The Effect Of Energy Restriction On Fat Deposition And Mechanism In Sheep

Sheep production systems in northwest China depend mostly on natural grasslands.Seasonal growth and maturity fluctuations can cause periodical restrictions in food quality and quantity.Consequently,the study objective was to compare fat deposition,mutton texture characteristics,fatty acid profiles,and Lipid metabolism genes expressions in lambs under ME restrictions similar to seasonal changes observed in the natural grasslands of northwest China.The results showed that:(1)Feeding lambs a restricted metabolizable energy ration to mimic grass metabolizable energy density and intake seasonal changes had a significant(P<0.05)influence on mutton nutrition and texture characteristics.Metabolizable energy restriction significantly increased moisture,reduced dry matter,crude protein,crude fat of mutton,ash and carbohydrate was not affected by metabolizable energy restriction.Furthermore,metabolizable energy restriction resulted in higher shear force,hardness,conglutination and chewiness.(2)Feeding lambs a restricted metabolizable energy ration to mimic grass metabolizable energy density and intake seasonal changes had a significant(P<0.05)influence on fat diposition.Restricting metabolizable energy resulted in lower IMF of longissimus dorsi and biceps brachii,but had no significant influence on IMF of biceps femoris.Compared to lambs fed the control group,fat deposition index,including gastrointestinal fat index,kidney fat,abdominal fat index,tail fat,subcutaneous fat,omental fat,visceral fat,and total fat except testicular and heart fat decreased significantly.(3)Metabolizable energy restriction was a significant influence on fat profiles(P<0.05).C18:0,CLA,MCSFA,OCSFA,SFA,n-3 PUFA increased significantly compared to lambs fed the control group,C18:1n9c,USFA,MUFA,and the rations of USFA/SFA?MUFA/SFA?PUFA/SFA(except biceps femoris)in IMF decreased significantly.The fatty acid composition of adipose tissue was significantly different from that of IMF,SFA adipose tissue increased significantly compared to lambs fed the control group,USFA and MUFA decreased significantly.except OCSFA,and n-6/ n-3 PUFA,there was no affect on the fatty acid of omental fat compared to lambs fed the control group.(4)The fatty acid composition was significantly different in different position(P<0.05).Compared to visceral and subcutaneous fat,IMF had lower significantly SFA?n-6/n-3 PUFA,higher USFA,MUFA,PUFA,n-3 PUFA,EFA,USFA/SFA,MUFA/SFA,PUFA/SFA.There was no difference in the content of fatty acid in tail fat and intramuscular fat except PUFA,EFA,n-6/n-3 PUFA,and PUFA/SFA.Compared to visceral fat,SFA decreased significantly,and USFA ? MUFA ?USFA/SFA?MUFA/SFA increased significantly in subcutaneous fat?(5)There was a significant correlation between IMF and fatty acid composition,and some fatty acid(P<0.05).IMF was significantly positively correlated with C18:2n6c,CLA,EPA,USFA,PUFA,n-6 PUFA,EFA,n-6/n-3,PUFA,MUFA/SFA,MUFA/SFA,PUFA/SFA,and was significantly negative correlated with C18:00,SFA,and n-3 PUFA?(6)Metabolizable energy restriction was a significant influence on FAS?PPAR??HSL?SCD expression(P<0.05).Restricting metabolizable energy resulted in lower FAS?PPAR??SCD expression,and higher HSL expression in longissimus dorsi,kidney fat,subcutaneous fat,omental fat,and tail fat.Furthmore,FAS?PPAR?genes sensitive in tail fat and subcutaneous fat when feeding metabolizable energy restriction,and HSL?SCD genes sensitive in visceral fat?(7)The mRNA expression of FAS,PPAR,HSL and SCD related fat metabolism genes all were depot-specificity(P<0.05).The expression level of FAS?PPAR??HSL in adipose tissue was significantly higher than that of muscle,and the expression of FAS?PPAR? in subcutaneous and kidney fat was significantly higher than that of other tissues,the expression of HSL?SCD in tail fat was significantly higher than that of other tissues.(8)There was a significant correlation between IMF and FAS?HSL?SCD expression(P<0.05).IMF was significantly positive correlation with FAS?SCD,and was significantly negative correlation with HSL.(9)The mRNA expression of FAS was significantly negative correlation with PUFA,n-3 PUFA.The mRNA expression of PPAR? was significantly positive correlation with SFA,and was significantly negative correlation with USFA?MUFA?PUFA ? n-3 PUFA.The mRNA expression of HSL was significantly positive correlation with MUFA,and was significantly negative correlation with PUFA?EFA.The mRNA expression of SCD was significantly negative correlation with SFA,and was significantly positive correlation with USFA.(10)The 6 principal components extracted from 38 fatty acids were used as synthetic variables to evaluate the status of IMF fatty acids by principal component analysis(PCA),The fatty acid C4:0,C6:0,C15:0,C16:0,C17:0,C18:0,C23:0,C24:0,C20:1,18:1n9c,and C20:4n6 as 38 the comprehensive evaluation index variable fatty acid.In summary,reatricting grass metabolizable energy,the fat in sheep was mobilized to oxidize and energy supply,and the nutrient composition and texture quality decreased,the contents of SFA and n-3 PUFA in fatty acids were increased,Sheep in natural grazing system should be fed reasonably in cold season.FAS,PPAR?,SCD decreased,on the contrary,HSL increased.Furthermore,FAS and PPAR were more sensitive in tail fat and subcutaneous fat.This suggests that fat deposition begins with the tail and subcutaneous fat,Regulation of lipid metabolism by regulating the expression of key genes of lipid metabolism in sheep.The regulation process may also be involved in the rumen microbial hydrogenation,fatty acid dehydrogenase and so on.This study has important practical significance for the regulation of meat quality and improvement of fat metabolism in grazing system.