低蛋白日粮补饲过瘤胃蛋氨酸、亮氨酸及异亮氨酸对后备牛生长及消化性能的影响

Effects of Supplementation of Rumen-protected Methionine,Leucine and Isoleucine in Low-Protein Diets on Growth and Digestive Performance of Heifers

本试验旨在研究低蛋白日粮补饲过瘤胃蛋氨酸(RPMet)、过瘤胃亮氨酸(RPLeu)、过瘤胃异亮氨酸(RPIle)对7月龄后备牛生长性能、消化性能、血液生化指标及氮平衡的影响。选择平均日龄为(211.5±1.5)d、初始体重为(219.6±5.8)kg的40头健康荷斯坦后备母牛,随机分为5组,每组8头。高蛋白日粮为正对照组(HP组),日粮粗蛋白质含量14.6%;低蛋白日粮为负对照组(LP组),日粮粗蛋白质含量11.6%;低蛋白日粮+RPMet(LP+M)组;低蛋白日粮+RPIle和RPLeu(LP+IL)组;低蛋白日粮+RPMet、RPIle和RPLeu(LP+MIL)组。试验预试期10 d,正试期30 d。结果表明:HP组的平均日增重高于LP、LP+M组(0.05≤P<0.1);HP组的血清尿素含量高于LP组(P<0.01);各组间的中性洗涤纤维采食量有差异趋势(0.05≤P<0.1);HP组的摄入氮高于其余组(P<0.01),LP+IL组的摄入氮最低(P<0.01);LP组尿氮低于HP组(P<0.01)。综上,在日粮中以过瘤胃保护形式添加Met、Leu、Ile,适当降低日粮蛋白水平不影响后备牛生长性能,一定程度上提高了日粮氮转化效率。

The aim of this study was to investigate the effects of supplementation of rumen protected methionine(RPMet),leucine(RPLeu),and isoleucine(RPIle)in low-protein diets on growth and digestive performance,blood biochemical indices and nitrogen balance of 7 month-old heifer.The forty healthy Holstein heifer with average age(211.5±1.5)days and initial weight(219.6±5.8)kg were randomly divided into 5 groups with 8 heifer per group.The experimental treatment was high protein diet as a positive control group with dietary CP content 14.6%(HP);low protein diet as a negative control group with dietary CP content 11.6%(LP);low protein diet+RPMet(LP+M)group;low protein diet+RPIle and RPLeu(LP+IL)group;low protein diet+RPMet,RPIle and RPLeu(LP+MIL)group.The adjustment period lasted for 10 days and the experiment period lasted for 30 days.The results showed that the average daily gain of the HP group tended to be higher than that of the LP and LP+M groups(0.05≤P<0.1).The difference in serum urea content between groups was extremely significant(P<0.01).There was a trend of difference in the feed intake of neutral detergent fiber between groups(0.05≤P<0.1).The nitrogen intake of the HP group was significantly higher than that of other groups,and the nitrogen intake of the LP+IL group was significantly lower than that of other groups(P<0.01);urine nitrogen in the LP group was significantly lower than that in the HP group(P<0.01).In conclusion,the growth performance of the heifer was not affected when rumen protected Met,Leu,and Ile added in low-protein diet,,to a certain extent,the conversion efficiency of dietary nitrogen was improved,and the emission of fecal and urine nitrogen reduced.