Factors affecting trace element status in calves in NW Spain

The aim of the present study was to determine how trace metal concentrations in beef-cattle in NW Spain vary between farms (including farms that have intensive, conventional and organic management practices) and to determine what the likely major causes of such variation are. Soil, feed (forage and concentrate) and animal tissue (liver and kidney; n = 165) samples were collected from three neighbouring farms in each of three districts in Galicia (9 farms in total). Trace metal concentrations (Co, Cr, Cu, Fe, Mn, Mo, Ni, Se and Zn) of digested samples were determined by ICP-MS/OES. Farm husbandry practices that involved use of a high proportion of in-farm produced forage and low/no mineral supplementation, as typically practiced by organic farms, were associated with mineral deficiencies or physiological imbalances in calves. Strict management of the feed ration is needed to avoid sub-clinical or marginal deficiencies which are difficult to diagnose clinically but can cause physiological stress and decreased production. The widely practiced mineral supplementation of concentrates on intensive and conventional systems guarantees that the physiological trace element requirements of calves are met, even when concentrates comprise a relatively low proportion of the diet. However, because of the particular susceptibility of ruminants to chronic copper toxicity, particular care must be taken when concentrates are supplemented above physiological requirements