添加不同水平烟酰胺对泌乳奶牛体外发酵的影响

采用体外发酵法,研究烟酰胺(NAM)添加水平对泌乳奶牛瘤胃体外发酵指标的影响,探讨NAM影响生产性能的机理.选取3头装有永久性瘤胃瘘管的泌乳荷尔斯坦奶牛作为体外培养的瘤胃液供体,采用单因素随机试验设计,共有5个处理,每种处理均设3个重复.其中,A组为对照组,仅以基础日粮为发酵底物,B、C、D和E组在基础日粮基础上分别添加3、6、9和12 mg/100 g NAM.结果表明,发酵4h内,pH值没有显著的变化(P＞0.05),发酵8h后,对照组和添加12 mg/100 g NAM组显著下降到正常水平下(P＜0.05).从原虫蛋白浓度来看,添加9和12 mg/100 g NAM组显著低于对照组,而添加3和6 mg/100 g NAM组数值上高于对照组,但是差异不显著(P＞0.05).综合分析得出结论:添加6 mg/100 g NAM,能够维持正常的pH值,促进瘤胃微生物生长,特别是瘤胃原虫的生长,这可能是生产中添加NAM能提高生产性能的原因.建议促进瘤胃体外发酵的烟酰胺的适宜添加剂量为6 mg/100 g.

EFFECT OF DIFFERENT NICOTINAMIDE SUPPLEMENT LEVELS ON FERMENTATION IN VITRO OF LACTATING DAIRY COWS

This experiment was conducted to study the effect of different nicotinamide(NAM) supplement levels on fermentation in vitro of lactating dairy cows,and tried to study its mechanism in affecting production performance.Three lactation Holstein cows fitted with permanent rumen cannula were used to provide rumen fluid in vitro,basal diet was used as fermentation substrate.It was designed as randomized experiment of single factor into five treatments with three replicates.The treat of control group(group A) was added the basal diet as fermentation substrate and the treats in other groups were added the basal diet supplemented with 3(group B),6(group C),9(group D) and 12 mg/100 g(group E) NAM,respectively.The results showed that,4 h later,pH was not changed significantly(P>0.05),after 8 h,the group of control and adding 12 mg/100 g NAM were significantly decreased in unnormal levels(P<0.05).Parasite protein concentration of the groups of adding 9 and 12 mg/100 g NAM were significantly lower than the control group,while the groups of adding 3 and 6 mg/100 g NAM group were numerically higher than the control group,but the difference was not significant(P>0.05).These results indicated that adding 6 mg/100 g NAM can maintain normal pH for rumen microbial growth,especially for the growth of rumen protozoa,and that may explain why adding NAM can increase the production performance,and the suggested optimal level for rumen fermentation in vitro was 6 mg/100 g.