Study On Relative Bioavailability Of Zinc Methionine Chelate And Regulation Of Phosphorus Absorption In The Small Intestine Of Broilers

Two studies were conducted to evaluate the relative bioavailability of organic Zn-methionine chelate relative to inorganic Zn source(Zn SO4·7H2O) for broiler chicks fed a conventional corn-soybean meal diet, and the regulation factors and potential mechanisms of phosphorus absorption by in situ ligated duodenum loops of broilers.Experiment 1. Relative bioavailability of organic Zn-methionine chelate for broiler chicks fed a conventional corn-soybean meal diet An experiment was carried out to investigate the bioavailability of the organic Zn-methionine chelate with weak chelation strength relative to inorganic Zn source(Zn SO4·7H2O) for broiler chicks fed a conventional corn-soybean meal diet. A total of 504 1-d-old Arbor Acres commercial male broiler chicks were assigned randomly to one of seven treatments involving a 2 × 3 + 1 factorial arrangement in a complete design with three levels of added Zn(30, 60, or 90 mg of Zn/kg) and two Zn sources(Zn-methionine chelate with weak chelation strength and Zn sulfate) plus a Zn-unsupplemented control diet containing 29.2 mg of Zn/kg by analysis for an experimental phase of 21 days. The results showed that Zn-methionine chelate was more effective than Zn sulfate in improving the average daily gain(ADG) of broilers during d 8-14. Zn concentrations in the bone and pancreas, and pancreas MT m RNA level linearly(P < 0.0001) at 7, or 21 d of age as added Zn level increased. The pancreas MT m RNA level at 7 d and pancreas Zn concentration at 21 d were based on slope ratios from multiple linear regressions on added Zn level, the bioavailability values of the Zn-methionine chelate relative to Zn SO4·7H2O(100%) were 120 and 115%, respectively(P > 0.22). The results indicated that Zn-methionine chelate tended to be more available to broilers than Zn sulfate in enhancing MT m RNA level and Zn concentration in pancreas.Experiment 2. The regulation factors and potential mechanisms of phosphorus absorption by in situ ligated duodenal loops of broilersFour experiments were carried out to study the effects of sodion(Na+), 1,25- dihydroxyvitamin D3(1,25-(OH)2D3), parathyroid hormone fragment(b PTH(1-34)) and p H-values on absorption percentage and rate of inorganic phosphrous(P), and m RNA and protein levels of Type IIb sodium-phosphrous cotransporter(Na P-IIb) in duodenal mucosa of broilers in a completely randomized design, respectively. Ligated duodenal loops were perfused with basal perfusion(p H=6) containing 0, 50, or 150 mmol /L Na+ as Na Cl in experiment 1, containing 0, 30, or 300 pmol/L 1,25-(OH)2D3 in experiment 2, containing 0, 60, or 600 pmol/L b PTH(1-34) in experiment 3, and with the p H 6, or 7 in experiment 4, respectively. Consideration of the need for some Na+ in the P uptake, the perfusates contained 150 mmol/L Na+ as Na Cl except experiment 1. A total of 110 22-d-old Arbor Acres commercial male broiler chicks were randomly allotted to 1 of 9 treatments(each treatment was repeated 10 times using 10 birds, each ligated duodenal loop was considered as a replicate). The perfusates and duodenal mucosa were collected at 40 min after perfusion. The results indicated that compare with the control basal perfusates, basal perfusion(p H=6) containing 50 or 150 mmol /L Na+, 30 or 300 pmol/L 1,25-(OH)2D3, 60 or 600 pmol/L b PTH(1-34) could significantly(P < 0.004) increase the percentage and rate of P absorption in the ligated duodenal loops and improve(P < 0.08) Na P-IIb m RNA level in duodenal mucosa, respectively; However, they had no effect(P > 0.16) on Na P-IIb protein level in duodenal mucosa. And there was no difference(P > 0.9) in the percentage and rate of P absorption between the basal perfusion with the p H values of 6 and 7.In conclusion, the organic Zn-methionine chelate tended to be more bioavailable to broiler chicks than inorganic Zn sulfate in enhancing Zn concentration and MT m RNA level in pancreas; and also the Zn-methionine chelate was more effective than Zn sulfate in improving the growth rate of broilers during d 8-14. Basal perfusion(p H=6) containing 50 or 150 mmol /L Na+, 30 or 300 pmol/L 1,25-(OH)2D3, 60 or 600 pmol/L b PTH(1-34) could significant stimulate the percentage and rate of P absorption in the ligated duodenal loops and improve Na P-IIb m RNA level in the duodenal mucosa.