Factors affecting copper utilization

Chick experiments employing a bile copper (Cu) assay were conducted to exploit many factors, both endogenous and exogenous, affecting Cu utilization. Bile Cu increased linearly in Cu-depleted chicks fed Cu concentrations between.56 and 1.56 mg/kg. The linear response surface was used to estimate Cu bioavailability in several feed ingredients, and to investigate the effects of several factors on Cu utilization.Several chick experiments were conducted to investigate possible explanations for why Cu bioavailability in pork liver is zero. One possible explanation was that pork liver may contain compounds, such as zinc (Zn), that directly or indirectly inhibit Cu utilization. Zinc bioavailability (bone Zn assay) in FD pork liver was not different $(P>.05)$ from that in ZnSO$\sb4,$ and iron (Fe) bioavailability (hemoglobin repletion assay) was approximately 40% of that in FeSO$\sb4.$ It has also been suggested that gender differences may influence Cu bioavailability, but, there were no differences between FD barrow liver and FD gilt liver in Cu, Zn, and Fe bioavailability values as determined in both male and female chicks.The effect of processing of pork liver on Cu bioavailability was examined. Autoclaving, acid-hydrolysis, and protease-digestion increased Cu bioavailability in pork liver to 32, 46, and 63%, respectively, from virtually 0% of the Cu in unprocessed pork liver. Addition of EDTA at 200 mg/kg to the diet containing 1 mg Cu/kg from unprocessed pork liver also resulted in an increased Cu bioavailability, to 23%. When FD pork liver, FD bile (porcine and chicken), fiber-rich ingredients (peanut hull meal and soy mill run), or nutrient supplements (L-cysteine and L-ascorbate) were added to the basal diet containing supplemental Cu from CuSO$\sb4,$ Cu bioavailability in CuSO$\sb4$ was reduced by more than 50%.Several experiments were conducted to evaluate the Cu-amino acid complexes, Cu-lysine (Cu-Lys) and Cu-methionine (Cu-Met). Both complexes had Cu that was as available as that in CuSO$\sb4$ as evaluated by both the liver Cu assay and the bile Cu assay. Relative Met bioavailability of Cu-Met was 100% of the standard, i.e., feed-grade DL-Met, and relative Lys bioavailability of Cu-Lys was found to be not different from that in feed-grade L-Lys$\bullet$HCl.Chick experiments were also conducted to investigate whether Cu-Met and Cu-Lys would differ from a standard Cu source (CuSO$\sb4)$ in their reaction to the inhibitory dietary effects of physiologic doses of L-cysteine (4000 mg/kg diet) or L-ascorbate (1000 mg/kg diet).The effect of microbial phytase and 1,25-dihydroxycholecalciferol (1,25-(OH)$\rm\sb2D\sb3\rbrack$ on Cu bioavailability from soybean meal and cottonseed meal was investigated.A precision-fed cockerel digestibility assay using ground corn cobs was conducted to test a theory that birds fed pharmacologic doses of Cu (250 mg Cu/kg diet) may exhibit a higher hemicellulose digestibility due to increased release of lysosomal enzymes in the bile. Copper-loaded cockerels (n = 4) showed significantly higher true dry-matter digestibility, true hemicellulose digestibility, and true metabolizable energy than the control Cu-unloaded cockerels. The preliminary results presented herein demonstrate that pharmacologic doses of dietary Cu may improve hemicellulose digestibility. (Abstract shortened by UMI.)U of I OnlyETDs are only available to UIUC Users without author permissio