Sodium hydroxide treatment of rice straw to improve its nutritive value for ruminants
AbstractTwo experiments were carried out to determine the effect of NaOH treatment of rice straw and subsequent neutralization with HCl on its digestibility and intake by sheep. In experiment 1, milled straw was treated with 2·0, 4·0, 6·0, 8·0 or 10·0g NaOH in 60, 120 or 200ml water per 100g straw. After 24 h treated straw was neutralized with HCl and the material subjected to in vitro digestion. Digestibility increased with increasing amount of NaOH and volume of solution. The optimum level of treatment appeared to be between 4 and 8 g NaOH in 120ml water per 100g straw. In experiment 2, chopped straw was mixed with 4·0 or 8·0g NaOH in 120ml water per 100g straw. Treated straw neutralized with HCl after 24 h and dried, or dried directly without neutralization was fed ad libitum to mature sheep together with 100g of urea supplemented concentrate per animal per day. Organic matter digestibility of straw significantly increased by 17 to 20 percentage units when treated with 4·0g NaOH per 100g straw. Doubling the alkali content did not bring about a proportionate increase in digestibility. Neutralization had no significant effect on digestibility and voluntary intake of treated material. Alkali treatment increased dry matter intake by 44 per cent as compared to untreated straw. It is concluded that paddy straw can be upgraded in feeding value to be equivalent to a medium quality hay. The practical application of the method on a large scale will depend upon the development of suitable low cost machinery for mixing alkali solution with straw.