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

Supplementation of fibrolytic enzymes (FE) into ruminant diets had been used as a nutritional strategy to improve performance via enhancing nutrient digestion (Beauchemin et al., 2004). It was previously demonstrated that supplementation with a mixture of xylanase and cellulase enhanced performance and nutrient digestibility in steers (Gómez-Vázquez et al., 2011) or cows (Yang et al., 2000). However, other researchers observed that average daily gain (ADG) and feed conversion ratio (FCR) were unchanged with supplementing xylanase and cellulase mixture (Krueger et al., 2008). The divergent responses should be related to the differences in activities and formulations of enzymes used in these studies. Eun et al. (2007) demonstrated that the optimum dose proportions and activities of supplied FE were critical for the magnitude of the improvement in forage utilization. The factors limiting the digestion of dietary fibre by rumen microbes were some plant cell wall 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. Received: 27 October 2021 Revised: 19 February 2022 Accepted: 7 March 2022