Influence of fibrolytic enzymes mixture on performance, nutrient digestion, rumen fermentation and microbiota in Holstein bulls

Abstract

The aim of the study was to evaluate the influences of fibrolytic enzymes mixture (FEM) - a mixture of cellulase, xylanase, pectinase and laccase - on nutrient digestion and ruminal fermentation in bulls. Eight Holstein bulls fitted with rumen cannula were used in a replicated 4 × 4 Latin square design and allocated to four treatment groups: control, low-FEM (LFEM), medium-FEM (MFEM) and high-FEM (HFEM) with 0, 0.25, 0.50 and 0.75 g/kg FEM, respectively. Even though the addition of FEM had a positive linear impact on dry matter (DM) intake and average daily gain, it had no influence on feed conversion ratio. Supplemented FEM linearly promoted nutrients total-tract digestibility, reaching greater values at 0.50 and 0.75 g FEM/kg DM. Rumen pH value and the ratio of acetate to propionate were reduced linearly, the concentration of total volatile fatty acids (VFA) elevated linearly but the content of ammonia-N was not influenced with increasing dose of FEM. For corn silage rumen degradation, effective degradability (ED) of DM and organic matter were quadratically reduced, reaching greater values in MFEM, whereas ED of neutral detergent fibre was linearly elevated. Supplemented FEM linearly increased activities of cellulolytic enzymes, α-amylase and protease and populations of bacteria, fungi, protozoa, Fibrobacter succinogenes, Ruminococcus albus, Prevotella ruminicola, Butyrivibrio fibrisolvens and Ruminobacter amylophilus, but had no impact on populations of methanogens and Ruminococcus flavefaciens. Supplemented FEM linearly increased urinary total purine derivative excretion. So, it was indicated that FEM enhanced nutrient digestibility and total VFA production, the optimum dose was 0.50 g/kg DM in bull diets.