Effect of dietary copper on litter microbial population and broiler performance.

Proprietary broiler diets, containing added copper (125 mg/kg) as sulphate, were fed to broilers in 4 trials (32 pens each) over a one year period without a change of litter. Mould counts in the litter of pens containing birds fed the standard diets decreased to 2 X 10(3) propagules per g in trial 4. Those in the pens with birds fed the diets containing supplemental copper decreased to 6 X 10(2) propagules per g. Litter bacterial counts (10(7) organisms/g) were not affected by dietary copper. Litter copper concentrations in pens where the birds were fed supplemented diets increased significantly to more than 600 mg/kg in trial 4. Dietary copper sulphate addition significantly increased broiler weight gains at 7 weeks in trials 3 and 4 (P less than 0.05) and the efficiency of food utilisation was significantly improved in trial 4. The copper content of the chicks' livers remained unchanged. It is suggested that broiler performance may be independent of dietary copper content. Litter copper concentrations and litter microbial alterations may be important factors.