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 betwe en .56 and 1.56 mg/kg was used to estimate Cu bioavailability in sever al feed ingredients from both plant and animal sources, including live r from different species. Liver from slaughtered animals is rich in mi nerals and vitamins and is a significant source of Cu in canned pet fo ods. Liver from different species, however, was found to vary widely i n Cu bioavailability (relative to CuSO4.5H2O, which was set at 100%). The bioavailability of Cu in freeze-dried (FD) chicken liver and poult ry by-product meal was 116 and 97%, respectively, but that in FD pork liver was not different from zero. Relative bioavailability of Cu in F D beef, sheep, and turkey liver was 82, 113, and 83%, respectively. Co pper in FD liver from the rat, a species that does not possess a gall bladder, was 21% bioavailable. Copper in the feed ingredients from pla nts: com gluten meal, dehulled soybean meal, cottonseed meal, peanut h ulls, and soy mill run was 48, 38, 41, 44, and 47% bioavailable, respe ctively. In addition, when the fibrous ingredients peanut hulls or soy mill run were added to the basal diet containing .5 mg Cu/kg from CuS O4.5H2O, Cu bioavailability in CuSO4.5H2O was reduced. The results of this study demonstrate a wide variation in Cu bioavailability among fe ed ingredients originating from plants and animals.