ESTIMATES OF COPPER BIOAVAILABILITY FROM LIVER OF DIFFERENT ANIMAL SPECIES AND FROM FEED INGREDIENTS DERIVED FROM PLANTS AND ANIMALS

Bile Cu accumulation in Cu-depleted chicks fed Cu concentrations between .56 and 1.56 mg/kg was used to estimate Cu bioavailability in several feed ingredients from both plant and animal sources, including liver from different species. Liver from slaughtered animals is rich in minerals and vitamins and is a significant source of Cu in canned pet foods. Liver from different species, however, was found to vary widely in Cu bioavailability (relative to CuSO4.5H2O, which was set at 100%). The bioavailability of Cu in freeze-dried (FD) chicken liver and poultry by-product meal was 116 and 97%, respectively, but that in FD pork liver was not different from zero. Relative bioavailability of Cu in FD beef, sheep, and turkey liver was 82, 113, and 83%, respectively. Copper in FD liver from the rat, a species that does not possess a gall bladder, was 21% bioavailable. Copper in the feed ingredients from plants: com gluten meal, dehulled soybean meal, cottonseed meal, peanut hulls, and soy mill run was 48, 38, 41, 44, and 47% bioavailable, respectively. In addition, when the fibrous ingredients peanut hulls or soy mill run were added to the basal diet containing .5 mg Cu/kg from CuSO4.5H2O, Cu bioavailability in CuSO4.5H2O was reduced. The results of this study demonstrate a wide variation in Cu bioavailability among feed ingredients originating from plants and animals.