Effects of Source and Level of Copper on Performance and Liver Copper Stores in Weanling Pigs

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Abstract
Five 28- to 33-d experiments involving 460 crossbred pigs weaned at 28 ± 2 d of age (initial weight, 6.7 to 8.1 kg) were conducted to determine the effects of feeding high dietary levels of Cu sulfate (CuSO4) or Cu oxide (CuO) on rate and efficiency of gain and liver Cu stores of weanling pigs. The pigs were housed in groups of five to six/pen and fed a fortified, unmedicated, corn-soybean meal-dried whey basal diet (1.1% lysine, 30 ppm Cu). In Exp. 1 and 2, pigs (eight replicates) were fed the basal or the basal plus 125 or 250 ppm Cu from CuSO4 or CuO for 28 d. In Exp. 3 and 4, four replications were fed the same diets as in Exp. 1 and 2 plus two additional diets (500 ppm Cu from CUSO4 or CuO). In Exp. 5, dietary levels of 0, 125, 250, 375 or 500 ppm Cu from CuSO4 were evaluated using four replications. At the end of each experiment, the liver from one pig in each pen was collected for Cu analysis. Overall, rate and efficiency of gain were improved (P < .01) by feeding 125 or 250 ppm Cu as CuSO4, with the 125 ppm dietary level being about 75% as effective in stimulating growth as 250 ppm. Performance of pigs was not different from controls when the highest (500 ppm) level of Cu (from CuSO4) was fed. Liver Cu increased 10- to 70-fold when 250 to 550 ppm Cu from CuSO4 was included in the feed. Withdrawal of 500 ppm dietary Cu for 28 d decreased in liver Cu from 1,513 to 274 ppm of DM. All dietary levels of CuO failed to influence performance or liver Cu levels, suggesting that the Cu in CuO was largely unavailable and ineffective as a growth promotant for weanling pigs.