[en] The effects of 100 KGy of gamma irradiation on dry matter and organic matter digestibility determined in vitro to improve the nutritive value of three types of blocks containing different feed stuffs were investigated. The compositions of the blocks were type I (wheat bran 28%, dried poultry manure 31%, molasses 20%, urea 10%, Ca(OH)2 6%, salt 5%). Type II (wheat bran 22%, dried poultry manure 10%, sugarbeet 30%, molasses 20%, urea 8%, Ca(OH)2 6%, salt 4%). Type III (olive-oil cake 35%. Wheat bran 30%, urea 100%, cement 15%, salt 10%). The results indicate that there was a significant difference (0.05) between the treated samples and the control for NDF, dry matter and organic matter digestibility. Gamma irradiation resulted in a significant increase (P<0.05) in dry matter and organic matter digestibility and a significant decrease (P<0.05) in NDF contents for the three types of feed blocks. Dry matter digestibility increased by 5% for all block types whereas organic matter digestibility increased by 7%, and 10% for block types I, II and III respectively. The increase in organic matter digestibility was probably due to a decrease in NDF content resulting from gamma irradiation. NDF decreased by 25%, 19% and 16% for block types I, II and III respectively. (author). 23 refs., 4 figs., 2 tabs