Zinc distribution in the small-intestinal digesta of pigs fed skim milk powder or defatted soybean flour.

Zinc distribution in the small-intestinal digesta was studied in pigs fed a skim milk powder (SMP)-based or defatted soybean flour (DSF)-based diet. Ten pigs were fed experimental diets for 30 d. Serum and femoral zinc concentrations were lower in the DSF group than in the SMP group, suggesting the lower zinc availability in the DSF diet than in the SMP diet. In the digesta of small intestine, zinc solubility was higher in the SMP group than in the DSF group. A gel permeation high-performance liquid chromatography showed that the SMP group exhibited four zinc peaks in the chromatogram of the supernatant of digesta. The chromatogram in the DSF group showed four zinc peaks corresponding to those of the SMP group. However, the first zinc peak was smaller and the second peak was larger in the DSF group than in the SMP group. Dietary treatment did not affect the other peaks of zinc. Although the high solubility of zinc in the digesta of SMP group is considered to result in the high availability of zinc, the difference of zinc distribution in the liquid phase of digesta may partly affect zinc availability.