Comparison of Tri-Basic Copper Chloride Versus Copper Sulfate on Measures of Forage Utilization and Copper Status in Beef Heifers

The objective of this study was to investigate the effect of supplemental tribasic copper chloride (TBCC) vs Cu sulfate on the Cu status and voluntary forage intake of growing heifers fed forage-based diets. Twenty-four crossbred heifers were stratified by weight and randomly allotted to individual pens. Heifers were provided free-choice access to ground grass hay (8.0 and 54.0% CP and TDN, respectively) and 4.0 lb/d of a ground corn-cottonseed meal supplement. Three treatments were randomly allocated to pens, providing; 1) 100 mg/d Cu from Cu sulfate, 2) 100 mg/d Cu from TBCC, or 3) 0 mg Cu/d (Control). Forage intake was measured daily. Individual heifer body weight, jugular blood, and liver biopsy samples were collected on d 0, 30, 60, and 90. Heifer ADG was not affected by Cu treatment (average = 0.49 ± 0.15 lb/d). Change in liver Cu and plasma ceruloplasmin (Cp) concentration did not differ among Cu sources (120 vs 77 ppm liver Cu, -6.0 vs. 3.5 mg Cp/dL for Cu sulfate, and TBCC supplemented heifers, respectively). Heifers fed no supplemental Cu experienced a lesser accumulation of liver Cu and a greater decrease in Cp concentration over the 90-d supplementation period (-34.4 ± 20.6 ppm liver Cu and -4.1± 3.1 mg/dL Cp) compared to both Cu sulfate and TBCC supplemented heifers. Forage intake did not differ among Cu sources, however, heifers provided no supplemental Cu having lesser forage intake compared to both Cu sulfate and TBCC supplemented heifers (average forage intake = 10.8 and 11.7 lb/d for Control and Cu supplemented heifers, respectively). These data indicate that Cu sulfate and TBCC are of similar availability when offered to growing beef heifers in corn-cottonseed meal supplements. As well, these data indicate that the lack of supplemental Cu may decrease voluntary forage intake in growing beef heifers.