Dietary zinc treatment for chronic copper intoxication in palm kernel cake (PKC) fed sheep

Thirty, 4 month-old male Maim x Polled Dorset crossbred sheep were allocated into 6 groups of 5 animals each. Four groups of animals were stall-fed with basal diet of 90% palm kernel cake (PKC) and 10% grass (G) for 16 weeks. One group of the animal was slaughtered at the end of the 16 weeks feeding trial (PKC group), whilst the other three groups were further fed with either the same diet (PKC+PKC group) or fed with a new diet consisting of 30% corn and 10% fish meals (CF) and grass (60%) either with (PKC+CF+Zn group) or without (PKC+CF group) zinc supplementation (500 mg/g Zn as zinc sulfate) for another 16 weeks and were slaughtered at the end of the feeding trial, The other two groups which act as controls were fed with corn (30%) and fish meals (10%) and grass (60%), and were slaughtered at weeks 16 (CF group) and 32 (CF+CF group) of the trial. The blood, right and left liver, renal cortex and medulla, pancreas, bile and urine of all animals were analysed for copper and zinc contents using an atomic absorption spectrophotometer. The liver and kidney were also fixed in 10% buffered formalin for histopathological examination. The study showed that neither clinical signs nor gross lesions of copper or zinc toxicity were observed throughout the trial. However, the copper concentration in both the right and left liver of PKC fed sheep at weeks 16 and 32 rose to about 3 times that of the controls and remained high in both the PKC+CF and PKC+CF+Zn groups. A similar pattern of copper concentration was observed in the blood. The copper and zinc contents in the renal cortex and medulla, pancreas, bile and urine remained low in all groups. The zinc content in the liver of PKC+CF+Zn group was significantly increased. Histologically, moderate hepatic lesions were observed in the PKC fed sheep at week 32. The lesions were milder in the other groups especially in the PKC+CF+Zn group. No significant renal lesions was recorded in all groups. It was concluded that the usage of dietary zinc supplementation (500 mg/g) in the treatment of PKC toxicity in sheep was unsatisfactory. The ability of Malin x Polled Dorset crossbred sheep to tolerate the high copper content in PKC at least during the first 16 weeks of the feeding trial may provide more avenue in the utilization of PKC as a major feed ingredient in sheep.