Effect of dietary copper sources on performance, gastric ghrelin-RNA expression, and growth hormone concentrations in serum in piglets.

Two performance studies were conducted to investigate the effects of 3 different sources of Cu on production parameters of piglets. A total of 256 piglets weaned at 24 ± 2 d were randomly allocated into 4 treatments with 10 or 8 replicates per treatment of 4 or 3 piglets per pen in Exp. 1 and 2, respectively. The experimental period was divided into 3 feeding phases: Phase 1 (24 to 35 d), Phase 2 (36 to 49 d), and Phase 3 (50 to 70 d). Treatments included a Control group (fed 10 mg/kg of Cu from CuSO4), a group fed 160 mg/kg of either CuSO4 (CuSO4-160) or tri-basic copper chloride (TBCC), and a group fed Cu methionine hydroxy analogue chelated (Cu-MHAC) at 150, 80, and 50 mg/kg in Phases 1, 2, and 3, respectively. The methionine value of Cu-MHAC was accounted during diet formulation to achieve the same levels of methionine across treatments. Phases 1 and 2 diets contained 2,200 and 1,500 ppm of ZnO, respectively; and antibiotics were used as growth promoters. Performance parameters were analyzed as completely randomized block design, in which each experiment was considered as a block. In trial 2, blood serum and mucosal samples, from the fundic region of the stomach, were collected from 1 piglet per replicate at day 70 and tested for serum growth hormone levels (GH) and ghrelin mRNA expression, respectively. The contrast between Cu-MHAC vs. CuSO4-160 + TBCC showed that piglets fed Cu-MHAC exhibited better feed conversion ratio (FCR) in all feeding phases compared with feeding inorganic Cu (P < 0.05). Overall, feeding Cu-MHAC improved body weight (BW), BW gain, feed intake (FI), and FCR vs. Control diet fed piglets; yet, it improved BW and FCR vs. TBCC fed piglets, and improved BW, BW gain, and FI vs. CuSO4-160 fed piglets (P < 0.05). Feeding TBCC promoted similar performance than feeding CuSO4-160, regardless of age (P > 0.05). Both ghrelin expression and growth hormone serum levels were significantly increased by feeding Cu-MHAC vs. Control diet fed animals (P < 0.01). Feeding CuSO4-160 upregulated ghrelin expression vs. Control (P < 0.01) while GH serum levels and ghrelin expression did no change by feeding TBCC compared with Control diet fed animals (P > 0.05). It was concluded that feeding Cu-MHAC at the levels tested herein can improve growth performance of piglets beyond feeding 160 ppm of either CuSO4 or TBCC, which may be partially explained by the increased expression of ghrelin and GH serum levels.