A preliminary study toward the improvement of low fishmeal diet utilization in a Yamanashi strain of rainbow trout Oncorhynchus mykiss

Abstract

For future sustainable aquaculture practices, utilization of a low fish meal diet in a Yamanashi strain of rainbow trout was compared with another strain. In addition, efficacy of selective breeding for the low fishmeal diet was preliminarily examined in the Yamanashi strain. A 50% fishmeal diet (FMD) and a soybean and corn gluten meal-based 5% fishmeal diet (LFMD) were fed to apparent satiation to the juveniles of Yamanashi control strain (YC), Shiga Samegai strain (SS) and Yamanashi strain selectively-bred for one generation with LFMD (YS). Growth and feed utilization for the respective diets were similar between YC and SS strains. Among fish fed LFMD, apparent dietary crude protein and fat digestibility coefficients were higher in YC than those in SS. Selectively-bred YS showed superior growth and feed efficiency to YC for the respective diets due largely to increased feed intake. However, limited improvements in the physiological conditions were observed in YS fed LFMD. An additional trial under restricted feeding of LFMD revealed that growth and feed efficiency ratio of YS were superior to YC. These results suggest that selective breeding of Yamanashi strain rainbow trout with a low fishmeal diet is effective for improvement of this diet utilization.