Effect Of Feeding Methods On Fat Deposition Of Sunite Sheep

The content of fat metabolismenzymes,the expression of fat metabolism genes,the contents of fatty acid and the volatile flavor components of intramuscular fat(femoral biceps)and extramuscular fat(subcutaneous fat and tail fat)in 12-month-old Sunit Sheep under different feeding conditions(grzaed and concentrated)were measured by ELISA kit,Real time polymerase chain reaction(RT-PCR)and gas chromatography-mass spectrometry(GC-MS).The effects of grazing and feeding on the fat deposition of Sunit mutton were studied,and the mechanism of action was studied to explore measures to regulate intramuscular fat deposition.The results showed that the content of IMF in the grazing group was significantly higher than that in the concentrated group(p<0.05).The contents of a-linolenic acid,docosahexenoic acid(EPA)and docosahexenoic acid(DHA)and conjugated linoleic acid(CLA)in the grazing group were significantly higher than those in the concentrated group(p<0.05),the content of n-6 PUFA and n-6/n-3 ratio in the grazing group were significantly lower than those in the concentrated group(p<0.05),the contents of a-linolenic acid,EPA and DHA in intramuscular fat were significantly higher than those in extramuscular fat(p<0.05).The content of 2.3-octanedione in the grazing group was significantly higher than that in the concentrated group(p<0.05),the content of hexanal,nonanal and 1-octen-3-ol in the concentrated group was significantly higher than that in the grazing group(p<0.05),the total amount and type of flavor substances in intramuscular fat were significantly higher than those in extramuscular fat.In intramuscular fat,lipoprotein lipase(LPL)and carnitine palmitoyltransferase 1(CPT1)enzymes content and genes expression in the grazing group were significantly higher than that in the concentrated group(p<0.05),in extramuscular fat,acetyl-coa carboxylase(ACC),LPL,CPT1 and percoxisome proliferratoractivated receptor y(PPARy)enzymes content and genes expression in the concentrated group were significantly higher than those in the grazing group(p<0.05).The enzyme contents of ACC,LPL,CPT1 and PPARy in the three parts were in the order of biceps femoris>subcutaneous fat>tail fat,compared with the biceps femoris and subcutaneous fat,the expression of lipid metabolism genes in the tail fat were higher.Correlation analysis showed that the total amount of aldehydes was significantly positively correlated with linoleic acid,arachidonic acid,PUFA,n-3PUFA and a-linolenic acid(p<0.05).Octanal was significantly positively correlated with arachidonic acid and PUFA in intramuscular fat(p<0.05).High expressions of ACC,LPL,CPT1 and PPARy gene were beneficial to the deposition of IMF.High expression of CPT1 gene facilitates the deposition of polyunsaturated fatty acids(PUFA)in IMF(p<0.05),while high expression of PPARy gene inhibits the deposition of saturated fatty acids(SFA)in IMF(p<0.05).The high expression of the ACC gene facilitates the deposition of SFA in extramuscular fat,but inhibits the deposition of PUFA in extramuscular fat.Therefore,compared with feeding,grazing is more conducive to increase the LPL and CPT1 enzyme content and gene expression in intramuscular fat,thereby increasing the deposition of intramuscular fat content and unsaturated fatty acid content.