Copper toxicity in sheep
Palm kernel meal contains 20-30 ppm of copper (APOC, 2006). Sheep are very sensitive to copper and levels as low as 25 ppm in the diet can be toxic to them (Schoenian, 2009). If palm kernel cake is fed to excess (90% of the diet) to sheep, it is known to cause chronic copper toxicity and death due to hepatic necrosis. When palm kernel cake is fed at lower levels (60% of the diet) to rams, it results in spermatogenesis problems and other reproduction deficiencies (Yaakub et al., 2009). Supplementing diets with sodium molybdate may alleviate copper toxicity since Mo forms insoluble complexes with Cu and prevents copper absorption (Schoenian, 2009; Akpan et al., 2005). Zinc is another antagonist to copper absorption but zinc supplementation may result in high zinc concentration in blood, liver and kidneys. Phytase supplementation may be a complementary way of preventing copper toxicity as it enhances zinc availability in sheep (Akpan et al., 2005).