strategies during the rainy season: Performance and Metabolism

Abstract

This study aimed to evaluate the performance and metabolism of beef cattle in grazing systems under different nutritional strategies with enzyme supplementation. The experiment was carried out at the DSM Experimental Center in Rio Brilhante, MS, Brazil. Experiment 1 used one hundred and two Nellore steers with an average body weight (BW±SD) of 320±0.18 kg, were distributed in a completely randomized design with a 2 × 3 factorial arrangement. Experiment 2 used five Nellore steers rumen cannulated steers with an average (BW±SD) of 350±0.18 kg and randomly distributed in a 5 × 5 Latin square with periods of 21 days. The treatments consisted: 1) supplementation strategy (protein supplement (PRO) at 0.1 % BW or protein-energy (PPE) supplement at 0.3 % BW); and 2) increasing levels of a mixture of exogenous enzymes [0 g of enzymes; 1 g/d Ronozyme WX (xylanase) and 3.75 g/d Ronozyme VP (beta-glucanase, pectinase and hemicellulose); and 2 g/d Ronozyme WX and 7.5 g/d Ronozyme VP. Experiment 1: Nutritional plans significantly influenced final weight, average daily gain, and supplement intake. Steers receiving the PPE supplement showed superior performance, with an average final weight of 432.63 kg compared to 390.21 kg for PRO. A quadratic effect was observed for final weight and average daily gain in animals on the PPE diet, with the maximum predicted enzyme level being 4.60 g/day. PRO animals showed a linear increase in growth with enzyme inclusion, achieving 0.881 kg/day weight gain. Experiment 2: Steers on the PPE nutritional plan showed higher supplement and crude protein intake compared to those on the PRO. The addition of a carbohydrase enzyme blends enhanced pasture, dry matter and crude protein intake. Digestibility of dry matter, crude protein, and NDF was significantly higher for animals on the PPE. Steers receiving the PPE also showed higher ammoniacal nitrogen concentration, ruminal pH, and acetate levels, with a quadratic effect on butyrate concentration and linear effects on several ruminal parameters. Both nutritional plans, combined with carbohydrase enzymes, significantly improved performance in Nellore steers during the rainy season in central Brazil, enhancing final weight and average daily gain (ADG). Enzyme supplementation optimized ruminal fiber degradation and nutrient digestion, with 4.75 g/day yielding the best results for PPE. For PRO, a linear increase in enzyme levels up to 9.5 g/day improved NDF digestibility and performance.