Drew: Effect of yeast-fermentation and extrusion of canola meal on digestibility and growth performance of rainbow trout and Nile tilapia
Date: April 2017
Term: 2 years
Status: Completed
Researcher(s): Murray Drew, Chuyuan Zhang, University of Saskatchewan, Saskatoon SK
SaskCanola Investment: $195,848
Total Project Cost: $195,848
Funding Partners: n/a
Project Summary
Canola meal (CM), a by-product of canola crushing, is the primary high-protein ingredient in Western Canada that is used as a protein supplement in feed rations for livestock, and being evaluated as an ingredient in fish diets. Researchers at the University of Saskatchewan conducted a two-year project to examine the effects of feeding enzyme pre-treated and yeast-fermented canola meal (FMC) on the nutrient digestibility and growth performance of Nile tilapia and rainbow trout. Overall, the study results showed that FMC can be used in diets for herbivorous and omnivorous fish such as Nile tilapia without negative effects on growth of fish. However, there may be concerns using FMC as fishmeal replacer in carnivorous fish diets, such as rainbow trout.
Canola meal (CM), a by-product of canola crushing, is the primary high-protein ingredient in Western Canada that is used as a protein supplement in feed rations for livestock. Plant protein sources are also being evaluated as fishmeal replacements in fish feed to improve sustainability of the aquaculture industry. Although the cost of CM protein is approximately half that of fishmeal per unit protein basis, and the protein efficiency ratio of CM protein is high, the use of canola/rapeseed meal in fish feed is limited due to its low nutrient digestibility and adverse effects on fish growth.
Researchers at the University of Saskatchewan conducted a two-year project to examine the effects of feeding enzyme pre-treated and yeast-fermented canola meal on the nutrient digestibility and growth performance of Nile tilapia and rainbow trout. Nile tilapia represent an omnivorous, warm-water species, which is reputed to be less sensitive to the effects of canola antinutritional factors (ANFs). Rainbow trout represent a carnivorous, cold-water species that is known to be sensitive to ANFs present in CM. The objective of the study was to determine the effect of extrusion combined with Candida utilis fermentation of CM on the nutrient digestibility, growth performance and intestinal inflammation and function in Nile tilapia and rainbow trout.
The project began with a meta-analysis of published results of the effects of feeding fermented plant-derived ingredients (FPIs) on the specific growth rate (SGR) of carnivorous, omnivorous and herbivorous fish species. From 1176 studies identified, 29 studies were applied in the meta-analysis. The results showed that replacing fishmeal (FM) with FPIs had significantly negative effect on SGR of carnivorous fish. By contrast, FPIs showed a significantly positive effect on SGR of herbivorous and omnivorous species when replacing the unprocessed raw ingredients (RI) in their diets. The results suggest that fermented plant proteins could be used in diets for herbivorous and omnivorous fish without negative effects on growth, however, there may be concerns when using fermented plant proteins as fishmeal replacer for carnivorous fish.
In the second part of the project, canola meal was fermented with Candida utilis and evaluated as an ingredient in diets for Nile tilapia and rainbow trout. C. utilis is an industrially important yeast, which has been used as nutritional supplements in animal feeds for many years. The fermentation process resulted in a fermented canola meal (FMC) ingredient with increased amino acid content and decreased glucosinolates and phytate.
Two trials were conducted with Nile tilapia and rainbow trout to investigate the digestibility of CM or FCM as compared to fishmeal in a reference diet. The trial compared three diets, a reference diet with 30% fishmeal or 30% CM or 30% FMC. The results showed that fermented canola meal had significantly higher crude protein digestibility in rainbow trout, whereas there were no significant differences on nutrient digestibility in Nile tilapia.
Subsequently, two eight-week feeding trials were conducted to examine the impact of feeding various levels of CM or FCM on the growth performance of Nile tilapia and rainbow trout. In the Nile tilapia study, the results showed that the CM inclusion rate had a significantly negative trend on final fish weight (FW) and average daily gain (ADG). However, FCM could be successfully included in diets at rates of up to 600 g/kg without compromising Nile tilapia growth. In the rainbow trout trials, the results showed that the fermentation process significantly improved the growth performance of rainbow trout compared with unprocessed CM, however the inclusion of CM or FCM did have significantly negative effects on FW, ADG, specific growth rate (SGR) and feed conversion ratio (FCR) as compared to fishmeal reference diets.
Overall, the study results support the meta-analysis, suggesting that FMC can be used in diets for herbivorous and omnivorous fish such as Nile tilapia without negative effects on growth of fish. However, there may be concerns using FMC as fishmeal replacer in carnivorous fish diets, such as rainbow trout.