Abstract: To investigate effects of compound chemical treatment on dry matter(DM) and fiber degradation rate of wheat straw in rumen, urea and calcium hydroxide were added on the basis of straw airdried matter with 2%, 3% and 4% respectively, a total of nine experimental groups, urea and calcium hydroxide added in group1 to group9 in turn were: 2%+2%, 2%+3%, 2%+4%, 3%+2%, 3%+3%, 3%+4%, 4%+2%, 4%+3% and 4%+4%,the control(CK) group was the original wheat straw, DM and fiber degradation rate after 72 hours of different treatments for straw were measured by shortterm artificial rumen technique. The results showed that: group 7, 8 and 9 were significantly higher than CK group and other experimental groups (P<0.01) in DM and acid detergent fiber(ADF) degradation rate after 72 hours, which increased by 90.96 %, 85.24%, 75.03% than CK group in DM degradation rate and 139.38 %, 132.06 %, 130.94 % in ADF degradation rate respectively. There was no significant differences (P>0.05) among group 7,8 and 9. Group 7 and 8 were significantly higher than CK group and other six experimental groups (P<0.01) in neutral detergent fiber (NDF) degradation rate after 72 hours, which was increased by 92.06%, 82.51% respectively, and significantly higher than that of group 9 (P<0.05). Under this experimental condition, the treatment added with 4% urea and 2% calcium hydroxide of wheat straw airdried matter was the most suitable compound chemical treatment．

Key words: wheat straw, urea, calcium hydroxide, neutral detergent fiber, acid detergent fiber, rumen degradation rate