The chemical composition and nutritive value of rice straw after treatment with urea or Coprinus fimetarius in a solid state fermentation system

Abstract

The process of solid substrate fermentation (SSF) using Coprinus fimetarius 386 on rice straw on a pilot scale was standardized and evaluated by conducting feeding trials on goats, in comparison with urea (ammonia)-treated straw. Three experiments were carried out; in Experiment 1, the fungal-treated rice straw was prepared with 4 weeks SSF and evaluated for its nutritive value, whereas in Experiment 2, the dry matter losses at different periods of SSF were determined with view to reduce the fermentation period, and subsequently the SSF period was reduced from 4 to 2 weeks in Experiment 3. The results indicated that dry matter recovery was progressively reduced as the fermentation period increased in fungal-treated rice straw (FTRS). The chemical composition also revealed lower contents of organic matter, cell walls, ADF and cellulose in FTRS than chemically treated rice straw (CTRS). The dry matter intake was not significantly different in FTRS after 4 weeks fermentation period, but it increased significantly ( P < 0.01) when the fermentation period was reduced from 4 to 2 weeks. The dry matter intake (DMI) per kg metabolic body size was higher ( P < 0.01) in fungally treated straw supplemented with molasses (FTRSM) than chemically treated straw supplemented with molasses (CTRSM) in Experiment 3. The digestibility coefficients of most nutrients in both experiments were not found to vary between the two groups, except cellulose digestibility which was lower in both experiments, whereas hemicellulose digestibility increased ( P < 0.05) in FTRSM as compared to CTRSM group. Both N intake and digested N values were higher ( P < 0.01) in the FTRSM group. The N balance, N retention to total N intake ( P < 0.05) and percent N retention to digested N were higher ( P < 0.01) in FTRSM than the CTRSM group. The DMI and DCP values in both experiments were improved by fungal treatment, whereas improvement in the energy value (TDN) was highly associated with loss of dry matter during fermentation. It is concluded that the nutritional value of rice straw for ruminants may be improved by fungal treatment by appropriate manipulation of fermentation conditions and duration.