Possible factors affecting the bioavailability of copper and the copper requirements of wild, free-ranging African herbivores: A review

Free-ranging wild herbivores in Africa comprise 78 species of ruminants and several species of monogastric hindgut fermenters, and are classified as grazers, mixed feeders, and browsers. The objective of this review is to provide guidance to wildlife nutrition advisers by outlining key metabolic principles relevant to assessing copper nutrition in herbivores. In domestic species, copper bioavailability is influenced by dietary copper antagonists, copper solubility at absorption sites, and the homeostatic regulation of copper metabolism. Differences in the homeostatic control of copper absorption and metabolism in the liver between ruminants and monogastric species have a major effect on their tolerance to excessive copper exposure. As some elements in the diet are antagonistic to copper solubility in the digestive tract, dietary copper concentration alone has limited diagnostic value for assessing the potential copper nutrition status of a ruminant. Dietary copper is most soluble in acidic environments and factors influencing rumen pH, such as the effect of diet type on rumination and saliva flow, could thus influence copper solubility. In monogastric species, the solubility of dietary copper in the stomach can be high (up to 80% in vitro) because of the acidic environment of the stomach. Consequently, in domestic species, the bioavailability of copper varies from 1% to 10% in mature ruminants, compared with an estimated ≥30% for non-ruminants. This suggests that for wild species with similar body weights and diets, dietary copper requirements per kilogram of feed intake for maintenance should be substantially lower for monogastric species than for ruminants. (Submitted 22 June 2025; Accepted 30 August 2025; Published 12 November 2025)