Changes in liver copper concentration of Thoroughbred foals from birth to 160 days of age and the effect of prenatal copper supplementation of their dams

Objectives To monitor the change in liver copper concentration of Thoroughb red feats from birth to 160 days of age and to determine the effects of sup plementation by two injections of copper edetate given to dams in late gest ation on the liver copper concentration of their foals at birth. Procedure Ten mares pregnant to the same stallion were randomised into two groups on the basis of age, liver copper concentration and expected foaling date. The treatment group mares were given 100 mg and 250 mg copper edetat e intramuscularly during the ninth and tenth months of gestation respective ly. Foals had liver biopsies taken weekly in the first month of life, then monthly for four months. Feats were euthanased at 160 days of age; liver sa mples were taken and the copper concentrations were determined. Results Two distinct patterns of age dependant decline in liver copper conc entration were evident. The mean (+/- SD) liver copper concentration of the foals was high at birth (374 +/- 130 mg/kg DM), and for seven it declined to adult values by 160 days of age (21 +/- 6 mg/kg DM). In three feats the decline was at a slower rate than in the other seven and at 160 days of age the mean concentration was 162 +/- 32 mg/kg DM. Repeated measures analysis showed significant differences between each biopsy (P < 0.01) and between 'normal' and 'accumulator' foals (P < 0.002). Copper injections given to ma res in late pregnancy had no effect on the liver copper concentration of fo als at birth. Conclusions The significance of the two patterns of age dependant decline i n liver copper concentration is unknown. Parenteral copper supplementation of the dam in late gestation had no effect on the liver copper concentratio n of the foal at birth.