Digestibilité chez la Truite arc-en-ciel (Salmo gairdneri) lors de l'adaptation à un nouveau régime alimentaire

Abstract

We have investigated the experimental conditions necessary to obtain accurate digestibility coefficients in rainbow trout (Salmo gairdneri). These conditions concern the lag period which should be observed after changing the diet, the duration of feces collection, and the number of replicates. Every day we collected automatically and then analyzed the feces of five groups of 15 fish each during the 20 d following the administration of a new diet. As early as the 3rd d after changing the diet, digestibility coefficients took definitive values characteristic of that diet. Thus, there were no adaptation phenomena; we observed only a lag period associated with digestive transit rate. Feces may be collected as soon as on the 3rd d after changing the diet. Finally, "number of replicates × number of days" combinations were established to obtain a given accuracy of digestibility coefficients.