Effect of plant protein sources on growth rate in salmonids: Meta-analysis of dietary inclusion of soybean, pea and canola/rapeseed meals and protein concentrates

• The effect of plant proteins on salmonid growth was determined using meta-analysis.
• The use of Cohen’s d allows comparisons of growth results among studies.
• As the inclusion rate of soy and canola products increase, SGR decreases.
• Pea products do not have a significant impact on growth at these reported levels.

Six parallel meta-analyses were conducted to determine the effect of the dietary inclusion rate of pea meal (PM), pea protein concentrate (PPC), soybean meal (SBM), soy protein concentrate (SPC), canola/rapeseed meal (CM) and canola/rapeseed protein concentrate (CPC) on the specific growth rate (SGR) of salmonid fish. From 1794 growth studies involving the feeding of these six test ingredients to salmonid fish, 45 studies were selected for inclusion in the meta-analysis. The relationship between SGR and the dietary inclusion level of plant-based feed ingredients was calculated using Cohen's d (CD), which measures differences between control and experimental means. The results of these meta-analyses showed an increase in the dietary inclusion of SBM, SPC, CM and CPC (not PM or PPC) leads to a significant reduction in SGR. Weighted regressions of inclusion level for each test ingredient on effect size showed significant, negative linear relationships between SGR and dietary inclusions of SBM, SPC, CM and CPC. For PM and PPC, there was no significant relationship between SGR and inclusion rate. The results suggest that the effect of plant ingredients on growth performance of salmonids depends on the specific ingredients and their inclusion levels. The higher effect sizes observed when ingredients are fed at lower inclusion levels and lack of significant impact of feeding mixed diets suggest that feeding low levels of several ingredients might be beneficial.