Copper bioavailability in pork liver and in various animal by-products as determined by chick bioassay

Three chick experiments were conducted to investigate possible explanations for why pork liver provides no bioavailable Cu to chicks. Autoclaving, acid-hydrolysis, and protease-digestion increased (P < .01) Cu bioavailability in pork liver to 32, 46, and 63%, respectively, from virtually 0% of the Cu in unprocessed pork liver (relative to CuSO4, which was set at 100%). Addition of EDTA at 200 mg/kg to the diet containing 1 mg of Cu/kg from unprocessed pork liver also resulted in an increased (P < .07) Cu bioavailability, to 23%. Tissues representing different sources of endogenous Cu in the pig also were evaluated for their Cu bioefficacy. Freeze-dried (FD) porcine bile did not have any bioavailable Cu, whereas spray-dried porcine plasma contained Cu that was as available (99%) as that in CuSO4. In addition, when FD pork liver or FD porcine bile was added to the basal diet containing .5 mg of Cu/kg from CuSO4, Cu bioavailability in CuSO4 was reduced (P < .05) to 34% and 19%, respectively, of values obtained with CuSO4 alone. An additional experiment was conducted to estimate Cu bioefficacy in selected animal-source feed ingredients. Copper bioavailability in all-beef meat and bone meal, all-pork meat and bone meal, mixed-species meat and bone meal, high-bone meat and bone meal, poultry byproduct meal, and hog hair meal was 4, 53, 28, 8, 42, and 9%, respectively, relative to CuSO4. Feather meal did not provide any bioavailable Cu to chicks.