不同精粗比饲粮中添加酵母培养物对牦牛瘤胃体外发酵参数的影响

Effects of Yeast Culture Supplementation in Diet with Different Concentrate to Forage Ratios on in Vitro Rumen Fermentation Parameters of Yaks

本试验旨在探讨不同精粗比饲粮中添加酵母培养物(YC)对牦牛瘤胃体外发酵参数的影响。采用3×6两因素交叉分组试验设计,在3个精粗比(40∶60、50∶50、60∶40)饲粮中分别添加6个水平(0、0.5%、1.0%、1.5%、2.0%和2.5%)的YC,制备出18底物进行体外发酵。结果表明:1)饲粮精粗比对产气量、干物质降解率(DMD)、粗蛋白质降解率(CPD)、酸性洗涤纤维降解率(ADFD)、中性洗涤纤维降解率(NDFD)有显著影响(P<0.05),50∶50组和60∶40组DMD、CPD、NDFD、ADFD显著高于40∶60组(P<0.05)。饲粮YC添加水平对产气量、CPD、NDFD和ADFD有显著影响(P<0.05),0.5%组产气量和CPD显著高于其他各组(P<0.05)。饲粮精粗比和YC添加水平对CPD有显著的互作效应(P<0.05)。2)饲粮精粗比对pH及氨态氮(NH3-N)、微生物蛋白(MCP)含量有显著影响(P<0.05)。40∶60组pH显著高于50∶50组和60∶40组(P<0.05),60∶40组NH3-N含量显著低于40∶60组和50∶50组(P<0.05),40∶60组M CP含量显著低于50∶50组和60∶40组(P<0.05)。饲粮YC添加水平对NH3-N和M CP含量有显著影响(P<0.05),0.5%组NH3-N和M CP含量显著高于其他各组(P<0.05)。3)饲粮精粗比和YC添加水平对总挥发性脂肪酸(TVFA)含量和乙酸、丙酸、异丁酸、丁酸、异戊酸、戊酸比例及乙酸/丙酸均有显著影响和互作效应(P<0.05)。60∶40组TVFA含量和丁酸比例显著高于40∶60组和50∶50组(P<0.05),40∶60组乙酸、异戊酸比例以及乙酸/丙酸显著高于60∶40组和50∶50组(P<0.05),50∶50组异丁酸和戊酸比例显著高于40∶60组和60∶40组(P<0.05)。1.0%组异丁酸、丁酸、异戊酸、戊酸比例显著高于其他各组(P<0.05),乙酸/丙酸显著低于其他各组(P<0.05)。综上所述,在本试验条件下,饲粮精粗比和YC添加水平对牦牛体外瘤胃发酵产气量、养分降解率和发酵参数有一定影响。饲粮精粗比以50∶50和60∶40为宜,YC添加水平以0.5%和1.0%为宜。

This experiment was conducted to investigate the effects of yeast culture(YC)supplementation in diet with different concentrate to forage ratios on in vitro rumen fermentation parameters of yaks.Five levels(0,0.5%,1.0%,1.5%,2.0%and 2.5%)of YC were supplemented in diet with three concentrate to forage ratios(40∶60,50∶50 and 60∶40)to formulate 18 kinds of subtracts using 3×6 two factors cross group experiment design.The result showed as follows:1)dietary concentrate to forage ratio had significant effects on gas production,dry matter degradation rate(DMD),crude protein degradation rate(CPD),acid detergent fiber degradation rate(ADFD)and neutral detergent fiber degradation rate(NDFD)(P<0.05),and the DMD,CPD,NDFD and ADFD of 50∶50 group and 60∶40 group were significantly higher than those of 40∶60 group(P<0.05).Dietary YC supplemental level had significant effects on gas production,CPD,NDFD and ADFD(P<0.05),and the gas production and CPD of 0.5%group were significantly higher than those of other groups(P<0.05).Dietary concentrate to forage ratio and YC supplemental level had significant interaction on CPD(P<0.05).2)Dietary concentrate to forage ratio had significant effects on pH and ammonia nitrogen(NH3-N)and microbial protein(MCP)contents(P<0.05).The pH of 40∶60 group was significantly higher than that of 50∶50 group and 60∶40 group(P<0.05),the NH3-N content of 60∶40 group was significantly lower than that of 40∶60 group and 50∶50 group(P<0.05),and the MCP content of 40∶60 group was significantly lower than that of 60∶40 group and 50∶50 group(P<0.05).Dietary YC supplemental level had significant effects on NH3-N and MCP contents(P<0.05),and the NH3-N and MCP contents of 0.5%group were significantly higher than those of other groups(P<0.05).3)Dietary concentrate to forage ratio and YC supplemental level had significant effects and significant interaction on total volatile fatty acid(TVFA)content and percentages of acetate,propionate,isobutyrate,butyrate,isovalerate and valerate and acetate/propionate(P<0.05).The TVFA content and butyrate percentage of 60∶40 group were significantly higher than those of40∶60 group and 50∶50 group(P<0.05),the acetate and isovalerate percentages and acetate/propionate of40∶60 group were significantly higher than those of 60∶40 group and 50∶50 group(P<0.05),and the butyrate and valerate percentages of 50∶50 group were significantly higher than those of 40∶60 group and 60∶40 group(P<0.05).The isobutyrate,butyrate,isovalerate and valerate percentages of 1.0%group were significantly higher than those of other groups(P<0.05),and the acetate/propionate was significantly lower than that of other groups(P<0.05).In conclusion,under the conditions of this experiment,dietary concentrate to forage ratio and YC supplemental level have effects on gas production,nutrient degradation rates and fermentation parameters in vitro fermentation.The optimal concentrate to forage ratios are 50∶50 and 60∶40,and the optimal YC levels are 0.5%and 1.0%.