Enriched nutrients of Napier grass using Aspergillus sp. through solid state fermentation

Napier grass (Pennisetum purpureum) is one of the popular tropical grasses. It is widely used to feed ruminant animals. However, the nutrient composition in Napier grass is still low and it is required to enhance the nutritive value of Napier grass using additives (e.g., molasses and fungi) that can fulfill the nutrient requirement by ruminants. Therefore, the objectives of this study were to evaluate the effects of Aspergillus niger and Aspergillus awamori on fermentation characteristics and nutritive values of Napier grass silage through solid-state fermentation. There were 3 treatments with 3 replications for each: i) Control (T1): Napier grass ensiled with 5% molasses, ii) T2: Napier grass ensiled with 5% molasses and Aspergillus niger (10 ml/kg silage; 106 spores/ml) and iii) T3: Napier grass ensiled with 5% molasses and Aspergillus awamori (10 ml/kg silage; 106 spores/ml). Napier grass was harvested at approximate 2 months of plant maturity, chopped manually at 2-3 cm in length, kept it air tight in plastic bag, and then stored it anaerobically for 21 days. The pH value, lactic acid, NH3–N, dry matter (DM), crude protein (CP), ether extract (EE), crude fibre (CF), ash and nitrogen free extract (NFE) contents of silages were evaluated. There were significant (p<0.05) differences on pH value among the treatments. The pH value ranged from 4.08 to 4.20. The T1 silage showed lower (p<0.05) pH value (4.08) than T2 silage (4.20). No significant (p>0.05) differences were observed on lactic acid content in Napier grass silages among the treatments. The NH3–N content in Napier grass silages were significantly (p<0.05) differed among the treatments. The DM, CP, EE, CF and NFE contents in Napier grass silages were significantly (p<0.05) varied among the treatments, while ash contents were not significantly (p>0.05) varied. The T2 silage showed the highest DM (24.04%), CP (11.42%), CF (29.00%) and ash (9.39%) contents, while T1 silage showed the lowest DM (21.04%), CP (9.16%), CF (23.29%) and ash (6.34%) contents. The T2 silage showed the highest EE content (7.65%), while T3 showed the lowest (0.58%). The T1 silage showed the highest NFE content (59.70%), while T2 silage showed the lowest (42.56%). The results of this current study suggest that the ensiled Napier grass with three weeks fermentation period contains the highest levels of CP. Hence, biological treatment of Napier grass using Aspergillus niger enhanced its nutritive value, which might be used for ruminant feed.