Effect of high dietary copper on somatostatin and growth hormone-releasing hormone levels in the hypothalami of growing pigs.

This experiment was conducted to examine the effect of dietary copper supplementation on somatostatin (SS) and growth hormone-releasing hormone (GHRH) mRNA expression levels in the hypothalami of growing pigs. A total of 45 crossbred pigs were randomly assigned to three groups of 15 pigs each; five replicates of three animals comprised each group. Pigs were allocated to diets that contained 5 mg/kg copper (control), 125 mg/kg copper sulfate, or 125 mg/kg copper methionine. At the end of the experiment, five pigs were selected at random from each group and slaughtered, and hypothalami were collected for determination of SS and GHRH mRNA expression levels. The results showed that the SS expression levels were lower and the GHRH levels were higher in pigs fed the diets with 125 mg/kg copper methionine (P<0.05) and 125 mg/kg copper sulfate (P<0.05), respectively, than in pigs fed the diet with 5 mg/kg copper. Furthermore, the relationship between SS mRNA and GHRH mRNA abundance had a significantly negative correlation (P<0.05). The data indicated that high dietary copper could enhance GHRH mRNA expression levels and suppress SS mRNA expression levels in the hypothalami of pigs. High lever dietary copper (125 mg/kg copper sulfate or 125 mg/kg copper methionine) increased pigs' growth performance and feed efficiency but had no significant effect on daily feed intake; 125 mg/kg copper sulfate or 125 mg/kg copper methionine at the same lever had no difference on growth promoting in pigs.