ATLANTIC SALMON (Salmo salar) SMOLTS FED DIETS CONTAINING PROPLEX, A YEAST PROTEIN PRODUCT

Atlantic salmon (Salmo salar) is an important cultured carnivorous species and the feed for this species has increasing amounts of alternative proteins.   Atlantic salmon have been shown to have slightly reduced, but not significantly lower, performance when fed diets that were fishmeal-free and contained wheat gluten, corn gluten, fish solubles, and crystalline amino acids.  Amino acid supplementation is often needed to maintain growth performance of fish fed plant protein-based feeds.  This study examined the effects on the yeast protein Proplex on the growth performance of Atlantic salmon.

A digestibility study was conducted using ~500-g Atlantic salmon. The apparent digestibility coefficients (ADCs)of macro nutrients in Proplex yeast product was higher for organic matter and dry matter, but lower for protein compared to menhaden fishmeal. The lysine ADC for Proplex was lower compared to fishmeal while the methionine ADC was higher compared to fishmeal.  After the conclusion of the digestibility trial, a 16-week growth trial was conducted.  Atlantic salmon smolts were grown in a recirculating aquaculture system. The Proplex diets did not affect salmon growth when included in the diet up to 15% (Table 1).  Average final weight ranged from 395g to 446g, weight gain ranged from 237% to 292%, feed conversion ratios ranged from 0.85 to 1.1, and specific growth rate ranged from .93%/day to 1.08%/day.  The feed conversion ratios was in the range we normally see for fish of this size with most gaining more weight than feed consumed. The proximate composition of the fish was not affected by the yeast product, except for the ash content of fish fed the 15% inclusion diet.  Percent ash did vary significantly and ranged from 1.8% to 2.5%.  The proximate composition did not differ from previous experiments.  Overall including Proplex at 15% of the diet did not affect Atlantic salmon performance during this sixteen week study.