Availability to pigs of amino acids in cereal grains. 4. Factors influencing the availability of amino acids and energy in grains

1. Protein digestibility and lysine availability were determined in a range of grain samples using an in vivo digestibility assay calibrated with ileal digestibility values. 2. Mean (+/- SE) values predicted for nitrogen digestibility were 0.92 +/- 0.011 in wheat and 0.88 +/- 0.021 in barely, and the predicted lysine availability in wheat was 0.86 +/- 0.021. 3. Chemical and physical characteristics of the grains were determined and those most closely associated with protein digestibility for wheat were the contents of hemicellulose, neutral-detergent fibre, the bulk density, and to a lesser extent, N and acid-detergent fibre content. These relationships were used to determine prediction equations for the availability lysine content of wheat.