Effects Of Feeding Regimens On Gastrointestinal Microbiota,Fatty Acid Metabolism And Meat Quality Of Sunit Sheep And Its Underlying Mechanism

This study was conducted to investigate the effects of different feeding regimens（Pastured（P group）,Pastured plus Captivity（PC group）and Captivity（C group）,12 in each group）on slaughter performance,carcass characteristics,meat quality,fatty acid metabolism and gastrointestinal microbiota of Sunit sheep by high throughput sequencing technology,real time polymerase chain reaction（RT-PCR）and gas chromatography-mass spectrometry（GC-MS）and bulid relationship.Finally,linseed-feeding was used to verify the relationship between fat deposition and gastrointestinal flora to provide scientific base for supporting sheep feeding practice in Inner Mongolia.A study was conducted to investigate the effects of different feeding regimens on slaughter performance,carcass characteristics and meat quality.The result showed that the slaughter rate of Sunite sheep in P group was significantly lower than that of the PC group and C group（P<0.05）.The bone weight was significantly higher and the net meat weight in PC group was significantly lower than that in P group and C group（P<0.05）.There was no significant difference in carcass weight,eye muscle area and back fat thickness among the three feeding regimens（P>0.05）.Feeding regimens had no significant difference in pH0 of longissimus dorsi muscle（P>0.05）,but had significant effect on pH24（P<0.05）.The lightness and shear stress of longissimus dorsi muscle in C group were higher than those in the P and PC group（P<0.05）,while the redness and yellowness of biceps femoris muscle were lower than those in PC group（P<0.05）.The crude protein content of longissimus dorsi muscle in PC group was significantly higher than that of P group（P<0.05）,but there was no significant difference in water content,fat content and ash content（P>0.05）.The fat content and water content of biceps femoris muscle in C group were significantly higher than that of P group and PC group（P<0.05）.A study was conducted to investigate the effects of different feeding regimens on fatty acid profile and the expression of fatty acid metabolism gene of muscle and adipose tissue in Sunit sheep.The results showed that The content of polyunsaturated fatty acids（PUFA）in muscle tissue and tail fat of P group and PC group was significantly lower than that of C group（P<0.05）,but there was no significant difference in saturated fatty acids（SFA）（P>0.05）.In adipose tissue,the content of monounsaturated fatty acids（MUFA）in PC group was significantly higher than that of P group（P<0.05）.The content of stearic acid in muscle tissue and subcutaneous fat in P group was significantly higher than that in C group（P<0.05）,and there was no significant difference in palmitic acid content（P>0.05）.In tail fat,the content of stearic acid was higher and the content of palmitic acid was lower in P group than that in C group（P<0.05）.The content of oleic acid of longissimus dorsi muscle and subcutaneous fat in PC group was significantly higher than that in P group and C group（P<0.05）,while the content of linoleic acid in C group was significantly higher than that in P group and PC group（P<0.05）.The contents of linolenic acid（ALA）and conjugated linoleic acid（CLA）in muscle tissue and tail fat were significantly higher than those in C group（P<0.05）.The contents of ALA,EPA and DHA in muscle tissue were significantly higher than those in adipose tissue（P<0.05）.In P group,the mRNA expression of SCD and ACC gene in subcutaneous fat and CPT1 gene mRNA expression in longissimus dor si muscle and tail fat was higher than that of C group（P<0.05）.The mRNA expression of LPL,FDAS1 and FADS2 genes in muscle and adipose tissue of P group was higher than that of C group（P<0.05）,and the mRNA expression of FAPB4 and PPARy genes in muscle tissue of grazing group was higher than that of C group and PC group（P<0.05）.The mRNA expression of CPT1,FADS1 and FADS2 genes in muscle tissue was higher than that in adipose tissue（P<0.05）,while the expression of ACC,FAS,SCD,FABP4 and PPAR gamma genes was lower than that in adipose tissue（P<0.05）.A study was conducted to investigate the effects of different feeding regimens on the diversity and relative abundance of gastrointestinal microbiota and SCFA in Sunit sheep.The results showed that the alpha diversity of gut and rumen microbiota of Sunit sheep in P group was significantly higher than that in BF group（P<0.05）.Gut and rumen microbiota of Sunit sheep were mainly Bacteroidetes and Firmicutes.The relative abundance of Firmicutes in rumen microbiota of grazing group was higher than that of C group（P<0.05）,while the relative abundance of Proteobacteria in P and PC group was lower than that in BF group（P<0.05）.The relative abundance of Prevotella,RC9_gut_groupy Bacteroides,Butyrivibrio and Quinella in the rumen of grazing group was higher than that of the C group,while the number of Butyrivibrio in the C group was the highest.The relative abundance of Firmicutes and Bacteroidetes in the gut of P group was higher than that in C group（P<0.05）,while the relative abundance of Proteobacteria was lower than that in C group（P<0.05）.The relative abundance of Bacteroides,RC9_gut_group and Alistipes in the intestine of P and PC group were higher than that of C group（P<0.05）.The number of Prevotella was higher in C group and the number of Ruminococcus and Phascolarctobacterium was higher in the PC group.The contents of acetic acid and valeric acid in rumen of P group were significantly higher than those in PC group（P<0.05）,and butyric acid was significantly higher than that of C group（P<0.05）.Correlation analysis showed that RC9_gut_group and Butyrivibrio in rumen could promote the deposition of n-3 PUFA in muscle.The mechanism of the effect of nutrition level on fat metabolism and gastrointestinal flora of Sunit sheep showed that linseed-feed increased the growth rate,the content of ash and water（P<0.05）and decreased the slaughter rate,PH24,shear stress and fat content（P<0.05）.The relative abundances of RC9_gut_group,Treponema₂,Bifidobacterium and Fibrobacter in flaxseed group were significantly higher than those in control group（P<0.05）,while the relative abundances of Ruminococcus and Selenomonas₁ were higher than those in control group（P<0.05）.The contents of stearic acid,ALA,EPA and DHA in the longissimus dorsi muscle of linseed group were higher than those in the control group（P<0.05）,while the contents of palmitic acid was lower than those in the control group（P<0.05）.In summary,it is further verified that increasing the abundance of RC9_gut_group in the rumen was beneficial to the deposition of n-3 PUFA in the muscle by feeding on a linolenic acid-rich diet.