The Effect Of Heat Stress On The Growth Performance,meat Quality And Rumen Microorganism In Hu Sheep

The purpose of this experiment is to study the effect of heat stress（HS）on the production performance of Hu sheep and its mechanism.This experiment use twelve 12-month-old Hu sheep rams as experimental materials and constructs the HS model of Hu sheep through artificial temperature control to understand the effect of HS on the growth performance,slaughter performance and meat quality;Using the longissimus dorsi muscle samples as materials,the differentially expressed genes were screened by RNA-seq technology,and conducted the GO and KEGG pathways enrichment analysis to screen the candidate genes closely related to muscle development and meat quality;Using rumen fluid samples as materials,the differential rumen microbiota were screened by 16S r DNA amplicon high-throughput sequencing,and bioinformatics analysis and function prediction were carried out.The main test results are as follows:1.Compared with the control group（C group）,the relative expression of HSP60 gene in longissimus dorsi muscle of Hu sheep in heat stress group（HS group）was significantly increased（P<0.01）,the relative expression of HSP70and HSP110 gene was significantly increased（P<0.05）,and the concentration of HSP70 in serum was significantly increased（P<0.05）;The respiratory rate of Hu sheep in HS group increased significantly（P<0.01）.Heat stress significantly reduced the average daily gain（P<0.05）and the average daily food intake of Hu sheep（P<0.01）.The slaughter performance of heat stressed Hu sheep,such as net meat weight,bone weight,meat production rate and bone meat ratio,decreased significantly（P<0.05）.Heat stress significantly increased the yellowness b*,drip loss rate,p H_24h（P<0.05）,significantly reduced the p H_45min（P<0.05）of longissimus dorsi muscle of Hu sheep.In the longissimus dorsi muscle of heat stressed Hu sheep,the gene expression of My HCⅡa and My HCⅡx was significantly lower than that of the C group（P<0.01）,and the gene expression of My HCⅡb was significantly higher than that of the C group（P<0.05）.In muscle of heat stressed Hu sheep,the activities of MDH and SDH were significantly lower（P<0.05）and LDH was significantly higher than those in the C group（P<0.05）,indicating that HS reduced the growth performance,slaughter performance and meat quality of Hu sheep.2.The results of transcriptome sequencing showed that compared with the C group,180 differentially expressed genes（log₂|Fold Change|>1,P<0.05）were screened from the longissimus dorsi muscle of Hu sheep in the HS group,including 71 up-regulated and 109 down-regulated differentially expressed genes（P<0.05）.Through functional analysis of the differentially expressed genes,it was found that they were enriched in the signal pathways related to muscle development and fat metabolism,such as focal adhesion,calcium signaling pathway,ECM-receptor interaction and PPAR signaling pathway.3.The results of 16S r DNA sequencing of rumen fluid showed that compared with the C group,the dominant bacteria in the HS group were Firmicutes,Bacteroidetes and Tenericutes at the phylum level;The dominant bacteria are Quinella and Rikenellaceae＿RC9＿gut＿group,Succiniclasticum at the genus level.The analysis of rumen microbial diversity between the two groups showed that at the phylum level,the Firmicutes and Verrucomicrobia of Hu sheep in HS group were significantly higher than those in C group（P<0.05）,while Bacteroidetes were significantly lower than those in C group（P<0.05）.At the genus level,[Eubacterium]＿ventriosum＿group,[Anaerorhabdus]＿furcosa＿group,Coprococcus＿1,Lachnoclostridium＿1 of Hu sheep in HS group was significantly higher than those in C group（P<0.01）;Lachnospiraceae＿UCG-002,Lachnospiraceae＿UCG-006,Oribacterium were significantly higher than those in C group（P<0.01）;Rikenellaceae＿RC9＿gut＿group,uncultured＿bacterium＿f＿Bacteroidales＿RF16＿group,uncultured＿bacterium＿o＿Bacteroidales,uncultured＿bacterium＿o＿Izimaplasmatales was significantly lower than that in group C（P<0.05）.Functional prediction analysis found that at the first level,it mainly involves Metabolism,Environmental Information Processing and Cellular Processes.In the second level,it mainly involves Membrane Transport,Energy Metabolism,Biosynthesis of Other Secondary Metabolites and Cellular community–prokaryotes.In the second level,the relative abundance of AMPK Signaling Pathway,ABC Transporters and Phosphotransferase System（PTS）,Nitrogen Metabolism and Methane Metabolism in the HS group was significantly higher（P<0.05）.The relative abundance of Glycerophospholipid Metabolism,Glycine,Serine and Threonine Metabolism,Inositol Phosphate Metabolism of Hu sheep in the HS group was significantly decreased（P<0.05）.In conclusion,HS significantly reduced the growth performance,slaughter performance and meat quality of Hu sheep.HS affects the metabolism and absorption of nutrients by changing the gene expression level in muscle and rumen microbial diversity,and then affecting the weight gain,muscle growth and meat quality of Hu sheep.HS seriously affects the production performance of livestock and poultry,which needs to be paid attention to and solved in the breeding process.