Effects of different additives on fermentation quality and microbial population of steam-exploded corn straw

In order to study the effects of different additives on the quality of fermentation and microorganism population of corn straw after steam explosion, dry yellow corn straw was used as the raw material. After steam explosion treatment, Sila-Max, Sila-Mix, and fiber-active bacteria were added for sealing, without any additives as a control. After 60 days of fermentation, samples were taken to analyze the nutritional components, fermentation quality, and microorganism population. The results showed that: 1) Crude protein (CP), neutral detergent fiber digestibility (NDF), acid detergent fiber (ADF) digestibility and crude ash contents of steam-exploded corn stalks under different additive treatments had no significant differences (P > 0.05), but compared with dry-yellow corn straw before steam explosion, CP content steam-exploded corn straw silage increased by 2.01 ~ 2.05 times, while NDF and ADF contents decreased by 18.16% ~ 20.17% and 2.38% ~ 3.94%, respectively. Starch content in the active bacteria group was the highest, and there was no significant difference with Sila-Max and Sila-Mix groups (P > 0.05). 2) During fermentation process, mildewing occurred in the active bacteria group and the CK group, with mold variable of 5.07% and 7.75% respectively, while no mildew appeared in the other treatment groups; 3) The content of lactic acid in the active bacteria group was significantly higher than other treatments (P < 0.05); the content of acetic acid、propionic acid and butyric acid in steam-exploded corn straw in the Sila-Max group was significantly higher than those in other treatments (P < 0.05); 4) Under different additive treatments, the number of microorganisms in steam-exploded corn straw after fermentation showed different changes. The number of lactic acid bacteria in the Sila-Max group was significantly higher than that in other treatment groups (P < 0.05), but no significant difference from the Sila-Max group (P > 0.05); mold was not detected in the Sila-Max and Sila-Mix groups, reaching 3.17 lg cfu·g⁻¹, 3.47 lg cfu·g⁻¹ in the CK group and the active bacteria group; 5) Comprehensive analysis of principal components and membership functions showed that Sila-Max (0.55) > Sila-Mix (0.42) > active bacteria (0.41) > CK (0.20). In summary, different additive fermentation treatments had a certain impact on the fermentation quality and microorganisms population of steam-exploded corn stalks. Although active bacteria increased the content of lactic acid, did not inhibit harmful microorganisms and prevent mildew; Sila-Max increased the content of lactic acid bacteria, acetic acid and propionic acid, inhibited the activities of harmful microorganisms, prevented mildew and have the potential to inhibit secondary fermentation; Sila-Mix increased the content of lactic acid bacteria in steam exploded corn straw, inhibited the activities of harmful microorganisms and prevented mildew. Scores of comprehensive principal components and subordinate functions, the addition of Sila-Max during steam-exploded corn stalks had the best comprehensive performance and could be promoted in practice.