An experiment was carried out to study the effects of different doses of y irradiation on the changes in the crude fibre contents of cottonwood, wheat straw, barley straw, lentils straw, maize straw and maize cobs. Ground samples of the 6 residues were irradiated by y irradiation at doses of 0, 10, 50 and 100 kilogray (kGy) under identical conditions of temperature and humidity and analyzed for total nitrogen (N), crude fibre (CF), neutral-detergent fibre (NDF), acid-detergent fibre (ADF) and acid-detergent lignin (ADL). The results indicate that y irradiation has no effect on total N whereas it decreased CF contents especially at the highest dose (100 kGy) reaching 30% for cottonwood, 21% for wheat straw and maize straw, and about 16% for barley straw, lentils straw and maize cobs. NDF decreased by about 6% for cottonwood, wheat straw and barley straw, 11% for maize straw and 9% for maize cobs. v Irradiation (100 kGy) also decreased ADF by 8% for cottonwood, 7% for maize straw and maize cobs, and 6% for wheat straw and barley straw. No effects on NDF and ADF in lentils straw were observed. ADL content was also decreased by 8% in cottonwood, 21% in wheat straw, 18% in barley straw and maize straw, and by 30% in maize cobs, with no effect in lentils straw. The percentage of cellulose (CL): CF ratio increased by 31, 25, 13, 18, 19 and 15% for cottonwood, wheat straw, barley straw, lentils straw, maize straw and maize cobs, respectively. Also hemicellulose (HCL) : CF ratios increased by 48, 18, 15, 17, 5 and 4% for cottonwood, wheat straw, barley straw, lentils straw, maize straw and maize cobs, respectively, and 48%, 18%, 15%, 17%, 5% and 4% in the HCL:CF ratio for cottonwood, wheat straw, barley straw, lentils straw, maize straw and maize cobs, respectively. CL:ADL ratios increased by y irradiation (100 kGy) by 23, 16, 14 and 38% for wheat straw, barley straw, maize straw and maize cobs, respectively, with no changes in the ratios for cottonwood and lentils straw. HCL :ADL ratios also increased in 4 residues reaching: 11, 16, 17 and 25% for cottonwood, wheat straw, barley straw and maize cobs, respectively, with no changes in the ratio for lentils straw and maize straw.