Effect of different steam explosion conditions on the feeding value of corn straw

To study the application of steam blasting technology in straw processing, different moisture contents (50%～60%, 60%～70%, and 70%～80%) of corn straw and steam explosion pressures (0.8, 1.0, and 1.25 MPa) of a steam explosion device were applied. The nutritional value, in vitro gas production, and fiber structure were analyzed to study the effect of different steam explosion parameters on the corn straw value. The results showed that the contents of neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) of corn stalks decreased significantly after steam explosion (P < 0.05). The relative feeding value (RFV), dry matter intake (DMI), digestible dry matter (DDM), total digestible nutrient (TDN), and lactation net energy (NE_L) of corn straw after explosion increased significantly (P < 0.05). Under 1.25 MPa pressure and 50%～60% moisture content, the RFV and DMI were 95.65% and 70.64% higher, respectively, than that of the non-explosion corn. DDM, TDN, and NE_L increased by 25.41%, 60.18%, and 44.57% under 1.25 MPa and were 50%～60% compared to those of the untreated samples. The cumulative as production for 48 h at an explosion pressure of 1.0 MPa and straw moisture of 70%～80% was significantly higher than that of the other treatments (P < 0.05) and was the lowest for the non-steam explosion. The steam explosion treatment also significantly increased the in vitro dry matter digestibility (IVDMD) of corn straw (P < 0.05), which showed the same trend as that of the in vitro gas production. The extent of the degree of straw fiber structure degradation increased with the pressure of the steam explosion chamber and the moisture content of the raw straw material, and the straw changed from block or schistose into filiform. Under an explosion pressure of 1.25 MPa and a corn straw moisture of 50%～60% and 60%～70%, the fiber structure of the straw was obviously damaged. Therefore, a pressure of 1.0 MPa with a moisture content of 70%～80% were the optimal parameters for corn straw steam explosion.