Efficacy of a copper-lysine complex as a growth promotant for weanling pigs

Eight 28- or 35-d experiments involving 1,301 crossbred pigs weaned at 30 [+ or -] 2 d of age (7.0 to 7.9 kg initial weight) were conducted to evaluate the efficacy of a Cu-lysine complex (CuLys; CuPLEX 80[TM] in Exp. 1 to 5, and CuPLEX 100[TM] in Exp. 6 to 8) at dietary concentrations of 50, 100, or 200 ppm as a growth promoter for weanling pigs. CuPLEX 80 contained 50% Cu in the complexed form (1 mol Cu:2 mol lysine) and 50% Cu as CuS[O.sub.4][center dot]5[H.sub.2]O (CuS[O.sub.4]). All the Cu in CuPLEX 100 was in the complexed form. In general, the addition of Cu from CuS[O.sub.4] or either CuLys source improved pig performance. Overall, averaged across Cu sources, there were no differences between 100 and 200 ppm of Cu in the magnitude of improvement over controls for daily gain (14.0 vs 14.3%), daily feed (12.1 vs 10.7%), or feed:gain ratio (1.6 vs 3.0%). Averaged across levels of Cu supplementation, the percentage improvements from CuLys additions were greater than those for CuS[O.sub.4] for growth rate (16.8 vs 11.5%; P [is less than] .03) and feed intake (14.1 vs 8.7%; P [is less than] .01), but not for efficiency of feed utilization (2.2 vs 2.4%). These trends were similar for both sources of CuLys. Liver Cu concentrations of pigs receiving 200 ppm of Cu in the totally complexed form (CuPLEX-100) were lower (P [is less than] .025) than concentrations in those receiving 200 ppm of Cu from CuS[O.sub.4] (111 vs 221 ppm). Based on these results, the Cu-lysine complex was as effective as, and in some cases more effective than, CuS[O.sub.4] in enhancing pig performance and resulted in lower liver Cu stores. Also, 100 ppm of Cu was as efficacious in stimulating growth as 200 ppm of Cu, regardless of source of Cu.