Taking action to reduce the risk of copper toxicity in cattle.

A PAPER by Kendall and others (2015), which is summarised on p 493 in this issue of Veterinary Record focuses on the copper status of cattle, reveals that copper supplementation is pervasive on farms, and that chronic copper toxicity is an emerging risk for a significant proportion of UK herds. A similar situation exists in New Zealand. Data collected by New Zealand animal health laboratories between 2000 and 2014 show that the median value of copper concentrations in liver samples from cattle (primarily dairy) has increased from 380 to 1204 µmol/kg wet tissue (WT). This is approximately equivalent to 1500 to 4800 µmol/kg dry matter (DM) (Fig 1). The number of cases of copper overload also rose alarmingly. Samples with concentrations greater than 3000 µmol Cu/kg WT (12,000 µmol/kg DM) comprised 0.2 per cent of the total in 2000, but 3 per cent in 2014. These trends are undoubtedly due to supplemental copper sources, as dietary copper intake from pasture alone is unlikely to cause such accumulation in liver tissue (Knowles and Grace 2014). FIG 1: Liver copper concentrations as measured in samples collected from New Zealand cattle between 2000 and 2014. The data were sourced from national animal health laboratories (Robert Sanson, NZ AsureQuality, personal communication). To estimate values in units of µmol/kg dry matter, multiply the tissue concentrations by four Kendall and others (2015) suggest at least four reasons why farmers are overfeeding copper to cattle. We …