Effects Of Forage Types On Growth Performance,Meat Quality And Gastrointestinal Microbiota In Tan Sheep

In recent years,the meat products demand has undergone great changes.Quality and health are important indicators of consumers’concern.The production systems should be adjusted to meet consumers’demands.Ruminants can convert non-starch polysaccharides from plant sources which can not be digested by human beings into high-quality meat,eggs and milk for human consumption,and the rumen microorganism has an irreplaceable role in decompose plant cellulose or hemicellulose.Therefore,it is of great importance to develop potential sources of functional roughage for sustainable and healthy ruminant breeding.In this study,the grading index（GI）of 8 kinds of roughages commonly used in Northwest China was measured.Then,the feeding effect of Caragana koragana was compared with that of corn straw and alfalfa.The mixed feed pellets of 3 kinds of roughages were prepared into the mixed feed pellets for the breeding experiment of Tan sheep.The effects of forage types on growth,meat quality and gastrointestinal microflora of Tan sheep were studied by adding 40%Caragana korshinskii,corn straw and alfalfa respectively,and the feasibility and safety of Caragana korshinskii as a source of roughage for Tan sheep were systematically evaluated.The main results are as follows:1.The order of 8 forages GI values are as follows:Alfalfa（2.77）>Astragalus adsurgens（1.58）>Potato seedling（1.22）>Leymus chinensis（1.15）>Caragana（0.98）>Sorghum sudanense（0.47）>Wheatstraw（0.42）>Cornstalk（0.31）.2.There were not significant differences in daily gain,feed intake,feed to meat ratio and slaughter performance among ALF,CAR and COR in feeding experiment（P>0.05）.There were not significant differences in serum biochemical indexes（P>0.05）.Compared with CAR and COR groups,the apparent digestibility of neutral detergent fiber（NDF）in ALF group was significantly increased（P<0.05）,and the apparent digestibility of crude protein（CP）in ALF group and CAR group was significantly higher than COR group（P<0.05）.The contents of alanine,valine,phenylalanine,lysine and arginine in ALF group were significantly higher than CAR group（P<0.05）,the content of saturated fatty acids in ALF group and CAR group was significantly higher than COR group（P<0.05）.3.Further analysis of rumen tissue morphology,short chain fatty acid profile and microbial composition of rumen contents.We found thatumen papilla height in ALF group was significantly higher than other two groups（P<0.05）.There were not significant differences in p H and NH₃-N concentration of rumen contents among the three groups（P>0.05）,the content of total short chain fatty acids in ALF group was significantly higher thanin CAR group and COR group（P<0.05）,and the relative ratio of isobutyric acid and iso-valeric acid in CAR group was significantly lower than in COR group（P<0.05）.The Chao index of rumen microbial in ALF group was significantly lower than CAR group,and Shannon index in ALF group was significantly lower than that in COR group（P<0.05）.Compared with ALF group,the relative abundance of Christensenellaceae＿R-7,Preprevellaceae＿UCG-001,Mogibacterium,Marvinbryantia,Ruminococcaceae＿NK4A214,Lachnospiraceae＿UCG-002 and Desulfuromonas in CAR group were significantly increased（P<0.05）.The relative abundance of Ruminococcus＿2 was significantly decreased（P<0.05）.PICRUSt function prediction showed that the metabolism of starch and sucrose,fructose and mannitose,and fatty acid biosynthesis pathway in CAR group was significantly increased compared with ALF group（P<0.05）.and the abundance of carbon sequestration pathway,nitrogen metabolism,cysteine and methionine metabolism,lysine biosynthesis and histidine metabolism pathways in prokaryotes were significantly decreased（P<0.05）.4.Analysis the effect of roughage type for sheep intestinal tissue and microbiota.We found that,the relative abundance of unclassified＿f＿Peptostreptococcaceae,Ruminococcus＿2 is significantly higher in CAR group than ALF group in the ileum（P<0.05）.Function prediction found that the relative abundance of glycine,serine and threonine metabolism and lysine biosynthesis pathway in CAR group significantly increased compared with ALF group（P<0.05）.Forage type was not significant effect on cecal short chain fatty acid profile（P<0.05）.Compared with ALF group,Shannon index and Chao index in CAR group were significantly increased（P<0.05）;At the genus level,the relative abundance of Rikenellaceae＿RC and Phascolarctobacterium in CAR group were significantly increased compared with ALF group（P<0.05）.Function prediction using PICRUSt found that compared with ALF group,the abundance of pyruvate metabolism,butyric acid,lipid metabolism,C5-branched chain dibasic acid degradation metabolism,valine,leucine and isoleucine,phenylalanine metabolism,valine,leucine and isoleucine,lysine biosynthesis,histidine biosynthesis metabolism,glycine,serine and threonine metabolism,cysteine and methionine metabolism pathways increased significantly in CAR and COR group（P<0.05）.In conclusion,this study systematically evaluated the safety and feasibility of caragana as a new roughage.We proved that the application of CAR in Tan-sheep is safe and feasible,caragana feed does not significantly affect the growth of sheep phenotype and gastrointestinal tissue morphological development,its nutritional components of special chemicals can significantly improve the intestinal microbial components,promoting the absorb the intestinal carbohydrates and amino acids.This study provided scientific theoretical data for the development of caragana as ruminant rouge,promoted the wide application of caragana in ruminant feed,and provided a solution to alleviate the shortage of rouge sources for ruminant breeding.