Abstract:

[Objective] This study was conducted to assess the effects of different addition levels of compound bacterial inoculants on nutritional value and fermentation quality of Pennisetum purpureum × P. glaucum cv. Reyan No. 4 silage. [Method] Using Pennisetum purpureum × P. glaucum cv. Reyan No. 4 with adjusted water content at around 60% as experiment material, one control （CK group） and four test groups were set up based on single factor experiment design. Each group of Pennisetum purpureum × P. glaucum cv. Reyan No. 4 weighed 90 kg. The CK group did not have any bacteria addition, while the test groups had compound bacterial inoculant additions consisting of different ratios of five silage fermentation bacteria （Lactobacillus + Saccharomyces + Bacillus subtilis + Bacillus licheniformis + Lactobacillus planturum）. The addition levels of the compound bacterial inoculants for the test groups Ⅰ to Ⅳ were 10 g+15 g+10 g+10 g+5 g, 10 g+15 g+15 g+15 g+10 g, 10 g+15 g+20 g+20 g+15 g, and 10 g+15 g+25 g+25 g+20 g, respectively. Each group was repeated three times. After 30 d of silage fermentation, the quality sensory evaluation, nutrient composition analysis, and fermentation quality determination of the silage fermentation products in each group were carried out immediately after opening the bags. [Result] The silage in the test groups Ⅰ and Ⅲ had better quality sensory evaluation with superior grade. There was no significant （P>0.05） difference in dry matter content among the different groups. The crude protein content in the test group Ⅰ was significantly （P<0.05） higher than that in the test groups Ⅱ and Ⅲ. The starch content in the test groups Ⅰ and Ⅱ was significantly （P<0.05） higher than that in the CK group as well as the test groups Ⅲ and Ⅳ. The crude ash content in the test group Ⅲ was the highest, which was significantly （P<0.05） higher than that in the CK group and the other test groups. The four test groups all had significantly （P<0.05） higher water-soluble carbohydrate content than the CK group, and the highest value was observed in the test group Ⅰ. There was no significant （P>0.05） difference in crude fat content among the different groups. The highest total fatty acid content was found in the test group Ⅲ, showing a statistically significant （P<0.05） difference compared with the CK group. The neutral detergent fiber content in the four test groups was all significantly （P<0.05） lower than that in the CK group. The acidic detergent fiber content in the test groups Ⅰ and Ⅱ was significantly （P<0.05） lower than that in the test group Ⅳ, while that in the test groups Ⅲ and Ⅳ was significantly （P<0.05） higher in comparison to the CK group. The lignan content in the test group Ⅱ was significantly （P<0.05） lower than that in the CK group. Among the four test groups, the 30 h neutral detergent fiber digestion rate in the test group Ⅰ was the highest, while that in the test groups Ⅱ, Ⅲ, and Ⅳ was significantly （P<0.05） lower compared with the CK group. No significant （P>0.05） differences in the contents of calcium, phosphorus, magnesium, potassium and sulfur elements as well as chloride ion were found among the different groups. There were no significant （P>0.05） differences in the contents of lactic acid and acetic acid among the different groups. The test group Ⅰ had the highest lactic acid content, while the test group Ⅳ had the highest acetic acid content. The butyric acid content in test groups Ⅰ, Ⅱ, and Ⅲ was significantly （P<0.05） lower than that in the CK group. The ammonia nitrogen content in the test group Ⅲ was significantly （P<0.05） lower than that in the CK group. [Conclusion] The addition of the compound bacterial inoculant consisting of 10 g of Lactobacillus, 15 g of Saccharomyces, 10 g of Bacillus subtilis, 10 g of Bacillus licheniformis, and 5 g of Lactobacillus planturum to 90 kg Pennisetum purpureum × P. glaucum cv. Reyan No. 4 with the adjusted water content around 60% was favourable to improve the nutritional value and fermentation quality of the silage.

Key words: Pennisetum purpureum × P. glaucum cv. Reyan No. 4, silage, nutritional value, fermentation quality, compound bacteria