Influence of age, sex and cross on body concentrations of trace elements (zinc, iron, copper and manganese) in chickens.

1. Environmental problems in areas of intensive animal production necessitate new constraints in food formulation concerning nitrogen and phosphorus and also concerning trace minerals, especially zinc and copper, which are found in excess in poultry manure in relation to nitrogen and might cause phytotoxicity in soil. 2. Whole body concentrations of zinc, iron, manganese and copper were measured in chickens in order to estimate the percentage of deposition and excretion. Body concentrations were determined on 390 chicks of both sexes at different ages in 2 commercial crosses. 3. Age affected the trace element body concentration. Higher concentrations were observed at earlier ages (4 to 11 d). Sex and cross had little influence on body Zn, Fe, Cu and Mn concentration and interactions were observed between these factors. 4. Body retention percentage (% of intake) was very low when birds were fed on commercial diets and decreased with age. For the period 0 to 40 d, the percentages of retention were 6%, 10%, 0.2% and 6% for Zn, Fe, Mn and Cu, respectively, and therefore 90% to 99% was excreted. 5. These findings make it possible to calculate trace mineral excretion for various feeding systems and confirm the excess of zinc and copper in poultry manure in relation to nitrogen. A nutritional approach such as reduction in dietary trace mineral supplementation may alleviate the risks of phytotoxicity in the soil resulting from Zn and Cu excesses.