The effect of protein source in the diet of Zn65 absorption and excretion by chickens. Poultry Science 45

Available evidence indicates that the phytic acid present in isolated soybean pro-tein may make the dietary zinc less avail-able to chickens and swine (O'Dell and Savage, 1960; and Overleas et al., 1962). Zeigler et al. (1961) found that the zinc requirement of chicks fed a casein diet was 12—14 mg./kg- of diet, while the require-ment of chicks fed an isolated soybean pro-tein diet was 27-29 mg./kg. of diet. More recently Savage et al. (1964) pre-sented evidence that fecal zinc excertion was increased by adding phytic acid to a ca-sein-gelatin type diet. The feeding of a soy-bean protein diet caused an increase in the appearance of fecal zinc, as compared to the chicks fed the casein gelatin diet, and while the difference was not significant, the authors state "However, the data strongly suggest that more rapid zinc depletion oc-curs among chicks fed soy protein because of imparied zinc absorption in the presence of this protein." The present experiment was conducted to determine if the effect of isolated soy-bean protein was on the absorption of zinc and to gain further insight as to the size of this effect. EXPERIMENTAL Four teen W h i t e P l y m o u t h Rock cocker-els, approximate ly twenty-eight days of age and weighing an average of 675 grams, were used in this exper iment. Pr ior to being 'This investigation was supported in part by a grant from the Atomic Energy Commission and a research career program award no. 18,411 fro