Effects Of Niacin On Microorganism System In The Rumen Of Cattle Under High-Concentrate Diet

To understand the effects of niacin on the ruminal fermentation, cellulose and diastase activity, and microbial ecology of cattle under high concentrate condition, the vivo experiments was used. The study used a self-contral-design, and three different diets fed to three Jinjiang cattles(400±20 kg BW) during three periods: the high-forage diet(forage to concentrate ratio was 80:20, HF) in period I, the high-concentrate diet(forage to concentrate ratio was 20:80, HC) in period II, and the high-concentrate diet supplemented with 800 mg/kg niacin(forage to concentrate ratio was 20:80, HCN) in period III. Rumen fluid was used to determin rumen fermentation indices, and microorganism anlaysis was the use Illumina MiSeq sequencing technology. The results showed that:(1) Compared with LC group, HC group caused a lewer level of ruminal pH value, significanty increased the production of NH3-N and butyric acid(P<0.05). In contrast with HC group, niacin addition gave higher level of ruminal pH value, significanty increased the production of propionic acid(P<0.05), decreased A/P(P<0.05), and tend to decreased the production of butyric acid(P>0.05).(2) Compared with LC group, HC group gave higher activities of carboxymethy cellulose, cellobiase, xylanasc and diastase(P<0.05). In contrast with HC group, niacin addition tend to decreased the carboxymethy cellulose and cellobiase activity(P>0.05), and increased the activities of diastase(P>0.05).(3) Compared with LC group,HC group caused a higher production of protozal protein and MCP(P<0.05), but the Ace,Chao and Shannon index were lower than those of HF group. In contrast with HC group,niacin addition further increased the production of protozal protein and MCP(P<0.05), but further decreased the Ace, Chao and Shannon index. Compared with LC group, HC group increased the abundance of Bacteroidetes(P<0.01), Ruminococcaceae, and Pseudobutyrivibrio(P<0.05), decreased the abundance of Lentisphaerae,Fibrobacteraceae, Fibrobacter and Ruminobacter(P<0.05). In contrast with HC group,niacin addition tend to increased the abundance of Actinobacteria(P<0.1), decreasede the abundance of Firmicutes, Spirochaetae, Butyrivibrio, Pseudobutyrivibrio, Treponema and Anaerovorax(P<0.1)。In the experiments, the high-concentrate diet may increase the abundant of butyrate producing bacterium and produce amounts of butyric acid, which is associated with a rapid decline in ruminal pH. The high-concentrate diet supplemented niacin may increase the abundant of protozal, and avoid the rapid fermentation of starch. Niacin addition decrease the abundant of butyrate producing bacterium and reduce the production of butyric acid,thereby stabilising the ruminal pH value.