Effects of reducing copper and zinc supplementation on the performance and mineral status of fattening pigs

Pig manure with high copper (Cu) and zinc (Zn) concentration is applied to the soil, and these trace minerals can accumulate in the topsoil and decrease its fertility. Thus, adjusting concentrations of Cu and Zn in pig diets below current maximum allowance can prevent this risk. Reduction of dietary concentrations of Cu and Zn reduces their faecal excretion since only a small portion is retained in the pig’s body. The aim of this study was to evaluate the effects of reducing concentration of dietary Cu and Zn or withdrawing their supplementation on the performance and mineral status of fattening pigs. Four dietary treatments were compared: a basal diet (WS; withdraw supplementation), with no Cu or Zn supplementation (5 and 29 mg/kg of native Cu and Zn, respectively); intermediate concentration (O_INT), supplemented with Cu and Zn oxides to obtain mean dietary concentration of 7.4 and 47.5 mg/kg of Cu and Zn, respectively; and two diets supplemented with oxides (O_REG) or sulphates (S_REG) at concentration similar to European Union limits (i.e. 25 and 120 mg/kg of total Cu and Zn, respectively), as commonly used on commercial farms. Ninety-six pigs (24.3 ± 3.3 kg BW) were each assigned to one of the four treatments and reared in individual pens for 14 weeks (up to 110.3 ± 8.9 kg BW). Animal performances were measured, and samples of plasma (on day 1 and day 41 of experimentation and at slaughter), bones and the liver (at slaughter) were collected from all pigs. Faecal samples were collected from all pigs every 3 weeks to determine the Cu and Zn excretion. Over the entire experiment, neither the concentration nor the source of Cu and Zn influenced feed intake, BW or the feed conversion ratio. Plasma Cu and Zn concentrations were not influenced by the treatment but increased as the age of the pigs increased. Liver Cu concentration increased (P < 0.05) as dietary concentrations increased (O_REG> WS). Neither the concentration nor the source of Cu and Zn influenced bone Cu and Zn concentration or physical bone parameters. However, S_REG had a higher maximum load until bone breaking (P < 0.05) than O_REG. As expected, faecal excretion of Cu and Zn decreased (P < 0.01) as dietary concentration decreased. Dietary Cu and Zn can be reduced without decreasing the performance or mineral status of pigs, and these results should be validated on commercial farms that have more challenging health conditions.