Liver copper kinetics in Thoroughbred foals at pasture from birth to 160 days of age

Pregnant mares in New Zealand are often kept at pasture with inadequate copper (Cu) concentrations according to National Research Council (1989) recommendations. Many authors recommend Cu supplementation of pregnant mares to reduce the degree and severity of developmental orthopaedic disease (DOD) in their foals. Few data exist on the efficacy of Cu injections in mares in raising liver Cu concentration in pregnant mares or their foals, or the pattern of normal decline in liver Cu concentration of foals after birth. In this study pregnant mares were treated with injectable Cu, or saline, in two different regimens, in 2 consecutive years. Mares and foals had liver biopsies harvested to determine the effect of mare Cu supplementation on liver Cu concentration, and to identify normal patterns of decline in foal liver Cu concentration from birth to 160 days of age. Injectable Cu supplementation had no significant effect on dam or foal liver and plasma Cu concentration. A mathematical model to describe the decline in liver Cu concentration of foals was constructed. In foals the concentration of Cu in liver biopsies showed high repeatability (87%), and was strongly correlated with total liver Cu concentration. Cu injections do not improve Cu status in mares and foals, and liver biopsies are highly repeatable and highly correlated with total liver Cu, thus are a useful tool to evaluate liver Cu stores.