Bioavailability of zinc from different sources in pigs.

In contrast to inorganic Zn, organic Zn sources are absorbed via peptide or AA transport systems resulting in a higher digestibility and availability. Bioavailability of organically bound Zn seems also to be influenced by the type of complex being used. Forty-two gilts (Large white × Landrace) with initial BW of 24 ± 1.4 kg were allotted to 6 treatments of 7 pigs each. Pigs were fed diets based on corn (Zea mays), barley (Hordeum vulgare), and soybean (Glycine max) meal containing either low or high Zn supplementation with ZnO, Zn-Met 1:2 complex, Zn-Gly, Zn proteinate (Zn-Prot), or Zn-yeast. Diets were fed during a 10-d adaptation followed by a 4-d quantitative collection. Daily feed allowance was restricted to 1400 g/pig. Pigs were weighed at the start and end of adaptation and collection and feed consumption was monitored daily. Dietary Zn addition was 10 and 100 mg/kg feed for ZnO and 10 mg/kg feed for other Zn sources. Corresponding ADG ranged from 437 to 587 g with the lowest (P < 0.05) ADG for 10 ppm ZnO. Only Zn-Met addition increased (P < 0.02) Zn digestibility and retention (P < 0.05). Organically bound Zn, in particular Zn from Zn-Met 1:2 and Zn-yeast, can replace higher dosages of ZnO due to better bioavailability indicating that type of chelate is important for Zn retention. Organically bound Zn may reduce Zn excretion, which consequently may lower the environmental impact.