蛋氨酸羟基异丙酯对母犊牛瘤胃发酵和微生物区系的影响

目的]蛋氨酸羟基异丙酯(HMBi)作为饲料添加剂广泛用于补充反刍动物日粮中缺乏的蛋氨酸(Met),尽管HMBi拥有过瘤胃特性,但仍有部分在瘤胃中降解.研究拟探究HMBi对犊牛瘤胃发酵和微生物区系的影响.方法]选取36头体重在(101±10)kg的84日龄断奶后荷斯坦母犊牛并随机分为两个处理组,分别为对照组(PC,0...

Effects of 2-Hydroxy-4-(Methylthio)-Butanoic Acid on Rumen Fermentation and Microbiota in Holstein Female Calves

【Objective】2-Hydroxy-4-(Methylthio)-Butanoic Acid (HMBi) is widely used to satisfy the absent of methionine (Met) in ruminal diet. Although the characteristic of HMBi is a rumen protected product, there is still an amount of HMBi degraded in rumen, which should be taken seriously. Hence, this study was conducted to evaluate the effects of HMBi on rumen fermentation and microbiota. 【Method】The experiment was conducted for 97 days with 36 Holstein female calves aged about 84 day-old with (101±10) kg body weight, and those calves were allocated to 2 groups, including PC group (0.40% Met) and PCMet group (0.28% Met). The treatment was achieved by deducting HMBi in diet of PCMet group and made Met level 30% lower than that of PC group. The first 7 d were an adaptation to the diets and the next 90 d for sampling. The body weight was measured at 0 d and 90 d, respectivley. The dry matter intake was recorded daily throughout the whole trial period. The serum and rumen fluid samples from five calves in each group were sampled on day 90 to determine rumen fermentation parameters and microbial communities. 【Result】(1) Compared with PC group, the growth performance of PCMet group was not changed (P>0.05). The Met in serum of PCMet group had trend to be significantly decreased when compared with PC group (0.05<P<0.1); (2) The molar proportion of acetate and microprotein concentration in PCMet group was significantly decreased by Met deduction (P<0.05). There were no significant differences on concentrations of total volatile fatty acid and ammonia nitrogen between two groups (P>0.05). (3) The Shannon index of microbiota in PCMet group was lower than that in PC group (P<0.05). The PCoA and PREANOVA analysis showed the significant distinction between microbiota in two groups (P<0.05). Furthermore, the relative abundance of Firmicutes in PCMet group was decreased and the relative abundance of Bacteroidetes was increased when compared with PC group (P<0.05). At genus level, the relative abundance of Olsenella, Ruminococcus] gauvreauii group, Acetitomaculum, Eubacterium] nodatum group, and Coprococcus 1 were decreased in PCMet group (P<0.05). The correlation analysis showed that Eubacterium] nodatum group and Acetitomaculum were significantly correlated with acetate and Ruminococcus] gauvreauii group was significantly correlated with MCP (P<0.05, r>0.7). 【Conclusion】 The ruminal microbiota was inhibited by HMBi deduction, which led to the decrease of MCP and Shannon index. Among them, the acetogen was sensitive with HMBi. In conclusion, although HMBi was a rumen protected product, the part of HMBi degraded in rumen still had the ability to regulate rumen fermentation.