The purpose of carried out investigations was to explain the effect of different levels and kinds of crude fibre given to store pigs during rearing on the diversification of a particular parts of digestive tracts (DT) in fattened pigs. The investigations were performed on 90 hogs at the age of 28 days, weaned at the average body weight of 7 kg. The pigs were divided into three experimental groups, each of them comprised of 30 heads. The pigs from group I were treated as control (K) and were fed with a standard mixture containing 4% of crude fibre. In mixtures given to animals from both remaining groups the fibre concentration was increased up to 7%. In group II (ST) this level was obtained by application of 10-20% of grass meal, in group III (OP) by addition of 23-36% of wheat bran. On 90th day of life the 5 animals from each experimental group were randomly chosen and slaughtered and from each carcass the whole digestive tract was prepared out and there the measurements of particular parts were done according to the Horszczaruk’s method. Performed investigations result in the statement that the kind of crude fibre can be an useful tool in regulation of gastrointestinal organ development in pigs. Addition of grass meal to the mixtures given to store pigs significantly increased (by two-times) the volume of colon and caeca in comparison to control animals. Obtained results indicates that the application of 36% of wheat bran can negatively affect the DT proportions. The animals from this group were characterized by about 3 meters shorter and by one litre less capacity small intestine in comparison to fed grass meal.

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