EFFECT OF DIETARY PROTEIN SOURCE ON COPPER TOXICITY IN EARLY-WEANED PIGS

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Abstract
Thirty-two 3-week-old pigs (16 males and 16 females) were used to study the effect of major dietary protein source on toxicity to high levels of supplemental copper. Fish meal (FM) or soybean meal (SBM) diets containing 0, 250, 500 or 750 ppm added Cu were fed for 6 weeks. Additions of 500 and 750 ppm Cu to the FM diet depressed (P < 0.05) weight gain and feed intake, whereas similar additions to the SBM diet had no appreciable effect. Tissue, especially liver and kidney, and serum Cu levels increased with level of added dietary Cu, irrespective of dietary protein source. Cu concentrations tended to be slightly higher for pigs fed the Cu-supplemented FM diets than for those fed the Cu-supplemented SBM diets but, unlike weight gain, there were no pronounced protein source × dietary Cu level interactions for tissue or serum Cu concentrations. Serum Cu levels tended to increase with length of time the pigs were on experiment, especially for animals fed the diets containing 500 and 750 ppm added Cu. Serum aspartate: 2-oxoglutarate aminotransferase (SGOT) activity appeared to be unrelated to dietary treatment. No gross pathological changes were found in the tissues of animals slaughtered at the conclusion of the experiment.