The use of fishmeal (FM) in aquafeeds is considered ecologically unsustainable for the long-term development of aquaculture. Consequently, fishmeal has been largely and successfully taken out from diets of several omnivorous farmed species using substitutes from plant proteins and processed animal proteins (PAP). However, this approach has proven to be more difficult to implement in carnivorous species without affecting their growth performances and welfare. According to their levels of inclusion in aquafeeds, poultry co-products and pork blood meal have proven to be suitable substitutes to marine ingredients but further efforts are required to enhance the efficiency of those aquafeeds. In that concern, the use of feed additives, such as yeast and its derivatives, appeared to be noteworthy to counteract the adverse effects of fishmeal-free diet.
In this context, a 17% PAP-based diet (FM-free) supplemented or not with 3% of yeast extract (Prosaf®, YE) was compared to a 19% FM-based control diet in rainbow trout through a 12 weeks feeding assay. Zootechnical performances were evaluated during the feeding period and intestinal histology was assessed at the end of the trial. Moreover, transcriptomic response of distal intestine was determined through mRNA and miRNA high throughput sequencing.
The growth performances of fish fed the PAP diets were lower to those obtained with a FM-based diet. However, the addition of 3% of YE improved the efficiency of the PAP diet by significantly increasing fish growth (Tab. 1). Moreover, fish fed the YE-supplemented diet showed higher intestinal villi size (Fig. 1). Additionally, RNA-seq analysis revealed that the diets affect the expression of a small number of genes and miRNAs in the distal intestine, mainly associated with inflammation, immunity, and structure.
In conclusion, our study showed that yeast extract supplementation improved the performance of a fishmeal-free PAP diet in rainbow trout, by potentially improving nutrient absorption capacity and modulating mechanisms related to gut health, leading to better growth.