日粮精粗比对活体外瘤胃发酵和烟酸、烟酰胺合成的影响

本试验旨在研究日粮精粗比对活体外瘤胃发酵和烟酸、烟酰胺合成的影响。以4头装有永久性瘤胃瘘管的成年荷斯坦阉公牛作为瘤胃液供体,选用淀粉、微晶纤维素、酪蛋白3种成分配制成相同粗蛋白质水平(13.5%,DM)和不同精粗比(30:70、50:50、70:30,DM)的3种纯合日粮作为发酵底物。应用人工瘤胃体外产气量法进行培养发酵并测定产气量、挥发酸及发酵液中烟酸、烟酰胺含量的变化。结果表明,提高日粮精粗比可极显著降低发酵液pH、乙酸/丙酸摩尔比、乙酸摩尔比(L,P<0.01),显著降低氨态氮浓度(L,P<0.05),但却极显著增加72 h产气量、总挥发酸浓度、丙酸和丁酸摩尔比(L,P<0.01)。随日粮精粗比的提高,瘤胃发酵液中总烟酸(烟酸+烟酰胺)、烟酰胺浓度在24和48 h均呈线性增加(L,0.050.10)。由此得出,日粮精粗比可改变活体外瘤胃发酵模式和影响瘤胃微生物合成总烟酸和烟酰胺,且随日粮精粗比的上升,瘤胃合成总烟酸、烟酰胺的数量呈线性增加趋势。

Effect of Dietary Concentrate to Forage Ratio on Rumen Fermentation and Microbial Synthesis of Niacin,Niacinamide in vitro

The gas production procedure was conducted to determine the effect of different concentrate to forage ratio on rumen fermentation parameter and rumen microbial synthesis of niacin,niacinamide (NAM),and nicotinic acid (NA) in vitro.Rumen fluid was collected from four Holstein adult steer with permanent rumen fistula,and three dietary substrates with different concentrate to forage ratios (30:70,50:50,70:30,DM) at an equal crude protein level of 13.5% were formulated by adjusting inclusion levels of starch,avicel and casein.The results showed that with the concentrate to forage ratios increased,the in vitro rumen pH,molar percentages of acetic and acetate to propionate were extremely significantly decreased (L,P<0.01),the ammonia-N concentration was significanthy decreased (L,P<0.05),whereas the 72 h gas production,molar percentages of propionate,butyrate and total VFA were extremely significantly increased (L,P<0.01).With the dietary concentrate to forage ratios increased,the concentrations of total niacin (nicotinic acid+niacinamide),niacinamide were increased at 24 and 48 h (L,0.050.10).In conclusion,dietary concentrate to forage ratio had a greater effect on rumen fermentation parameters and synthesis of niacin,niacinamide,and as dietary concentrate to forage ratios increased,the concentrations of total niacin and niacinamide had an increasing tendency.