Mineral balance of finishing pigs fed copper sulfate or a copper-lysine complex at growth-stimulating levels.

Twenty-four crossbred barrows (average BW, 70.8 kg) were used to compare the digestibility of dry matter and the mineral absorption and retention by pigs fed two Cu sources. Dietary treatments were 1) basal (B) (16% CP corn-soybean meal-based diet, 36 mg/kg of Cu), 2) B + 200 mg/kg of Cu from CuSO4.5 H2O (CuSO4), and 3) B + 200 mg/kg of Cu from a copper lysine complex (CuLys). All diets contained equal lysine content and .05% chromic oxide for indirect determination of absorption. Two 7-d total collection periods were conducted. Pigs were fed 8% of metabolic BW (BW.75) divided into two equal feedings. Average daily gain tended to be higher for pigs fed CuLys than for pigs fed CuSO4 (P < .02). Dry matter digestibilities were similar (P > .10) among treatments. The absolute amount of Cu absorbed and retained was greater for pigs fed both Cu sources (P < .001) than for pigs fed the control diet. Iron and Zn intake and excretion and the percentage of Fe absorbed and retained were similar (P > .10) among treatment groups. Chromium intake and excretion in feces were not different (P > .10), with an average recovery of 93.8%. Indirect DM digestibility was similar to total collection values; however, mineral values were similar only after correction for Cr recovery. Pigs fed elevated Cu absorbed more Cu, with no difference between the two sources. Zinc and Fe absorption and retention were generally not affected (P > .10) by Cu addition or sources. The absorption and retention of Cu was similar for pigs fed growth-stimulative levels of Cu from CuSO4 or copper lysine complex.