Copper deficiency in ruminants in the South East of South Australia

Abstract

Pasture development in the South East of South Australia has depended upon trace element enriched fertiliser applications. Despite the wide usage of copper-enriched fertilisers, copper deficiency is still evident in livestock at pasture, particularly cattle. Serum collected from cows and heifers during the systematic sampling program of the Brucellosis and Tuberculosis Eradication Scheme was analysed for copper. Of the 3611 pooled herd samples analysed, approximately 9% had low serum copper concentrations (<7 ¦mol/L). Distribution of those herds identified to be at risk of copper deficiency appeared to be random, apart from areas of high risk on peat soils and the coastal fringe of calcareous sands. Analysis of pasture samples collected from paddocks with cattle having low serum copper concentrations showed that low serum copper was usually associated with raised molybdenum rather than low copper concentrations in pasture. In some instances, moderate concentrations of molybdenum and sulfur in pasture and soil ingestion associated with high iron concentrations may combine to cause hypocupraemia, especially when livestock graze stubbles and subterranean clover pastures in summer-autumn and short pastures in winter. Only 6% of pasture samples had less than 4 mg Cu/kg DM, a concentration which indicates possible copper deficiency in subterranean clover or strawberry clover.