日粮尿素添加水平对秦川肉牛瘤胃发酵性能的影响

摘要

为研究秦川牛肉用补饲尿素(非蛋白氮)对瘤胃发酵环境的影响,试验选用3头饲养条件一致且装有瘤胃瘘管的秦川肉牛(公牛),正常饲粮预饲25 d,随后每25 d为一个饲养阶段,每个饲养阶段逐步对其日粮添加不同水平尿素0％(干物质百分比,对照组)、0.5％(A组)、1.0％(B组)、1.5％(C组)和2.0％(D组),每个饲养阶段中每5d采集一次瘤胃液,检测分析pH、氨态氮、微生物蛋白以及挥发性脂肪酸等瘤胃发酵关键参数.结果表明,随着尿素添加水平的提高,瘤胃液pH先下降后上升,B组pH最低,与其余各组差异显著(P＜0.05);随着尿素添加水平的提高,各处理组(除D组外)总挥发性脂肪酸量均显著高于对照组(P＜0.05),其中B组最高,与其余处理组差异显著(P＜0.05).A组和B组挥发性脂肪酸与对照组均差异显著(P＜0.05),两处理组之间除总挥发性脂肪酸(TVFA)差异显著外(P＜0.05),其余四项挥发性脂肪酸指标均差异不显著(P＞0.05);随尿素添加水平的提高,四个处理组NH3-N含量均显著高于对照组(P＜0.05),其中D组显著高于其他处理组(P＜0.05);随着尿素添加水平的提高,微生物蛋白量除D组与对照组差异不显著(P＞0.05)外,其余三个处理组均高于对照组,B组最高,与其余处理组差异显著(P＜0.05).秦川肉牛日粮中添加尿素可以有效提高瘤胃氨态氮、微生物蛋白、乙酸、丙酸等,且日粮中添加量1％(干物质百分比)为最适安全添加量,可提高秦川肉牛饲养效率,降低饲养成本.%To research the effect of urea (non protein nitrogen) supplement on rumen fermentation environment for Qinchuan beef cattle,three Qinchuan bulls,with rumen fistula,were fed the diet supplied with different urea level,in five treatment stages.Before the treatment,there was a 25-day's preliminary feeding period,in which every bull was fed with normal diet.Then,urea was added in normal diet,at 0％ (dry matter percentage,the control group),0.5％ (group A),1.0％(group B),1.5％ (group C) and 2％ (group D),respectively,in each stage.Every stage has 25 days.And the rumen fluid contents was collected per 5 days to detect the pH,ammonia nitrogen (NH3-N),microbial protein (MCP) and volatile fatty acid (VFA).The result showed that the pH value presented a trend of decreasing first and then increasing,with the urea concentration rising.And the lowest pH was 6.36-±-0.17 (B group),significantly lower than the other groups (P＜0.05).Between the all treatment groups,there was much significant difference in pH value(P＜0.05),too.For total VFA,all treatment groups were significantly higher than control group(P＜0.05).And the B group had the highest total VFA level,with a significant difference(P＜0.05).Compared with the control group,A group and B group was significantly higher in all VFA items(P＜0.05).But between A group and B group,there was no significant difference (P＞0.05) in VFA items,except the total VFA.In NH3-N,each treatment group was significantly higher than control group.And the D group had the significantly highest level compared with the other treatment group.Meanwhile,the treatment groups were significantly higher than control group,except the D group,in microbial protein content.The B group had the highest microbial protein content compared with the other treatment groups.To sum up,the B group had the best effect of urea addition.So,it is suggested that the diet with 1％ urea should be the safe and effective non protein nitrogen dosage for Qinchuan cattle.