Dietary copper supplementation modulates performance and lipid metabolism in meat goat kids

Forty-eight male Lezhi black goat kids with similar body weight((12.09±1.70)kg)and age((60±5)d)were used to determine the effect of dietary copper(Cu),in the form of reagent grade Cu sulfate(CuSO4∙5H2O),on performance,serum lipid profile,and the relative mRNA abundance of genes involved in lipid metabolism.Goat kids were stratified by body weight and randomly assigned to one of 4 treatment groups.Each treatment consisted of 12 replicate pens with each pen containing one goat kid.Treatment groups received the basal diet with no supplemental Cu(control),basal diet plus 10 mg of Cu kg^(-1)of dry matter(DM),basal diet plus 20 mg of Cu kg^(-1)of DM,or basal diet plus 30 mg of Cu kg^(-1)of DM.Goats were housed individually in pens and fed a high-concentrate pelleted diet for 60 d.Average daily gain,average daily feed intake and feed:gain of goats were not affected by dietary Cu supplementation(P>0.10).No differences were detected in serum total cholesterol,triglyceride,and high density lipoprotein cholesterol concentrations of goat kids fed with different Cu concentrations(P>0.05).However,serum low density lipoprotein cholesterol concentrations decreased linearly(P=0.01)as the concentration of dietary Cu increased.Intramuscular fat content of longissimus muscle increased(P=0.002)quadratically and liver Cu concentrations increased(P<0.001)linearly as dietary Cu concentration increased.Compared with the control,dietary supplementation of 20 mg Cu kg^(-1)DM decreased the relative mRNA abundance of fatty acid-binding protein 4(P=0.01)and lipoprotein lipase(P=0.05),and tended to decrease the relative mRNA abundance of carnitine palmitoyltransferase I(P=0.06)in longissimus muscle of goats.The relative mRNA abundance of peroxisome proliferator-activated receptor alpha(P<0.001),carnitine acetyltransferase(P=0.001),and carnitine palmitoyltransferase Ⅰ(P=0.001)were also decreased in liver by Cu supplementation.These results indicate that dietary supplementation of Cu modified lipid metabolism by increasing muscular fat and decreasing serum low density lipoprotein cholesterol,and the modification might be associated with the reduction of relative mRNA abundance of genes for oxidation of long-chain fatty acid in muscle and liver of Lezhi black goat kids.