Bioavailability of copper from copper glycinate in steers fed high dietary sulfur and molybdenum

¹ Department of Animal Science, North Carolina State University, Raleigh, NC 27695
² Pancosma, S. A., Geneva, Switzerland

^* To whom correspondence should be addressed. E-mail: Jerry_Spears{at}ncsu.edu.

	Abstract

Sixty Angus (n = 29) and Angus-Simmental cross (n = 31) steers, averaging 9 mo of age and 277 kg initial BW, were used in a 148-d study to determine the bioavailability of copper glycinate (CuGly) relative to feed grade copper sulfate (CuSO₄) when supplemented to diets high in sulfur (S) and molybdenum (Mo). Steers were blocked by weight within breed and randomly assigned to 1 of 5 treatments: 1) control (no supplemental Cu), 2) 5 mg Cu/kg of DM from CuSO₄, 3) 10 mg Cu/kg of DM from CuSO₄, 4) 5 mg Cu/kg of DM from CuGly, and 5) 10 mg Cu/kg of DM from CuGly. Steers were individually fed a corn silage-based diet (analyzed 8.2 mg Cu/kg of DM), and supplemented with 2 mg Mo/kg of diet DM and 0.15% S for 120 d (Phase 1). Steers were then supplemented with 6 mg Mo/kg of diet DM and 0.15% S for an additional 28 d (Phase 2). Average daily gain and G:F were improved by Cu supplementation regardless of source (P = 0.01). Final ceruloplasmin, plasma Cu, and liver Cu values were greater (P < 0.05) in steers fed supplemental Cu compared with controls. Plasma Cu, liver Cu, and ceruloplasmin values were higher (P < 0.05) in steers supplemented with 10 mg Cu/kg of DM vs. those supplemented with 5 mg Cu/kg of DM. Based on multiple linear regression of final plasma Cu, liver Cu, and ceruloplasmin values on dietary Cu intake in Phase 1 (2 mg Mo/kg of DM), bioavailability of Cu from CuGly relative to CuSO₄ (100%) was 140 (P = 0.10), 131 (P = 0.12) and 140% (P = 0.01), respectively. Relative bioavailability of Cu from CuGly was greater than from CuSO4 (P = 0.01; 144, 150, and 157%, based on plasma Cu, liver Cu, and ceruloplasmin, respectively) following supplementation of 6 mg Mo/kg of DM for 28 d. Results of this study suggest that Cu from CuGly may be more available than CuSO₄ when supplemented to diets high in S and Mo.

Key Words: bioavailability, cattle, copper glycinate, copper sulfate, growth

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