Effects Of Dietary Energy Level On Fatty Acid Composition And Related Gene Expression In Body Tissue Of Meat Donkey

This thesis mainly studied the influence of dietary energy level on fatty acid composition of meat donkey body tissue,and explored its influence mechanism from the aspects of blood,liver and body tissue lipid metabolism related enzyme activities and gene expression.The research results provide a theoretical basis for the formulation of energy and nutrition needs of donkey meat and the improvement of fatty acid composition and nutritional value of donkey meat through nutritional regulation.This thesis is mainly divided into three experiments.The single factor completely randomized design was used in this study.Thirty six meat donkeys(male)aged 1 year old with similar weight(150±25kg)were selected and randomly divided into three treatment groups: low energy group(E1),medium energy group(E2)and high energy group(E3),each treatment group had 4 replicates and each replicate had 3 donkeys.They were fed diets with different energy levels.The experimental period included 10 days of pre-test period and 135 days of normal test period,which were divided into early stage(1-45 days),middle stage(46-90 days)and late stage(91-135 days).During the experiment,blood was collected and weighed every 15 days,after 12 hours of fasting and 2 hours of water deprivation,all donkeys were slaughtered to collect liver,longissimus thoracis muscle,semitendinosus muscle,triceps brachii muscle and gluteal muscle,subcutaneous adipose tissue,mesentery fat,omentum fat and kidney fat.Experiment 1 mainly studied the effect of dietary energy level on fatty acid composition in muscle and fat tissue of donkey.The results show that: compared with E1 group,E2 and E3 groups increased the content of C18:3n3,C20:3n3,n-3PUFA,C18:2n6c,C18:3n6,n-6PUFA in most muscle and adipose tissues,and decreased the content of C17:0 and the value of n-6/n-3.The distribution of PUFA,n-6PUFA,C16:0and C18:2n6c in muscle and adipose tissue was similar,but the distribution of MUFA,n-3PUFA,C18:1n9c,C18:3n3,U/S and P/S in adipose tissue was higher than that in muscle tissue,the distribution of SFA,n-3LCPUFA,n-6LCPUFA,C20:5n3,C22:6n3and n-6/n-3 was opposite.The most abundant fatty acids in SFA,MUFA,PUFA and n-3PUFA were C16:0,C18:1n9c,C18:2n6c and C18:3n3,respectively.Compared with beef and mutton,donkey meat has the characteristics of high PUFA,high n-6PUFA,high C18:3n3,high C18:2n6c and low SFA.experiment 2 mainly studied the effects of different energy levels in diets on related indexes of blood lipid metabolism and liver fatty acid composition of donkeys.The results show that: compared with the E1 group,the contents of serum CHOL before and after fattening,serum HDL-C in early fattening and serum GLU in late fattening were increased in groups E2 and E3,while the contents of serum TG in early and middle fattening and serum NEFA in middle and late fattening were decreased in groups E2 and E3.Compared with E1 or E2 groups,serum HDL-C in E3 group increased in middle and late period of fattening,serum LDL-C,CHOL,GLU in middle period of fattening and serum TG in late period of fattening,while serum D3 HB content in the whole period of fattening decreased in E3 group.E2 group increased CHOL content in longissimus thoracis muscle and decreased CHOL content in subcutaneous adipose tissue;E2 and E3 groups decreased CHOL content in triceps brachii muscle and gluteal muscle,especially in E3 group.Group E3 increased the CHOL content of kidney fat,while group E2 decreased the CHOL content of omentum fat.In addition,E3 group increased the contents of n-3PUFA,C18:3n3,C20:3n3,n-6PUFA,C18:2n6c and PUFA in plasma and liver,increased the contents of C18:1n9t,C20:5n3,C20:2n6,n-6LCPUFA and U/S,P/S in liver,and decreased the contents of SFA.Experiment 3 mainly studied the effects of dietary energy levels on the activities of enzymes related to lipid metabolism and gene expression in meat donkey tissues.The results show that: compared with E1 group,E3 group increased the activity of ACC,LPL,FAS,SCD,ELOVL5,SLC27A4 in Donkey Serum,but decreased the activity of HSL.The E2 and E3 groups increased the m RNA expression of PPARγ in the longissimus thoracis muscle,subcutaneous adipose tissue and liver;improve the activity and m RNA expression of ELOVL5 and LPL in the longissimus thoracis muscle;improve the activity of ACC,SCD,FAS,LPL in subcutaneous adipose tissue and its m RNA expression;improve the activity of FAS and ELOVL5 in the liver,their m RNA expression and FADS1 m RNA expression,reduce the activity of HSL and its m RNA expression in liver and subcutaneous adipose tissue.In conclusion,diets with medium and high energy levels up-regulating the gene expression of PPARγ in the liver,subcutaneous adipose tissue and longissimus thoracis muscle,the activity and gene expression of ELOVL5 and FADS1 in the longissimus thoracis muscle and liver,increased the content of C18:3n3,C20:3n3,n-3PUFA,C18:2n6c,PUFA in plasma and liver,thereby increase the content of C18:3n3,C20:3n3,n-3PUFA,C18:2n6c,C18:3n6,n-6PUFA in the majority tissues of meat donkeys,and reduce n-6/n-3.