中文摘要：

为研究饲粮补充纤维分解酶与异丁酸及其混合物对断奶前后犊牛瘤胃液酶活力和纤维分解菌菌群的影响,试验选取30日龄体重[（48.5±0.3）kg]近似、发育正常的荷斯坦犊牛36头,随机分为4组,60日龄断奶,对照组哺乳/饲喂犊牛料＋苜蓿干草,纤维分解酶组（FE组）、异丁酸组（IB组）和复配组（IBFE组）分别补饲纤维分解酶1.83g/d（包含滤纸酶活力160 U和木聚糖酶酶活力4 000U）、异丁酸（99%）6g/d和二者混合物,并于45、90日龄在晨饲前采集瘤胃液,测定瘤胃发酵指标、酶活力和纤维分解菌的量。结果表明：45和90日龄与对照组相比,试验组总挥发性脂肪酸、丙酸、乙酸浓度显著提高（P〈0.05）;IB和IBFE组氨态氮浓度显著降低（P〈0.05）;FE、IB及IBFE 3组均显著增加犊牛瘤胃液羧甲基纤维素酶、滤纸酶、纤维二糖酶及木聚糖酶的活力（P〈0.05）,IBFE较其他组增幅最大;FE、IB及IBFE 3组均显著提高了犊牛瘤胃液产琥珀酸丝状杆菌、白色瘤胃球菌、黄色瘤胃球菌及溶纤维丁酸弧菌的量（P〈0.05）,IBFE组增幅最大。综合以上结果分析,6g/d异丁酸与1.83g/d纤维分解酶对瘤胃发酵有促进作用,二者混合添加效果更好。

英文摘要：

The objective of this study was to evaluate the effects of dietary fibrolytic enzymes and isobutyrate supplementation on enzyme activities and cellulolytic bacteria flora in pre-and post-weaning calves.Thirtysix healthy Holstein male calves with 30 days of age and similar body weight[（48.5±0.3）kg]were selected and allocated randomly to four groups.All calves were weaned at 60 days of age.Calves in control group were fed milk/diet for calves＋dried alfalfa hay,and those in experimental groups were supplemented with fibrolytic enzymes（160 Ufilter paper enzyme and 4 000 Uxylanase,1.83g/d,FE group）,isobutyrate（99%,6g/d,IB group）and their mixture（IBFE group）,respectively.Rumen fluid was collected in the morning before feeding at 45 and 90days of age for determining rumen fermentation indices,enzyme activities and cellulolytic bacteria amount.The results showed that at 45 and 90days of age,compared with control group,the concentrations of total volatile fatty acid,propionic acid and acetic acid in experimental groups were significantly increased（P〈0.05）;the concentration of ammonia nitrogen in IB and IBFE groups was significantly reduced（P〈0.05）;the activities of carboxymethyl cellulase,xylanase,filter paper enzyme and cellobiase in experimental groups were significantly increased（P〈0.05）,and the increasing extends were the highest in IBFE group;the amount of F.Succinogenes,R.albus,R.flavefaciens and B.fibrisolvens in experimental groups was significantly increased（P〈0.05）,and the increasing extend was the highest in IBFE group.Base on above results,6g/d isobutyric acid and 1.83g/d fibrolytic enzymes have promoting effects on rumen fermentation,and the better is their combination.