[The age as a factor on the nutritive utilization of protein by rainbow trout (author's transl)]

Nutritive utilization of protein was studied in three age weight rainbow trout (Salmo gairdnerii) groups fed on a 37.5% casein-protein diet. As to digestive efficiency age was found to have no influence on the apparent and true digestibility coefficient for protein. On the other hand Biological Value, Net Protein Utilization and Protein Productive Value decreased with age-weight increases, the results being significantly correlated (P less than 0.001) between these parameters and the age-weight of the animals. Relative intake, weight increment and Protein Efficiency Ratio also decreased with age-weight increases.