Alkali treatment and fermentation of straw for animal feed

The feed value of annual ryegrass straw was improved by treatment with various concentrations of NaOH or NH 3 followed by fermentation of the treated straw with a mixed culture of Cellulomonas sp. and Alcaligenes faecalis . Laboratory feeding trials with voles showed that NaOH or NH 3 treatment considerably increased the feed efficiency of straw, but apparently gave a poorly palatable product. Fermentation tended to decrease the in vitro rumen digestibility (IVRD) of alkali‐treated straw. The fermentations were carried out aerobically on a semisolid straw matrix having 11–86% moisture. Treatment by both NaOH and NH 3 increased the IVRD of straw. NH 3 also increased the nitrogen content in straw. The optimum condition for alkaline treatment of the straw was 4–6% NaOH for 1 hr or with 3% NH 3 for four weeks at room temperature. A minimum of 63% moisture was needed for significant fermentation of the straw. The combined effects of NaOH treatment and fermentation more than doubled crude protein, doubled crude fat, and increased IVRD by 75%. The NH 3 plus fermentation treatment tripled crude protein, doubled crude fat, and increased IVRD by 60%. Acetic acid was the main volatile fatty acid in the fermented straw.