Effect of feeding urea and acetic acid treated wheat straw on the digestibility of nutrients in adult male murrah buffaloes (Bubalus bubalis)

Wheat straw was treated on laboratory scale with 4% urea at a moisture level of 50% along with different amounts of acetic acid (AA) to fix various levels of ammonia nitrogen (15, 30, 45 and 60%) evolved from urea and stored for 4 weeks. Chemical composition of the treated samples revealed a significant (p <0.01) increase in N content of the samples where AA was added. The N content of the ammoniated straw was only 1.21% which increased to 2.58 with the addition of AA to trap 30% NH3-N. The concentration of free NH3-N in the straw was significantly (p <0.01) less when more than 15% NH3-N was trapped with AA. There was significant increase (p <0.01) in N disappearance and depression in NDF and hernicellulose disappearance, when AA was used to trap 30% NH3-N. Large scale treatment of wheat straw with 4% urea at a moisture level of 50% along with AA (to trap 30% NH3-N) increased the N content, but not as much as in laboratory scale treatment. In vivo experiment conducted on nine adult male buffaloes divided into three groups revealed no difference in the intake of DM, OM, NDF, ADF, cellulose and hemicellulose among group I (ammoniated straw), group II (AA treated ammoniated straw) and group III (AA treated ammoniated straw +1 kg barley grain), but the intake was significantly (p <0.05) more in groups where AA treated straw was fed as compared to only ammoniated straw fed group. However EE digestibility was depressed in group II. The digestibility of cellulose and hemicellulose both depressed significantly (p <0.05) in group II and III as compared to group I. Animals in all the 3 groups showed positive nitrogen balance and it was significantly more in group II and III as compared to group I. DCP intake was significantly (p <0.05) more in group II and III as compared to group I, but there was no significant difference among the three groups in TDN intake. It can be concluded that AA (to trap 30% NH3-N) is effective in capturing the excess ammonia released during urea ammoniation of straw and improving its nutritive value, as well as animal performance.