| The experiment was conducted to assess the effect of dietary supplementation of Cu on the growth performance,digestive enzymes,tissue mineral contents and absorptive transporters in small intestinal mucosa of weanling pigs.One hundred crossbred pigs weaned at 28±2 d of age were assigned randomly to one of the four treatments with 5 replicates(pens) per each treatment.Pigs were fed corn-soybean-extruded soybean meal diet.The diets were supplemented with Cu in the form of CuSO4·5H2O at levels of 10,100, 175,250 mg/kg to create a one-factorial arrangement of treatments.Digestive trial was conducted for 4 d on d 17,18,19,20 of the experiment.One pig from each pen was slaughtered on d 21 of the experiment.The results showed that supplementing diet with 250 mg/kg Cu had a positive effect on averge daily gain(P＜0.05),daily feed intake(P＜0.05) and ratio of gain/feed(P＜0.05). The regression equations of ADG(y1,g),ADFI(y2,g)and G:F(y3) with the copper level(x, mg/kg) during the experiment:y1=155.25+0.911x-1.40×10-3x2(R2=0.9940,P=0.055), y2=379.92+0.951x-4.36×10-4x2(R2=0.9911,P=0.094) and y3=0.402+1.23×10-3x-3.33×10-6 x2(R2=0.8897,P=0.332).Compared to the level of 10 mg/kg Cu,higher supplementing levels had significant effect on the apparent digestibilities of CP(P＜0.05) and EE(P＜0.05).The regression equations of CP(y1,%),EE(y2,%) with the copper level(x,mg/kg):y1=66.79+8.23×10-2x -1.62×10-4 x2(R2=0.9730,P=0.164) and y2=66.35+0.070 x -9.89×10-5 x2(R2=0.99952,P =0.069).The supplementation of Cu improved amylase and lipase activities in jejunual content (P＜0.05) and lipase in pancreas(P＜0.05).Cu supplementation had no effect on intestinal morphology.Supplementing 250 mg/kg significantly elevated the DMT1(divalent metal transporter) mRNA abundance in duodenum mucosa.However,there's no positive effect (P＞0.05) of Cu supplementation on PepT1(peptide transporter 1) and SGLT1(sodium/ glucose cotransporter) mRNA abundance in intestinal mocosa. The supplementation of Cu had significant effect on Cu excretion in feces(P＜0.01). The liver Cu content elevated approximately 4-fold in pigs fed diet with 250 mg/kg Cu compared with pigs fed diet with 10 mg/kg Cu,no increases were observed in pigs receiving the lower level of Cu(100 and 175 mg/kg).Both the Fe and Zn contents in liver, kidney and feces were not affected by Cu supplementation.The copper content of feces,liver,kidney had significant positive correlation with the copper level(P＜0.01),respectively.A positive correlation was observed between DMT1 gene abundance and copper level(P＜0.05).The copper content of feces was a significantly correlated with the copper of liver and kidney and the abundance of DMT1(P＜0.01).The copper content of liver was positively related to the copper content of kidney(P＜0.05) and a positive correlation trend with the abundance of DMT1(P=0.067).The regression equations of the copper content in the feces(y1,mg/kg),liver(y2,mg/ kg) and kidney(y3,mg/kg) with the copper level(x,mg/kg):y1=21.93+4.40x +4.39×10-3x2(R2=0.9999,P＜0.01),y2=4.74x1.023(R2=0.9991,P＜0.01),y3=26.46+9.92x 10-2 x+ 4.47×10-4x2(R2=0.9829,P=0.164).The regression equations of DMT1 gene abundance(y) with the copper level(x,mg/kg):y=4.86+5.49×10-2x+3.37×10-7x2(R2=0.9617,P=0.196).These results suggested that dietary supplementation with 250 mg/kg Cu could improve growth performance,nutrient digestibilities and intestinal enzyme activities,but increase Cu excretion from feces and deposition in the liver and kidney for weanling pigs.
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