Scientific feeding experiments were carried out with 7 male castrated pigs of the genetic origin land race pig X large white with the test animals fed individually and the rations containing approximately the same amounts of protein, amino acids, minerals and vitamins but varied amounts of energy. Energy intake was adjusted to three levels: 100%, 85% and 70% of semi-ad-libitum intake (group 1 = 100%). With regard to protein supply there was a subdivision into 30-60 and 60-100 kg live weight. In addition to this, the digestibility of the feed mixture used and the N-balance were determined in both fattening periods. Having reached 100 kg live weight, the animals were slaughtered and a number of slaughtering parameters was determined. The average daily live weight gain in the three test groups was 749, 664 and 540 g over the whole fattening period. The feed expenditure was 3.7, 3.9 and 4.3 kg mixed feed per kg live weight gain so that, with regard to live weight performance and feed expenditure the group with the highest energy supply showed the best results. The level of energy supply had a remarkable influence on the composition of weight gain; thus the amount of fat in the carcass of the animals of groups 3 was by 1.8 kg and 2.5 kg resp. lower than of the animals in groups 2 and 1.