Broiler responses to copper levels and sources: growth, tissue mineral content, antioxidant status and mRNA expression of genes involved in lipid and protein metabolism.

Abstract

BACKGROUND: Five hundred 8-d old male broilers Cobb500 were randomly allotted into 10 treatments in factorial arrangement with 5 Cu levels (0, 4, 8, 12, and 16&#xa0;mg/kg), and 2 sources (Cu proteinate, CuPro and Cu sulphate, CuSO4.5H2O) for a 10-d-experiment. RESULTS: Feed conversion ratio (FCR) was better (P&#x2009;<&#x2009;0.05) in CuPro fed chicks compared with CuSO4.5H2O group. Average daily feed intake (ADFI) decreased linearly (P&#x2009;<&#x2009;0.05) as dietary Cu increased. A quadratic response (P&#x2009;<&#x2009;0.05) to&#xa0;Cu levels was found for FCR, being optimized at 9.87 and 8.84&#xa0;mg Cu/kg in CuPro and CuSO4.5H2O diets, respectively. Copper supplementation linearly increased liver Cu content (P&#x2009;<&#x2009;0.05) and tended to linearly increase (P&#x2009;=&#x2009;0.07) phosphorus (P) and copper in tibia. Manganese and zinc were higher (P&#x2009;<&#x2009;0.05) in tibia of CuPro fed birds. Broilers fed CuPro exhibited lower liver iron (P&#x2009;<&#x2009;0.05) content, lower activities of Cu, Zn superoxide dismutase (CuZnSOD) in breast muscle and liver, and glutathione peroxidase in liver. Glutathione peroxidase reduced linearly (P&#x2009;<&#x2009;0.05) with CuPro levels and increased linearly (P&#x2009;<&#x2009;0.05) with CuSO4.5H2O levels and were lower (P&#x2009;<&#x2009;0.05) in all CuPro levels in breast muscle. Breast muscle malondialdehyde concentration tended to be higher (P&#x2009;=&#x2009;0.08) in broilers fed CuSO4.5H2O. Copper levels linearly increased (P&#x2009;<&#x2009;0.05) metallothionein (MT) and malate dehydrogenase (MDH) expression in liver, and six-transmembrane epithelial antigen of the prostate-1 (STEAP-1) in the intestine. Copper elicited a quadratic response (P&#x2009;<&#x2009;0.050) in AKT-1 and mammalian target of rapamycin (mTOR) in breast muscle, CuZnSOD in liver and antioxidant 1 copper chaperone (ATOX 1) in intestine. Broilers fed CuPro exhibited higher mRNA expression of mTOR in muscle breast and lower CuZnSOD in liver and ATOX 1 in intestine. Interaction (P&#x2009;<&#x2009;0.05) between levels and sources was found in mRNA expression for GSK-3&#x3b2;, MT, and CuZnSOD in breast muscle, FAS and LPL in liver and MT and CTR1 in intestine. CONCLUSIONS: CuPro showed beneficial effects on&#xa0;feed conversion and bone mineralization. Organic and inorganic Cu requirements are 9.87 and 8.84&#xa0;mg Cu/kg, respectively.