Growth prediction of young chicks: do equal deficiencies of different essential amino acids produce equal growth...

1. Prediction of the growth of young chicks was attempted by means of a computerised mathematical model, by fitting a 4 parameter kinetic equation (Mercer, 1982) to data obtained experimentally and from the literature. Amino acid antagonisms between arginine and lysine, and between branched-chain amino acids were taken into account. 2. In order to pool the data, dietary concentrations of essential amino acids were standardised by expressing as percentages of requirements according to Japanese Feeding Standard (1984), and growth responses were expressed relative to growth at or above this requirement. 3. The kinetic model gave an excellent fit (R2 = 0.92-0.99) to independent growth data obtained experimentally and from the literature, validating the use of the equation. 4. It was implied from predicted growth that the responses to alterations in dietary concentrations of different essential amino acids differed substantially, in a characteristic pattern, even when percentages of requirements were the same. 5. The validity of the model was tested against data that were not used in its construction. It was found that the simulation model could predict the growth of young chicks satisfactorily from dietary amino acid patterns.