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An investigation of in vitro enzymatic amino acid digestibility of autoclaved rapeseed meals using the enzyme pronase is presented. A correlation coefficient of 0.991 was obtained when comparing in vitro "available" lysine with "Silcock available" lysine. Autoclaving of rapeseed meal for periods of 15, 30, 60, 120 and 180 min at 103 kPa and 120°C caused the following chemical changes. Lysine, methionine and cysteine in vitro digestibilities were markedly decreased as to a lesser extent were the other amino acids. Conversion of methionine to methionine sulphoxide occurred. Deactivation of trypsin inhibitor from 3.8 units of trypsin inhibitor/mg rapeseed for the non-autoclaved meal to zero for the 15 min autoclaved meal was observed. The in vitro enzymatic method described shows considerable promise as a technique to measure amino acid availability.

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