COPPER AND MOLYBDENUM STATUS OF GROWING BEEF CATTLE IN A SELENIUM DEFICIENT AREA OF NORTHERN ONTARIO

Abstract

A study was conducted on the effect of nutritional muscular dystrophy (NMD) on the copper and molybdenum contents of various tissues from calves under three months of age. Fifty-one calves were employed from an area in northern Ontario where NMD is common and 12 calves from a dystrophy-free area. The latter animals were fed a milk substitute which contained some 4.5 times as much copper as the milk received by the calves in the NMD area. For suckled calves in northern Ontario, no significant difference in liver copper concentrations was observed between healthy and NMD-affected animals. In calves fed the milk substitute, the liver copper level was markedly higher [204.4 ± 71.0 (SD)] than in suckled calves with dystrophy (55.5 ± 36.3) or without the disorder (60.8 ± 53.7). The copper concentrations (μg/g DM) of other tissues from NMD-affected calves were: kidney 14.8 ± 3.3, heart 14.0 ± 2.5, lung 6.5 ± 2.0, spleen 4.3 ± 1.6 and muscle 3.0 ± 1.4. No significant differences in these copper levels occurred between NMD-affected and healthy calves, or those reared on the milk substitute. Similarly, there were no significant differences in tissue molybdenum concentrations. The data indicated that the calves reared in northern Ontario had a marginal copper deficiency. Tissue copper and molybdenum levels appeared to be unaffected by the development of myopathy in the calves. The copper status of two groups, of six calves each, wintered outdoors or indoors, also was compared. Hypocuprosis and copper plasma levels were not influenced by exposure to the severe outwintering conditions of northern Ontario. Plasma copper levels showed a gradual decrease from 66 ± 16 μg per 100 ml plasma at 1 week of age to 51 ± 10 μg per 100 ml at 19 weeks.