Effects Of Nonprotein Nitrogen From Different Sources On Rumen Fermentation Characteristics And Methionine Metabolism

In this study,ammonium chloride,biuret and glutamine were used as non-protein nitrogen sources to explore the effects of non-protein nitrogen from different sources on fermentation parameters,microbial diversity and methionine metabolism in rumen.We used double-outflow continuous culture fermentation technology,and selected three Xiangdong black goats with rumen fistula as the rumen fluid donors.Three non-protein nitrogens were added to the substrates of corn soybean meal and straw with a ratio of 1: 1 respectively with3 × 3 Latin square experiment design,6 fermentors were randomly divided into 3 groups: 1)ammonium chloride group(A);2)biuret group(B);3)glutamine group(C).The whole test is divided into three stages,the test period of each stage lasted for 8 days,the first 5 days was the adaptation period,the goat of three groups were added with the same amount of 2m L unlabeled methionine,and the last 3 days are the trial period,and the three groups are both added 20% [1-13C]-L-Met and 20% [methyl-2H3]-L-Met labeled methionine replaced 40% unlabeled methionine.The results showed that the average p H value of group A was significantly higher than that of groups B and C(P <0.01).The concentration of ammonia nitrogen in group C was 10.33 mg / d L,which was significantly higher than that in groups A and B(P <0.01).The level of MCP in group B was significantly lower than that of the other two groups(P <0.05).The concerntration of VFA(including propionic acid,butyric acid,isovaleric acid)in each group showed significant difference,and among them,the level of propionic acid in group C was 36.03% and 30.38% higher than that in groups A and B,respectively(P <0.01);furthermore,the concerntration of butyrate in Group C was 24.61%higher than Group A(P <0.05),and isovaleric acid of Group C was 60.19% and 36.89%lower than group A and B,respectively(P <0.01).There was no significant difference in the concerntraton of TVFA among three groups(P> 0.05).The Acetate/ Propionate in Group C was significantly lower than that of the other two groups(P <0.01).There was no significant difference in microbial diversity among three groups(P> 0.05).At phylum level,the relative abundance of Cyanobacteria,Planctomycetes,Elusimicrobia and Armatimonadetes in Group B was reduced in relative with Group C(P <0.05).At the genus level,the relative abundance of SP3-e08,Prevotellaceae＿UCG-001 and Ruminococcus＿1 in group A was increased compared with group B(P <0.05),while the relative abundance of Rikenellaceae＿RC9＿gut＿group and Butyrivibrio＿2 in group B was increased in comparison with other two groups(P <0.05).Using metabolomics to analyze the differential metabolites of each group,the results demonstrated that there were 7 different metabolites in the different non-protein nitrogen treatment groups to which methionine was added.The differential metabolites showed down-regulated in group A and group B(including L-Histidine and Hypoxanthine);the up-regulated differential metabolites of group A compared with group C included 2-methyl-4-(methylthio)-6-{[3-(trifluoromethyl)phenyl]thio} pyrimidine-5-carbonitrile and Senecionine,and the down-regulated differential metabolites include N,N-Bis(2-hydroxyethyl)formamide and L-Histidine;the level of DL-Alanine was decreased wihle group B compared with group C.In summary,the study revealed that glutamine was conducive to the synthesis of microbial protein,and reduced the ratio of acetic acid to propionic acid,so that the fermentation pathway tend to propionic acid type fermentation;ammonium chloride could improve the abundance of fiber-degrading bacteria Ruminococcus＿1 and protein-degrading bacteria SP3-e08 and Prevotellaceae＿UCG-001;three non-protein nitrogens displayed seven significantly different metabolites,there were the most metabolites between the ammonium chloride treatment group and the glutamine treatment group,there are four significant differences in metabolism,indicating that there were significant differences in the molecular composition and concentration between the two kinds of non-protein nitrogens-ammonium chloride and glutamine.