The surgical castration of male piglets without anaesthesia is criticised for animal welfare reason. One possible solution seems to be the fattening of boars instead of castrated males. Boars showed a superior growth performance, a reduced feed consumption as well as a higher lean meat content in the carcass. That is why an undefined higher requirement of essential amino acids in the diets for boars was assumed in order to exploit their genetically determined growth potential. Therefore, in the present study the effect of a varying dietary amino acids and partly energy levels on voluntary feed intake, growth performance, nitrogen retention and on chemical body composition of growing-finishing boars of different sire lines was examined. The results of the study pointed out, that clearly increased dietary amino acid contents will not lead to improved performance of boars. It was determined that the AA and energy requirements of growing-finishing boars were not as high as expected in some literature and therefore should be based on a transitional basis on the recommendations of the GfE for pigs with very high protein deposition rates.