Chemical treatment of rice straw in Malaysia I. The effect on digestibility of treatment with high levels of sodium and calcium hydroxide

C.Devendra

Abstract

The digestibility by sheep of nutrients in diets containing 30, 40 and 50 per cent rice straw treated with 6 and 8 per cent NaOH or Ca(OH)₂ in molasses-based diet is described. The content of crude fibre of untreated rice straw in the dry matter was 30.4 per cent. With 6 and 8 per cent NaOH, the value was improved to 29.0 and 28.2 per cent, and with Ca(oH)_2, 28.8 and 28.5 per cent. Treatment with alkali increased the intake and improved the digestibility of all nutrients significantly (p<0.05). However, the best results were found for the 30 per cent level of rice straw inclusion treated with 8 per cent NaOH. For this treatment, individual digestibilities were improved from 60.3 to 76.0 per cent for dry matter, crude protein from 35.8 to 78.1 per cent, crude fibre from 23.8 to 67.8 per cent, ash from 34.4 to 62.5 per cent and energy from 34.4 to 62.5 per cent. With Ca(OH)₂. the improvements in digestibility were from 66.5 to 73.3 per cent for dry matter, 59.4 to 68.4 for crude protein, 36.4 to 54.4 per cent for crude fibre, and energy from 63.4 to 74.8 per cent. It was calculated that for the 30 per cent rice straw + 8 per cent NaOH diet or Ca(OH)₂ diets, there was an increased intake of 1.3 to 1.4 MJ of ME per sheep per day, equivalent to an increase of 25.2 and 26.2 per cent. A comparison of the effects of both alkalis indicated that NaOH was considerably more superior. The ultimate value of NaOH treatment will depend on type of level used method of application, beneficial responses in feeding trials and cost-benefit analysis.

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