Replacing fishmeal with blends of alternative proteins on growth performance of rainbow trout (Oncorhynchus mykiss), and early or late stage juvenile Atlantic salmon (Salmo salar)

The purpose of this study was to evaluate blends of alternate proteins as replacements for fishmeal in diets for rainbow trout (Oncorhynchus mykiss) and to use the results to develop and test alternate protein blends in diets for juvenile Atlantic salmon (Salmo salar). Nine experimental diets in which protein blends replaced 63%, 82% or 100% of fishmeal in the formulation (20, 10, and 0% fishmeal) were fed to rainbow trout (initial weight 19.5g) for 12weeks. Weight gains of trout fed diets containing the soy protein concentrate-based blend and the fishmeal control diet were similar, except at the 100% fishmeal replacement level, and significantly higher than that of trout fed diets containing the other blends. The soy protein blend and another based on wheat gluten meal were modified slightly and evaluated in early stage Atlantic salmon juveniles (initial weight 5.5g). Protein blends replaced 50%, 66% or 84% of fishmeal (30, 20 or 10% fishmeal). Weight gains of early stage juvenile salmon after 18weeks of feeding were significantly lower and feed conversion ratios higher when fed diets containing either blend compared to the fishmeal control diet, and gains decreased as level of fishmeal replacement increased. Blends were then modified further and tested in advance stage salmon juveniles (initial weight 31.5g). These blends were solely either all-plant protein-based or contained poultry by-product meal. Both blends were evaluated with or without addition of Spirulina algae meal. Alternate protein blends completely replaced fishmeal in experimental diets. After 12weeks of feeding, no differences in weight gain or feed conversion ratios were measured among groups fed experimental diets containing protein blends or the fishmeal control diet. Replacement of fishmeal with alternative protein blends in diets for early stage juvenile salmon is not recommended and the penalty in growth is severe. Fishmeal can be completely replaced in diets for late stage salmon over 30g without compromising fish performance or using land animal protein ingredients in feed formulations. ► Alternate protein blends were evaluated in rainbow trout and juvenile Atlantic salmon. ► Rainbow trout growth was best using a soy protein concentrate blend. ► Early stage juvenile Atlantic salmon performed poorly on all blends. ► Late stage juveniles performed well on an all-plant protein diet. ► Plant-protein blends can replace 100% of fishmeal in feeds for large juvenile salmon.