Evaluation of family growth response to fishmeal and gluten-based diets in rainbow trout ( Oncorhynchus mykiss)

A study was conducted to evaluate genotype × feed interactions in a commercial strain of rainbow trout ( Oncorhynchus mykiss). Microsatellite DNA markers were used to determine the pedigree of the top 1% and bottom 1% of progeny in a large scale commercial growth trial of 24,000 rainbow trout from 20 full-sib families (20 dams × 10 sires in a nested mating design). The progeny were pooled at eyed stage and divided into 2 groups. Half of the fish from each family were fed a standard fishmeal-based diet and the other half was fed a plant protein (gluten)-based diet to determine the relative family rankings in each diet. The primary protein sources in the plant protein-based diet were corn gluten and wheat gluten meals. Krill was supplemented to this feed for the early life stages (starter, #1, #2, #3 crumbles), but was eliminated in the larger pellet sizes. Large genetic variation for growth was identified for both diets and the sire effect was found to be highly significant ( P < 0.001). The family rankings were similar for both diets, which suggest that the fish that grow faster on fishmeal diet are likely to grow faster on plant protein-based diets, and therefore current commercial strains that exhibit superior growth should retain their improved performance if raised on gluten-based diets. Multiplexing microsatellite markers would further improve the efficiency of parentage assignment protocols in large-scale rainbow trout selection programs.