Copper sulphate as a growth stimulant for pigs: effect of level and purity

Abstract

Two 2 × 4 factorial experiments each involved 8 litters of 8 pigs, one pig from each litter being allocated to each treatment. Diets containing supplements of a commercial grade of copper sulphate were compared with others containing Analar (Experiment 1) or micro-analytical reagent grade copper sulphate (Experiment 2). Four levels of each of two grades of CuSO4.5H2O, providing 16, 62, 125 or 250 p.p.m. Cu in the diets, were given in each experiment.The pigs were put on experiment at 8—9 weeks of age and most were slaughtered as their individual weights reached about 200 lb. The exceptions were 4 litters in Experiment 1 which were taken off experiment at that weight but not slaughtered. The pigs were fed in individual compartments, meal allowances being determined from a fixed scale based on live-weight.Purity of copper sulphate did not affect growth rate, feed conversion efficiency or carcass measurements in either experiment.Response to level of copper sulphate between about 45 and 100 lb. liveweight differed somewhat between experiments. In Experiment 1 pigs receiving 125 or 250 p.p.m. in the diet grew 4 or 9% faster and had better feed conversion efficiencies than those receiving 16 or 62 p.p.m. Cu. In Experiment 2, pigs receiving 62, 125 or 250 p.p.m. Cu all grew about 4–5% faster and had 1–5 % better feed conversion efficiencies than those receiving 16 p.p.m. Cu, but the effect on feed conversion efficiency was not statistically significant.Increase in copper sulphate above the trace level supplying 16 p.p.m. Cu in the diet had no effect on growth rate or feed conversion efficiency between 100 and 202 lb. live-weight or on killing-out percentage or carcass measurements.Comparison of the results with those from a previous experiment showed that in pigs fed according to a fixed scale the greatest consistent increases in growth rate and feed conversion efficiency have occurred with copper sulphate as 0·1% of the diet, giving 250 p.p.m. Cu. This supplement has only improved performance between 100 and 200 lb. live-weight in one experiment out of five.