EXPERIMENTALLY-INDUCED CHRONIC COPPER TOXICITY IN CATTLE

Eight Bonsmara bulls and eight Bonsmara heifers, having masses of betw een 210 and 266 kg when selected, were randomly allocated to four grou ps, each comprising two bulls and two heifers. Group 1 received 0,6 mg of copper (Cu)/kg of body mass per day (bm/d), group 2, 10 mg of Cu/k g of bm/d and group 3, 20 mg of Cu/kg of bm/d as a copper sulphate sol ution, given orally, 5 d a week over 745 d. Group 4 was the control gr oup. One bull from group 3 was euthanased on day 679 of the trial, a h eifer from group 3 and a bull from group 2, on day 695 of the trial, a nd a heifer from group 2, on day 731 of the trial, after they had show n clinical signs. During the course of the trial, clinical signs, seru m gamma glutamyltransferase and aspartate aminotransferase activity, b lood urea nitrogen, and plasma copper, zinc and iron concentrations we re monitored. Live mass was recorded weekly to determine any effect on mass gain. The liver and kidney copper, zinc, iron and manganese conc entrations at the time of death or slaughter are given. From the resul ts it was concluded that subclinical damage to the liver and eventual copper toxicity can occur when cattle are continually exposed to oral doses greater than or equal to 12 mg of Cu/kg of bm/d. It was also con cluded that cattle can probably tolerate oral doses of less than or eq ual to 0,6 mg of Cu/kg of bm/d for an indefinite period, provided ther e are no other sources of copper, such as may occur with air-pollution , or provided no other adverse mineral interactions occur, such as may occur with molybdenum deficiency.