Effect of a high copper intake and different levels of molybdenum on the health of sheep.

Molybdenum at levels of 2, 20, 40, and 60 mg/kg dry matter was added to a sheep ration containing 82 copper and 3, 8 g sulphur per kg dry matter. At the 2 higher levels of molybdenum, a substantial accumulation of copper and molybdenum was observed in the kidney cortices of the South African Mutton Merinos (reported elsewhere). The effect of these treatments on the health of the sheep was investigated. Observations on the 3 molybdenum supplemented treatments were: Serum enzyme levels remained normal throughout the trial. No evidence of kidney damage due to treatment could be obtained from kidney clearance studies. No pronounced liver lesions were evident from histophathological evaluations. A significant increase in Periodic acid Shiff positive stained granules was observed in the cortical tubules of the kidneys at increased molybdenum intakes. However, this was considered to be of minimal physiological significance. It was concluded that molybdenum prevented liver damage due to excess copper and that copper and molybdenum which did accumulate in the kidneys were probably harmless and present in an unavailable form to the body or caused minimal morphological changes. No haemolytic crisis occurred in the sheep receiving no added molybdenum. However, their concentration of serum enzymes Aspartate transaminase and Lactate dehydrogenase increased throughout the 193 day trial. It is suggested that elevated levels of these enzymes may be unreliable indicators of an approaching haemolytic crisis in the Merino.