ESTIMATES OF ZINC AND IRON BIOAVAILABILITY IN PORK LIVER AND THE EFFECT OF SEX OF PIG ON THE BIOAVAILABILITY OF COPPER IN PORK LIVER FED TO MALE AND FEMALE CHICKS

Four chick experiments were conducted to investigate possible explanations for why Cu bioavailability in pork liver is zero. One possible explanation was that pork liver contains compounds, such as Zn, that directly or indirectly inhibit Cu utilization. It has also been suggested that sex differences may influence Cu bioavailability. The effect of freeze-dried (FD) pork liver from gilts vs barrows was first examined. Neither FD gilt liver nor FD barrow liver provided any bioavailable Cu to chicks. The effect of sex of the chicks used in the assay (i.e., male chicks vs female chicks) was also examined, but there were no sex-dependent differences (P > .10) in the slopes of the standard curve generated by added Cu from CuSO4 or in the responses to added FD pork liver. Based on bone Zn uptake, Zn bioavailability in FD barrow liver and FD gilt liver was not different (P > .04) from that in ZnSO4, but Fe bioavailability (hemoglobin repletion assay) was approximately 40% (P < .05) of that in FeSO4 in both FD gilt liver and FD barrow liver.