日粮精料水平和蛋氨酸铬添加对滩羊瘤胃发酵特性、细菌和脂肪酸组成的影响

Effects of dietary concentrate level and chromium-methionine supplementation on ruminal fermentation,and ruminal bacterial and fatty acid composition in Tan lambs

为了研究日粮精料水平和蛋氨酸铬(Cr-Met)添加对滩羊瘤胃发酵参数、脂肪酸组成和细菌丰度的影响,选取40只体重相近[(21.00±1.23)kg,5月龄]且健康状况良好的滩羊公羔,随机分为4组,每组10只。LC组饲喂精粗比为35∶65的全混合饲粮,日粮中不添加Cr-Met;HC组饲喂精粗比为55∶45的全混合饲粮,日粮中不添加Cr-Met;HCM和HCH组均饲喂精粗比为55∶45的全混合饲粮,Cr-Met的添加量分别为0.75和1.50 g·d^(-1)·只^(-1)。在试验第65天晨饲后3 h通过各组滩羊口腔取瘤胃液,用于分析瘤胃发酵和瘤胃液脂肪酸组成以及细菌DNA的提取。结果表明:1)HC组滩羊瘤胃pH、乙酸比例和乙酸/丙酸显著低于LC组(P<0.05),但微生物蛋白(MCP)产量、丙酸和戊酸比例却显著高于LC组(P<0.05);与HC组相比,HCM组的乙酸/丙酸显著升高(P<0.05)。2)HC组反式油酸溶纤维丁酸弧菌和黄色瘤胃球菌的DNA丰度显著低于LC组(P<0.05),但解脂厌氧弧杆菌的DNA丰度却显著高于LC组(P<0.05);高精料日粮中添加Cr-Met线性降低了硬脂酸溶纤维丁酸弧菌、反式油酸溶纤维丁酸弧菌、蛋白溶解梭菌和解脂厌氧弧杆菌的DNA丰度(P<0.05),但黄色瘤胃球菌的DNA丰度却线性升高(P<0.05)。3)与LC组相比,HC组滩羊瘤胃内t11 C18:1(TVA)、trans C18:1、c9t11 CLA、t10c12 CLA、C18:2n6和C18:3n3的浓度显著降低(P<0.05),而C18:0的浓度则显著升高(P<0.05);高精料日粮中添加Cr-Met线性提高了TVA和trans C18:1的浓度(P<0.05)。综上所述,饲喂精粗比为55∶45的日粮抑制了部分氢化细菌的生长,Cr-Met的添加对机体共轭亚油酸的生成有一定的促进作用。

This study evaluated the effects of dietary concentrate level and chromium methionine(Cr-Met)supplementation on ruminal fermentation and fatty acid composition,and ruminal bacteria abundance in Tan lambs.Forty male Tan lambs[(21.00±1.23)kg body weight,5 months of age]were randomly assigned to four treatment groups with 10 lambs in each treatment.The treatments were:a low-concentrate(LC)diet(concentrate∶forage,35∶65)without Cr-Met supplementation;a high-concentrate(HC)diet(concentrate∶forage,55∶45)without Cr-Met supplementation;groups fed the HC diet with 0.75 or 1.50 g·d^(-1)·lamb^(-1) Cr-Met(HCM and HCH,respectively).Ruminal fluid was collected on day 65 with an oral stomach tube about 3 h after the morning feed and samples used for fermentation analysis,fatty acid composition determination and bacterial DNA extraction.It was found that:1)Ruminal pH,acetate proportion and acetate∶propionate were greater(P<0.05)with the LC diet whereas microbial crude protein,propionate and valerate proportions were greater(P<0.05)with the HC diet.The acetate∶propionate was greater(P<0.05)in the HCM group than in the HC group.2)For the HC diet,the DNAabundances of Butyrivibrio fibrisolvens vaccenic acid subgroup(Butyrivibrio VA)and Ruminococcus flavefaciens were decreased(P<0.05),compared with the LC diet,whereas the DNA abundance of Anaerovibrio lipolytica was increased(P<0.05).For lambs fed the HC diet,DNA abundances of B.fibrisolvens stearic acid subgroup,Butyrivibrio VA,Butyrivibrio proteoclasticus,and A.lipolytica showed a linear decrease(P<0.05)with increasing Cr-Met supplementation level;However,the DNA abundance of R.flavefaciens showed a linear increase(P<0.05).3)Compared with the LC group,the concentrations of t11 C18:1,trans C18:1,c9t11 CLA,t10c12CLA,C18:2n6,and C18:3n3 were decreased by the HC diet without Cr-Met supplementation whereas the concentration of C18:0 was increased.There was a linear increase in t11 C18:1 and trans C18:1 with increasing CrMet supplementation level in lambs fed the HC diet.The results suggest that the HC diet inhibited the growth of ruminal bacteria involved in the ruminal biohydrogenation process,and the addition of Cr-Met had a potentially positive effect on conjugated linoleic acid(CLA)synthesis in body tissue.