Antinutritional factors, metabolizable energy and chemical composition of rice bran

M. Y. Abd. Rahman and S. Mahmood

Abstract

Rice bran (RB) samples from the United Kingdom (UK) and Malaysia were analysed for their metabolizable energy (ME), proximate values, mineral contents, amino acid profiles and activities of antinutritional factors, namely lectin (haemagglutinin) and trypsin inhibitor (TI). The lectin activity in the fullfat RB had its greatest haemagglutinating effect on human type B erythrocytes. Defatted RB had no agglutination in any of the blood types tested. In the UK, autoclaving of RB for 5–20 min at 15 psi (121 °C) reduced the lectin and TI activities to 12–25% and 7–10% of its original values respectively, as compared with the activity in the raw forms. However, in Malaysia, autoclaving of RB sampels for 20 min totally destroyed the activity of TI and suppressed their lectin activity to about one half of its original activity. The mean proximate values of the Malaysian RB were: 13.6% crude protein, 9.3% crude fibre, 14.3% ether extract, 7.6% ash and 10.1 MJ/kg of calculated ME. However, when tested on adult cockerels, the ME values ranged from 12.5 to 14.0 MJ/kg. The Malaysian RB contained 0.06% calcium, 0.64% magnesium, 1.50% phosphorus and 1.21% potassium. It also contained 155 ppm manganese, 128 ppm iron, 8 ppm copper and 123 ppm zinc. Lysine content of the RB collected in Malaysia was low and was not well balanced for poultry diet.

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