Effects Of Lactic Acid Bacteria On Gastrointestinal Microbiota,Protein Metabolism And Meat Quality Of Sunit Sheep

In this study,a total of 24 Sunit sheep aged 3 months old were randomly divided into four groups,control group（C）,1%lactic acid bacteria group（L1）,2%lactic acid bacteria group（L2）and 3%lactic acid bacteria group（L3）.The control group was fed the basal diet and the experimental group was supplemented with 1%,2%and 3%of lactic acid bacteria according to the quality of the basal diet.Samples were taken after 90 days of feeding to investigated the effects of dietary supplementation with lactic acid bacteria on slaughter performance,carcass quality,meat quality,gastrointestinal flora and protein metabolism in Sunit sheep using High-throughput sequencing and Real-time fluorescence quantitative PCR,which will lay a theoretical foundation for the improvement of protein metabolism and meat quality by regulate the gastrointestinal flora of sheep.The slaughter performance,carcass quality and meat quality of Sunit sheep were studied.The slaughter rate and eye muscle area of L1 group and bone-meat ratio of L3group were significantly higher than those in the C group（P<0.05）,the cooking loss and ash content of two muscle parts（LD muscle and BF muscle）of Sunit sheep in the L1group,L2 group and L3 group were significantly reduced（P<0.05）.Compared to group C,the p H_24hvalue and intramuscular fat content of the LD muscle of Sunit sheep in the L1group were significantly increased（P<0.05）,the shear force value of the BF muscle was significantly decreased and increased,respectively（P<0.05）;the p H_24hvalue of the LD muscle in L2 group and L3 group were significantly increased（P<0.05）.Analysis of the diversity and flora composition of the gastrointestinal tract of Sunit sheep revealed.Theα-diversity of the gastrointestinal flora of Sunit sheep was significantly increased by the addition of lactic acid bacteria,the Ace and Chao1 indices of rumen microorganisms in L3 group were significantly higher than those in C group（P<0.05）,and the Ace and Chao1 indices of intestinal microorganisms in L1 group and L2group were significantly higher than those in C group（P<0.05）.The rumen flora and intestinal flora of Sunit sheep were mainly dominated by the Bacteroidetes and Firmicute.At rumen microbiome phylum level,compared with group C,significantly higher abundance values were observed for three groups of the Bacteroidetes and the Verrucomicrobia（P<0.05）,and the abundance values of the Firmicute were significantly lower in the L1 group（P<0.05）;at rumen microbiome genus level,compared with group C,significantly higher abundance values were observed for three groups of Prevotella＿1,Succiniclasticum,Christensenellaceae＿R-7＿group and Fibrobacterand（P<0.05）.At gut microbiome phylum level,compared with C group,L1 group and L2 group had significantly higher abundance values of Firmicute,Spirochaetes and Tenericutes（P<0.05）,significantly lower abundance values of Proteobacteria（P<0.05）.At gut microbiome genus level,compared with C group,significantly higher abundance values for three groups of Ruminococcaceae＿UCG＿013 and Prevotella＿1（P<0.05）,significantly lower abundance values of Succinivibrio were observed（P<0.05）.The protein metabolism in Sunit sheep was explored,and we found that,among the serum protein biochemical indicators,the ALB content,ALT and AKP activity were significantly higher in the L1 group than in the C group（P<0.05）,the TP content was significantly higher in L1 group and L2 group than in C group and L3 group（P<0.05）and the BUN content was significantly lower than C group（P<0.05）.Among the serum amino acids,the levels of TAA,TEAA and BCAA in serum were significantly higher in L1 group and L2 group than C group（P<0.05）.Among the muscle amino acids,the TAA and TEAA content of the two muscle parts in L1 group and the DAA content of the LB muscle were significantly higher than C group（P<0.05）.Compared with C group,L1 group had significantly higher of AKP activity in the two muscle parts of Sunit sheep（P<0.05）,and L2 group had significantly higher of LDH activity in the BF muscle（P<0.05）.In the protein anabolism pathway,the m RNA relative expression levels of Akt1,mTOR and eIF4E were significantly up-regulated in the LD muscle of the three groups（P<0.05）,and the m RNA relative expression levels of IGF-1,p70S6K1 and 4E-BP1 in L2 group and L3group（P<0.05）were significantly up-regulated;the m RNA relative expression levels of Akt1,p70S6K1 and eIF4E in the BF muscle of the three groups were significantly up-regulated（P<0.05）,and the m RNA relative expression levels of PI3K and mTOR were significantly up-regulated in L1 group（P<0.05）.In the protein catabolism pathway,the m RNA relative expression levels of Atrogin-1 in the LD muscle were significantly down-regulated in L1 group（P<0.05）,and Atrogin-1 and Mu RF1 in the BF muscle were also significantly down-regulated（P<0.05）,which influenced the protein anabolism and catabolism in Sunit sheep.