Over a period of four weeks 88 piglets of an average weaning weight of 9.5 kg received rations with 2.1, 3.1 and 5.5% crude fibre in the original substance in the form of wheat bran. Between the 42nd and 49th day of life a digestibility investigation was carried out by means of Cr2O3, and on the 42nd and the 63rd day of life the organic acids in the complete gastro-intestinal tract could be ascertained, the causes of which are to be found in the lack of easily soluble carbohydrates (increased passage rate, bran quota). Due to crude fibre, the apparent digestibility of all nutrients decreased, which resulted in a lower live weight on the 63rd day of life. The effect of a bran diet in the alimentary prophylaxis of coli enterotoxaemia is thus furthermore substantiated.