In individual, single-phase feeding animals were fed extensively (group E--7 animals) or intensively (group I--7 animals) in semi ad libitum system. The mixtures differed in composition as well as energy and nutritional value, with constant ratio of protein to energy of 13.12:1 in intensive feeding and 13.04:1 in extensive feeding. Fibre content per 1 kg mixture was 3.43% in group I and 12.3% in group E. For microbiological studies samples were taken from the duodenum, ileum, jejunum and large intestine and both quantitative and qualitative differences in the microflora of the differently fed groups was found.