Bioavailability of two organic forms of zinc in comparison to zinc sulphate for weaning pigs fed a diet composed mainly of wheat, barley and soybean meal

This study was performed to compare the bioavailability of two organic zinc compounds, a zinc glycinate complex and a zinc amino acid chelate with that of zinc sulphate in growing pigs fed a basal diet composed mainly of wheat, barley and soybean meal. The experiment included 96 pigs with an average body weight of 8 kg, allotted to ten groups of nine to ten pigs each. The first group received the basal diet, containing 42 mg of native zinc per kg, without zinc supplementation over a period of five weeks. The other nine groups received the basal diet supplemented with 15, 30 or 50 mg of zinc/kg as zinc sulphate, zinc glycinate or the zinc amino acid chelate. Pigs fed the unsupplemented diet had a lower growth performance (body weight gain, feed conversion ratio) than the other nine groups. Supplementation of 15 mg zinc/kg diet (irrespective of zinc form) was sufficient to yield optimum growth performance. Plasma zinc concentration and activity of alkaline phosphatase were rising with increasing zinc supplementation levels up to a maximum reached at a supplementary level of 30 or 50 mg/kg diet for activity of alkaline phosphatase and plasma zinc concentration, respectively. The response of those parameters to zinc supplementation did, however, not differ between the three zinc compounds considered. The apparent digestibility of zinc from the diet was also not different for the three zinc compounds. In conclusion, these findings show that the bioavailability of the two organic zinc compounds did not differ from that of zinc sulphate in growing pigs fed a diet with wheat, barley and soybean meal as major components.