Studies of the effects of energy, protein and mineral supplementation to cattle grazing naturalised pastures on the North Coast of New South Wales

A series of experiments were conducted to measure the response by cattle grazing ʹnative pasturesʹ on the North Coast of New South Wales to supplements of energy, protein and the administration of mineral supplements. In all experiments there were liveweight responses to both energy and protein supplements. The magnitude of the response to the grain supplements was affected by treatment of the grain with extruded grain tending to give a superior liveweight response. The response to nitrogen supplements differed between non-protein-nitrogen (urea) and protein - always in favour of the protein supplement. There were no liveweight responses to copper cobalt or selenium. Supplemental copper administered in a variety of ways increased liver copper concentration, plasma copper and ceruloplasmin and coat colour changed from yellow to red. The low copper storage levels were not associated with high molybdenum values in the feed on offer. Administration of selenium did not increase the unsatisfactory pregnancy rate but did raise the level of circulating glutathione peroxidase.