Effects Of House-feeding At Low-altitude On Yak Meat Performance And Genes Expression Related To Meat Quality

House-feeding yak at low-altitude is an important method to alleviate the conflict between grass and livestock in Tibetan areas,and it can also effectively solve the problem of slow growth and development of yak in the cold season,promoting the accumulation of intramuscular fat and improving the quality of muscle of yak.Ten healthy male yaks of similar body weight and physical condition at the age of 36 months were randomly divided into house-feeding group(GH,Agricultural Districts in Guanghan,altitude:600 m,whole house-feeding)and grazing group(HY,Yak Breeding Technology Park in Hongyuan,altitude:3,500 m,naturally grazed in the traditional model).The trial period is 150days.The purpose of our study was to investigate the effects of house-feeding at low-altitude areas on yak muscle quality,growth and development,slaughter performance,and serum parameters.And to screen and identify differentially expressed genes and lncRNAs in longissimus dorsi muscle tissue of yak under different feeding condition,and to annote their function;screening the crucial mRNA and lncRNA was related to fat synthesis and metabolism;and the lncRNA-mRNA regulatory network was constructed.The main findings are as follows:1.The weight gain effect and slaughter performance indicators which is including the weight of the yak,pure meat weight,slaughter rate and pure meat rate of house-feeding yaks were extremely significantly higher than those of the grazing group(P<0.01).The dietary quality of the longissimus dorsi muscle in house-feeding group was significantly improved:the brightness(L~*),cooked meat rate and intramuscular fat(IMF)content were significantly higher than those in the grazing group(P<0.05),while the shear force was significantly lower than the grazing group(P<0.05).The contents of ether extract(EE),palmitic acid(C16:0)and stearic acid(C18:0)were extremely significantly higher than those in the grazing group(P<0.01).The contents of flavor amino acid(FAA),saturated fatty acids(SFA),polyunsaturated fatty acids(PUFA)and trans fatty acids(TFA)were significantly higher than those in the grazing group(P<0.05).2.The blood glucose(GLU)and the enzyme activity of fatty acid synthase(FAS)in the house-feeding group were significantly higher than those in the grazing group(P<0.05).And the content of triglyceride(TG),total cholesterol(TC)and the enzyme activity of acetyl-Co A carboxylase(ACC)were extremely significantly higher than those in the grazing group(P<0.01).The content ofβ-Hydroxybutyric acid(BHBA)was extremely significantly lower than the grazing group(P<0.01),he enzyme activity of hormone-sensitive lipase(HSL)was significantly lower than the grazing group(P<0.05).3.6 libraries obtained 112.79～133.39 Mb Raw reads respectively;high-quality data(clean reads)were over 99%after filtering.The clean reads was located at the yak reference genome about 83%.The analysis of reads classification annotation and alternative splicing showed that only 0.2～0.4%genes were aligned to lncRNA,and reads were mainly splicing in the way of exon jumping.A total of 406annotated lncRNAs and 14,570 novel lncRNAs and 6,974 transcripts of uncertain coding potential(TUCP)were obtained after screening;and there are 34,665 mRNA transcripts,of which 8,973 are novel transcripts and 25,692 have been annotated mRNA.4.Significantly differentially expressed 233 mRNAs(133 up-regulated and 100 down-regulated)were obtained in the longissimus dorsi muscle of house-feeding and grazing yak.Analysis of GO enrichment analysis of differential mRNA found that Differential mRNA GO enrichment analysis found that biological processes related to muscle development and lipid metabolism are significantly enriched in pathways,including protein linkage,glycerolipids,triglycerides,and neutral lipids.Analysis of KEGG signaling pathway of differential mRNA showed that pathways related to muscle development and fat metabolism was significantly enriched to tight junctions,actin synthesis,glycerolipid metabolism,MAPK signaling pathway and glycerophospholipid metabolism.The differential genes MAPKAP1,ACTC1,MYH7,GPAM,MAP2K3,MAPKAP1,and AGK were significantly enriched in these pathways.5.Significantly differential expression of 69 lncRNAs(35 up-regulated and 34 down-regulated)and 105 TUCP(51 up-regulated and 54 down-regulated)were obtained in the longissimus dorsi muscle of house-feeding and grazing yak.The prediction analysis of lncRNA Cis-acting showed that 11,252lncRNAs targeted 11,469 target genes,and 4,602 TUCPs targeted 8,364 target genes in yak.Prediction analysis of lncRNA Trans-acting revealed that 12,187 lncRNAs targeted 15,083 target genes,and 5,011TUCPs targeted 11,470 target genes.GO and KEGG enrichment analysis of target genes of differentially expressed lncRNA,TUCP Cis-acting and Trans-acting found that lncRNA(XLOC＿107261,XLOC＿007308,XLOC＿049235,XLOC＿076785,XLOC＿018419,XLOC＿122806,XLOC＿071250,XLOC＿115783)and target genes(FGF1,GADD45A,MAPK8,MAPKAP1,LEP,LEPR,CAMKK2,STAT3)significantly enriched the MAPK pathway and adipokine pathway,it may be involved in biological processes such as muscle fiber development,fat digestion and absorption,and fat cell differentiation.6.By constructing a co-expression network of target genes of lncRNA trans-acting and differentially expressed lncRNA,27 crucial lncRNAs(such as XLOC＿059072,XLOC＿145823,XLOC＿122806,XLOC＿076785)related to intramuscular fat deposition and their corresponding 52target genes(such as LEP,PLIN2,ADIPOR1,ELOVL7,SCD,TRIB3)were screened,these differential genes and lncRNA are mainly involved in biological processes and pathways related to fat deposition.In summary,our study provides basic data for exploring the effect of house-feeding on muscle quality of yak,and enriches yak transcriptome and lncRNA data information related to regulate or control muscle development and intramuscular fat deposition,and it provides a theoretical basis for further research on yak muscle development and intramuscular fat deposition,and so on.