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

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.

ACKNOWLEDGEMENTS

This work was supported by a grant from Guangdong Provincial Key Laboratory of Animal Nutrition Regulation (DWYYTK-18KF006) and Key Research and Development project of Shanxi Province (201903D221001), and Animal Husbandry Key Discipline Construction programme in ‘1331 project’ of Shanxi Province.

CONFLICT OF INTEREST

The Authors declare that there is no conflict of interest.

METADATA IN OTHER LANGUAGES:

Chinese

混合纤维酶对荷斯坦牛生产性能、营养物质消化、瘤胃发酵和瘤胃菌群的影响

关键词：纤维素酶, 微生物酶活性, 营养物质消化率, 瘤胃细菌, 木聚糖酶

摘要: 本研究旨在评价混合纤维分解酶（FEM）——纤维素酶、木聚糖酶、果胶酶和漆酶的混合物——对公牛营养物质消化和瘤胃发酵的影响。选用8头装有瘤胃瘘管的荷斯坦公牛，采用4 × 4拉丁方重复设计，随机分为4个处理组：对照组、低FEM（LFEM）、中FEM（MFEM）和高FEM（HFEM），分别添加0、0.25、0.50 和0.75 g/kg FEM。虽然添加FEM对干物质采食量和平均日增重有正线性影响，但对饲料转化效率无影响。添加FEM可线性提高营养物质的全消化道消化率，分别在0.50和0.75 g FEM/kg DM时达到最大值，瘤胃pH值和乙酸/丙酸比值均线性降低。总挥发性脂肪酸（VFA）浓度随FEM剂量的增加呈线性升高，瘤胃氨态氮含量不受影响。对于玉米青贮，瘤胃DM和有机物质的有效降解率（ED）呈二次曲线下降，MFEM组的有效降解率达到最大值，而中性洗涤纤维的有效降解率（ED）呈线性升高。添加FEM后，纤维素分解酶、α-淀粉酶和蛋白酶的活性和细菌、真菌、原生动物、琥珀酸纤维杆菌、白化瘤胃球菌、瘤胃普雷沃氏菌、溶纤维丁酸弧菌和嗜淀粉瘤胃杆菌的数量呈线性增加，但对产甲烷菌和黄瘤胃球菌的数量无影响。添加FEM后，尿嘌呤衍生物总排泄量线性增加。综上所述，混合纤维酶以0.50 g/kg DM为适宜添加量，可提高牛饲粮中营养物质的消化率和总VFA产量。

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