日粮补充异丁酸对犊牛生长性能、瘤胃发酵和纤维分解菌菌群的影响

Effects of isobutyrate supplementation on growth performance, ruminal fermentation and cellulolytic bacterial abundance in calves

为探索异丁酸对犊牛生长性能、瘤胃发酵、纤维分解菌菌群和酶活性的影响,试验选用15日龄荷斯坦犊牛36头,随机分成4组,对照组、低水平异丁酸组(LIB)、中水平异丁酸组(MIB)和高水平异丁酸组(HIB)分别饲喂异丁酸0、3、6和9g·d^-1,预饲15d,分别于60日龄(断奶)和90日龄测定体重和采集瘤胃液进行分析。结果表明,MIB组和HIB组犊牛干物质采食量、日增重和经济效益显著高于对照组(P<0.05)。90日龄时HIB组犊牛瘤胃pH值显著低于对照组和LIB组(P<0.05)。MIB和HIB组瘤胃总挥发性脂肪酸和乙酸浓度显著高于对照组和LIB组(P<0.05);MIB和HIB组犊牛60日龄时瘤胃乙酸/丙酸显著高于对照组(P<0.05),90日龄时显著高于对照组和LIB组(P<0.05)。60和90日龄时MIB和HIB组瘤胃异丁酸均显著高于对照组(P<0.05)。60日龄时MIB和HIB组木聚糖酶和α-淀粉酶显著高于对照组(P<0.05),MIB和HIB组纤维二糖酶、果胶酶、溶纤维丁酸弧菌、黄色瘤胃球菌和产琥珀酸丝状杆菌显著高于对照组和LIB组(P<0.05);90日龄时MIB和HIB组各种瘤胃酶活力和纤维分解菌均显著高于对照组和LIB组(P<0.05)。结果显示,日粮补充异丁酸促进了犊牛瘤胃纤维素分解菌的生长,提高了纤维素分解酶的活性,进而促进了犊牛瘤胃发酵和生长发育。由于MIB与HIB之间各指标差异不显著,兼顾经济效益,在本试验条件下异丁酸的最佳添加量为6.0g·d^-1。

This study evaluated the effects of isobutyrate (IB) supplementation on growth performance,ruminal fermentation,ruminal cellulolytic bacteria abundance and ruminal enzyme activities in pre- and post-weaned dairy calves.Thirty-six Chinese Holstein male calves were randomly allocated to four groups at 15 days of age.The treatments were control,low-IB (LIB),medium-IB (MIB) and high-IB (HIB) with 0,3,6 and 9 g isobutyrate per calf per day,respectively.At 60 days of age (weaning) and 90 days of age,body weight of calves was measured and ruminal fluid was collected for analysis.The results showed that dry matter intake,average daily gain and economic benefit were higher (P<0.05) for MIB and HIB than for control in pre- and post-weaned calves.Ruminal pH was lower (P<0.05) for HIB than for LIB and control in calves at 90 days of age.Ruminal total volatile fatty acids and acetate concentrations were higher (P<0.05) for MIB and HIB than for LIB and control.The ratio of acetate to propionate was higher (P<0.05) for MIB and HIB than for control in calves at 60 days of age,and was higher (P<0.05) for MIB and HIB than for control and LIB in calves at 90 days of age.Ruminal isobutyrate concentration was higher (P<0.05) for MIB and HIB than for control in calves at 60 and 90 days of age.At 60 days of age,activities of xylanase and α-amylase were higher (P<0.05) for MIB and HIB than for control,activities of cellobiase and pectinase as well as abundance of Butyrivibrio fibrisolvens,Ruminococcus albus and Fibrobacter succinogenes were higher (P<0.05) for MIB and HIB than for control and LIB.At 90 days of age,all the ruminal enzyme activities and cellulolytic bacterial abundance values were higher (P<0.05) for MIB and HIB than for control and LIB treatments.These results indicated that isobutyrate improved growth performance and ruminal fermentation through stimulation of ruminal cellulolytic bacterial growth and enzyme activity.There was no significant difference in measured prarmeters between MIB and HIB;thus,the optimum supplementary dose of isobutyrate was found to be 6 g per calf per day under the conditions of this experiment.