Improvement of fermentation quality and cellulose convertibility of Napier grass silage by inoculation of cellulolytic bacteria from Tibetan yak (Bos grunniens).

AIMS

To isolate and identify cellulolytic bacteria from yak rumen and further evaluate the effects of the isolates on the silage quality, structural carbohydrates degradation and cellulose convertibility of Napier grass silage.

METHODS AND RESULTS

Two out of 218 strains were selected based on their most extensive transparent zone and the highest filter paper disintegration rate. The two isolates (JFL12 and JF85) could grow normally at 15-55°C, pH 3·0-7·0 and NaCl (3·0, 6·5%), and were identified as Enterococcus casseliflavus and Enterococcus faecalis by 16S rDNA sequence analysis, respectively. Napier grass was ensiled with no additive control (C), Lactobacillus plantarum (Lp), JFL12, JF85, JFL12 + Lp and JF85 + Lp for 3, 5, 7, 14, 30 and 60 days. All inoculated silages had higher lactic acid content, lower pH, ammonia nitrogen (NH -N) and lignocellulose contents than the control silage. Silages treated with JFL12 + Lp and JF85 + Lp had the lowest pH and NH -N contents, the highest lactic acid content and lignocellulose degradation among all treatments. The isolates with or without Lp significantly (P < 0·01) increased water soluble carbohydrates (WSC), glucose, fructose and sucrose contents as compared with the control silage. Silages treated with JFL12 + Lp and JF85 + Lp had higher glucose yield and cellulose convertibility than the other silages.

CONCLUSIONS

Therefore, the application of isolates (JFL12 and JF85) with Lp had synergistic effects on accelerating the degradation of structural carbohydrates and improving the silage quality.

SIGNIFICANCE AND IMPACT OF THE STUDY

Napier grass presents difficulty to ensiling due to its low WSC and high structural carbohydrates contents. The screened cellulolytic bacteria could be a candidate strain in improving fermentation quality and structural carbohydrates degradability of ensiled forages.