The Effect Of Dietary Copper Supplementation On Feed Intake In Weanling Pigs And Its Mechanism

The current study evaluated gene expression of appetite regulators in hypothalamus and levels of appetite regulating hormones in plasma in response to copper supplementation to investgate the effects of high dietary copper on the feed intake of weanling pigs and the underlying mechanism.100 crossbred pigs were randomly assigned to one of four groups with five replicates,based on body weight and gender.Cu was supplemented at the levels of 10,100,175 and 250 mg/kg in form of CuSO₄.Feed intake and weight gain were determined.On d 21 of the experiment 1 pig from each replicate was slaughtered and the hypothalami was collected for determining mRNA expression levels of appetite-regulating genes.Blood samples were also collected for determination of hormone levels.The results showed that average daily feed intake(ADFI) and average daily gain (ADG) were higher(P＜0.05) in 250 and 175,250 mg/kg copper-supplemented groups than in the control group.Feed:gain(F:G) ratio was lower in pigs fed the diets with 250 mg/kg copper(P＜0.05) than in the control group.250 mg/kg copper supplemention tended to increase copper concentration in the hypothalamus (P=0.053),while the concentration of zinc and iron were not affected(P＞0.05). Furthermore,The abundance of NPY mRNA in hypothalamus was higher in 250 mg/kg copper-supplemented group(P＜0.05),whereas the abundances of POMC and long-form Leptin receptor mRNA were significantly reduced in 175,250 mg/kg and 100,175,250 mg/kg copper-supplemented groups respectively(P＜0.05).No differences were found for AMPKα2 subunit,melanocortin-4 receptor(MC4R),orexin, type 2 orexin receptor mRNA expression(P＞0.05).Both Leptin and insulin levels in the plasma were numerically elevated by copper supplementation(P＞0.05).These data suggest that copper has a stimulative effect on feed intake of weanling pigs which plays a pivotal role to elevate growth performance.Furthermore,the down-regulation of long-form Leptin receptor mRNA expression might contribute to the stimulation of high dietary copper supplementation via regulation of NPY and POMC mRNA expression.