Effects of zinc source and phytate on zinc absorption by in situ ligated intestinal loops of broilers

Two experiments were conducted to investigate the effects of Zn source and phytate on Zn absorption in broilers. In experiment 1, eight different Zn sources, including ZnSO4, Zn Gly chelate, Zn Met chelate, and Zn amino acid C complex with the weak complex strength (Zn AA C), Zn protein B complex with the moderate complex strength (Zn Pro B), and zinc protein A complex with the strong complex strength (Zn Pro A), and the mixtures of ZnSO4 with either Gly or Met (Zn + Gly or Zn + Met, respectively) were used to study the effects of Zn sources on Zn absorption by in situ ligated intestinal loops of broilers. In experiment 2, 3 x 4 factorial arrangements of treatments involving 3 phytate levels and 4 Zn sources were used to investigate the effect of phytate on Zn absorption. Three molar ratios of phytate to Zn were 0, 2: 1, and 10: 1, respectively, and 4 Zn sources included ZnSO4, Zn AA C, Zn Pro B, and Zn Pro A, respectively. No differences (P > 0.05) were found among the absorption percentages of Zn as Zn + Gly, Zn + Met, and ZnSO4 in 3 intestinal segments. The absorption percentages of Zn as Zn Gly chelate, Zn Met chelate, Zn AA C, Zn Pro B, and Zn Pro A in the duodenum and jejunum were 29 to 129% higher (P < 0.05) than those of Zn as ZnSO4, Zn + Gly, and Zn + Met in the following order: Zn Pro A > Zn Pro B > Zn AA C > Zn Gly chelate or Zn Met chelate > ZnSO4, Zn + Met, or Zn + Gly. The changes of Zn absorption as different Zn sources in the ileum were also observed and were similar to those in the duodenum and jejunum. There was a significant interaction (P < 0.05) between phytate levels and Zn sources on Zn absorption in 3 intestinal segments. The absorption percentage of Zn as ZnSO4 in the duodenum with a phytate-added group (10: 1) was 40% (P < 0.05) lower than that of Zn as ZnSO4 without a phytate-added group. With the increasing phytate levels, the changes of Zn absorption as organic Zn sources in 3 intestinal segments were similar to those of ZnSO4 in the duodenum. However, the reduction of Zn absorption as organic Zn sources was lessened with the increasing complex strengths, and the highest absorption of Zn as Zn Pro A was observed. These results indicated that the absorption of Zn as organic Zn was more effective than that of Zn as inorganic Zn. The organic Zn absorption increased with the increasing complex strengths as well. The simple mixture of ZnSO4 with amino acid did not increase Zn absorption. In addition, the phytate could reduce Zn absorption as different Zn sources in 3 intestinal segments. Organic Zn sources could lessen the negative effect of phytate on Zn absorption, and then the absorption of organic Zn, especially Zn Pro A with strong complex strength, was more effective than inorganic Zn under the high levels of phytate.