Studies of the toxicity of copper to pigs

Abstract

1. Six groups of four litter-mate female Large White pigs of about 17 kg live weight were allocated according to a 2×2 factorial design in each of two experiments in which rations containing 0 or 750 ppm copper were offered with either 0 and 500 ppm zinc, or 0 and 750 ppm iron. 2. Severity of toxicosis was assessed by determining aspartate transaminase activity in serum, observing the incidence of jaundice and determining the hemoglobin concentration in whole blood and Cu concentration in serum and liver. 3. Addition of 750 ppm Cu to the diet caused toxicity in nine out of twelve animals; it was most severe after about 4 weeks when two-to five-fold increases in serum Cu and aspartate transaminase levels were found and seven pigs were jaundiced. Serum Cu and aspartate transaminase concentrations and degrees of jaundice were apparently interrelated and returned to normal levels after 6 weeks, suggesting adaptation to the high Cu intake. Growth depression and a microcytic hypochromic anaemia persisted. 4. Addition of 500 ppm Zn or 750 ppm Fe in the presence of 750 ppm Cu eliminated jaundice and produced serum Cu and aspartate transaminase concentrations similar to control values after 4 weeks. Only supplementary Fe afforded protection against anaemia. 5. Variability in the response of the pig to Cu supplements could be partly due to variations in the intake of Fe and Zn. The addition of Fe and Zn supplements to pig diets supplemented with Cu would probably reduce the small risk of causing Cu poisoning.