Effects of copper and cobalt supplementation on the growth rate and fertility of Shorthorn heifers in northern coastal Queensland

Abstract

A condition of ill-thrift was studied in weaner cattle in an area south of Townsville consisting of plains of swampy ground interspersed with light sandy ridges. A response was obtained to copper but not to cobalt therapy.
Parenteral copper therapy at 3-monthly intervals resulted in a highly significant growth response in winter and spring. Supplemented heifers showed continued superiority for the duration of the experiment from April 1960 to September 1962. Following mating in March 1961 there was a significantly greater number of pregnancies in copper-treated groups as determined by rectal examination in July 1961. Heifers pregnant at this time had grown more rapidly since the commencement of the experiment, but there was no evidence of delayed onset of oestrus in non-pregnant heifers. Differences between copper and non-copper treated groups in the number of pregnancies decreased at subsequent examinations.
Some initial reduction in fertility was attributable to a high incidence of Vibrio fetus but there were no differences between treatments in the incidence of this disorder.
Liver copper levels were consistently low in untreated animals. Parenteral copper therapy at 3-monthly intervals maintained satisfactory copper reserves except in a period of maximum stress as shown by minimum weight gains from September to December. Calves born to copper-treated cows showed higher initial liver copper reserves. An adequate copper status was maintained in calves treated at 3-monthly intervals.
Analyses of the predominant pasture species showed some seasonal variation in copper content. All findings suggest that copper deficiency in cattle in this locality is due to an interference with copper metabolism in the animal rather than a low copper status in the diet. This interference factor does not appear to be molybdenum in the presence of inorganic sulphate.
Scoring for coat colour and felting established a shorter, smoother coat in copper-treated animals.