Copper supplementation of pig diets. The effect of protein level and zinc supplementation on the response to added copper

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Abstract
1. Five hundred and fifty-two pigs were used in an experiment having six treatments. High and low protein rations were given (a) unsupplemented, (b) supplemented with 0·1% copper sulphate (CuSO4·5H2O) and (c) supplemented with 0·1% copper sulphate and 0·025% zinc carbonate (ZnCO3).2. Performance was significantly reduced and 18 pigs died from copper toxicosis, when the low protein ration supplemented with copper sulphate was fed.3. There were no indications of toxicity and performance was equal to the controls when the low protein diet supplemented with copper and zinc was fed.4. The addition of copper to the high protein diet slightly reduced performance and six pigs died from copper toxicosis.5. The addition of copper and zinc to the high protein diet improved growth rate and eliminated the toxicity associated with copper supplementation.6. No significant treatment effects on haemoglobin or packed cell volume were observed, other than a small effect of protein level on PCV.7. Copper supplementation of the diets significantly increased liver and kidney copper levels and liver zinc levels. It reduced liver and kidney iron contents. The addition of copper and zinc to the diet reduced the increase in liver copper associated with copper supplementation, and increased the level of zinc in both livers and kidneys.