Overfeeding copper during rearing affects the liver function and fertility of replacement dairy heifers.

Abstract

Oversupply of dietary copper (Cu) is common among UK dairy herds, but studies on the long-term outcomes of this oversupply are scarce. A longitudinal study was undertaken to determine the long-term implications when 80 Holstein‒Friesian heifers with a mean (±standard error) age of 4.1 ± 0.1 months and a mean liveweight of 137 ± 2.4kg were fed a recommended (R; 16mg/kg dry matter [DM]) or high (H; 32mg/kg DM) dietary Cu concentration until 6 weeks prior to calving. Hepatic Cu concentrations in bothtreatment groups were elevated into the ranges used to diagnose chronic Cu toxicity in cattle at 6.9 months of age (798 ± 46.4 mg/kg DM for H vs. 643 ± 35.4mg/kg DM for R), with associated evidence of liver damage. Hepatic Cu concentrations then returned to normality but remained higher (p < 0.001) for heifers fed H than for those fed R and were associated with a reduced (p = 0.044) conception rate to first and second services (73.7 ±8.05% for H vs. 91.2 ± 7.68% for R). This retrospective analysis identified pre-study liver damage, which may have affected results. Supplying Cu in excess of requirements resulted in liver damage and reduced conception rates.