Copper supplementation of Canadian diets for growing-finishing pigs

A co-operative trial involving 10 swine units and 744 pigs examined the effects of adding 0.05 and 0.08% copper sulfate to diets fed, ad libitum, from approximately 11 to 90 kg liveweight. Supplementation resulted in weighted improvements of 2.2 and 1.7% in growth rate and 2.0 and 2.2% in the efficiency of feed conversion, respectively, for the overall period. Added copper had little effect upon carcass characteristics, but resulted in a marked increase in liver copper concentrations. Although 31 of the 500 livers analyzed contained levels in excess of the Canadian tolerance (150 mg Cu/kg fresh weight), 28 of these were from pigs fed the 0.08% copper supplement. Pigs fed the copper-supplemented diets tended to have a more unsaturated backfat, which contained a lower proportion of stearic acid, but more palmitoleic acid and a higher oleic:stearic ratio. There was evidence that both the composition of the unsupplemented diets and the sex of the pigs could also significantly influence the criteria measured in the carcass tissues. The level of dietary copper did not affect the eating quality of pork held for 4 or 8 mo frozen storage. The results indicate that under Canadian conditions, it would be preferable to limit the use of high levels of copper to diets for pigs under 50 kg liveweight.