Minimum levels of inclusion of copper and zinc proteinate amino acid chelates in growing and finishing pig diets

The influence of increasing dietary concentrations of copper (Cu), together with low or high inclusion levels of zinc (Zn), on performance, faecal mineral concentrations and the mineral status of the body was examined in 216 Large White x Landrace pigs (initial weight 27 kg, final weight 107 kg). The base diets were supplemented with combinations of 0, 10, 30 or 50 mg/kg Cu and 40 or 80 mg/kg Zn in the proteinate amino acid chelate form (organic), according to a factorial arrangement of treatments. A control treatment containing levels of Cu and Zn similar to the high organic treatment in the form of sulfate (inorganic) was also included. Blood and faecal samples were collected on Days 21 and 49 of the experiment and tissue samples immediately after slaughter. Across the entire growing and finishing phases, no significant treatment differences (P>0.05) occurred in pig daily gain or feed intake, although feed conversion ratio was improved (P<0.05) by the inclusion of proteinate amino acid chelate. Copper and Zn concentrations in faeces were in direct proportion to their inclusion level in the diet. Blood and tissue mineral concentrations were within normal physiological ranges in all treatments. Results showed that reducing Cu and Zn in grower-finisher diets from 50 to 0 mg/kg Cu and from 80 to 40 mg/kg Zn reduced faecal Cu and Zn concentrations by 90 and 40%, respectively, without compromising pig growth. However, when Cu was supplemented at 0 mg/kg, storage of Cu in the liver approached marginal levels, suggesting that some added dietary Cu is needed in grower-finisher diets, especially for pigs reared in commercial conditions.