Published online by Cambridge University Press: 09 March 2007
The aim of the present study was to evaluate the influence of breed and other factors (age, sex and season) on copper (Cu) accumulation by calves reared in a region in north-west Spain where pig slurry is widely used for slurry fertilization, and where cattle typically have hepatic Cu concentrations above the generally accepted safe-adequate levels. In December 2000 and August 2001, paired liver and blood samples were obtained at slaughter from 532 male and female Galician Blond, Holstein-Friesian and Galician Blond×Holstein-Friesian calves, aged between 6 and 10 months, from 434 different farms. Samples were acid-digested and Cu concentrations determined by ICP-OES. Holstein-Friesian calves showed significantly higher mean Cu concentrations both in the liver (80·6 mg/kg fresh weight) and blood (0·891 mg/l) than Galician Blond calves (50·4 mg/kg and 0·748 mg/l respectively) and crosses between the two breeds (61·3 mg/kg and 0·829 mg/l respectively). Holstein-Friesian was the breed with the highest percentage (42%) of calves with hepatic Cu concentrations above safe-adequate levels (25 to 100 mg/kg fresh weight) and Galician Blond the breed with the highest proportion (29%) of hypocupraemia during the winter sampling. Considering all breeds, hepatic Cu levels were higher in males (63·8 mg/kg) than in females (53·5 mg/kg) and significantly increased with age in summer. A significant three-way breed×sex×age interaction was observed for liver Cu but this may be attributable to the small number of animals in some groups, having a confounding effect on the analysis. A significant sex×age×season interaction was also observed which could indicate greater male dominance in summer, so that they consume more forage (and thus more Cu) than females. Calves slaughtered in winter showed significantly lower mean blood Cu concentration (0·703 mg/l) than calves slaughtered in summer (0·940 mg/l).