PSVII-14 - Feeding carbohydrases to grazing beef cattle under different nutritional strategies on dry season: Ruminal fermentation

The aim with this trial was to evaluate two nutritional plans with the addition of carbohydrases enzyme blend (CEB) on ruminal fermentation of grazing Nellore bulls in dry season. Five rumen cannulated Nellore steers (BW = 350 kg) were used. Animals were randomly assigned to a treatment sequence in a 5×5 Latin square experiment with 15 d-periods (10 d to diet adaptation and 5 d for data collection), following a completely randomized design, being the treatments: mineral-proteic supplementation (Fosbovi^® Proteico 35; PS) offered at 0,1% BW (0 or 4.75 g/animal/day of CEB) or mineral-protein-energetic supplementation (Fosbovi^® Proteico-Energético 25; PES) offered at 0.3% BW (0, 4.75 or 9.50 g/animal/day of CEB). The CEB was mainly composed by beta-glucanase and xylanase enzymes (Ronozyme^® VP and Ronozyme^® WX). Both enzymes and supplements were provided by DSM Nutritional Products Brasil S.A. Rumen fluid samples were collected on the last day of each experimental period before (0), and 2, 4, 6, and 8 h after supplements were offered. Data were analyzed using PROC MIXED of SAS. Steers fed PSE had greater (P ≤ 0.041) rumen concentration of acetate, propionate, and butyrate, and lower (P = 0.028) acetate to propionate ratio in comparison with animals fed PS. Rumen acetate concentrations were 61.6 and 58.8 mmol/L and rumen propionate concentrations were 15.2 and 13.7 mmol/L for animals under the PSE and PS, respectively. A quadratic effect (P = 0.048) for carbohydrases enzyme blend was observed in NH₃-N ruminal concentration of PES animals, where 4.75 g/day level presented the lower concentrations compared to control (24.13 vs. 32.20 mg/dL). Furthermore, rumen concentrations of acetate (P = 0.002) and propionate (P = 0.021) linearly increased with enzymes inclusion for PSE plan. PSE nutritional strategy positively influence ruminal fermentation of Nellore steers in dry season and its effects can be enhanced with CEB inclusion of 4.75 g/day.