Research & Insights
Brewer's Yeast in Trout and Salmonid Feed: Trial Levels and Formulation Notes
Published
In short: in rainbow trout, brewer's dried yeast at 25% of the diet gave faster growth and better feed conversion than the control (Rumsey et al., 1991). A 2020 study replaced up to 40% of fishmeal with Saccharomyces cerevisiae yeast on a digestible protein basis without loss of growth, nutrient digestibility or intestinal health.
This brief is for aquafeed nutritionists, R&D teams and ingredient buyers working on trout and salmon diets in Europe, the UK, Japan, North America and Oceania.
Why are salmonid formulators looking at yeast protein?
Salmonid diets rely on fishmeal more than most aquafeeds, and fishmeal supply depends on wild catches and quotas. Our fish meal market note covers the current pricing pressure. Formulators want protein sources that are consistent, traceable and easier to defend in sustainability reporting.
Brewer's yeast is a co-product of beer production. Spent yeast recovered from breweries and dried becomes a feed ingredient instead of a waste stream, an upcycling story that matters to buyers and retailers in the EU and UK.
How do salmonids handle yeast nucleic acids?
Yeast is rich in nucleic acids, mostly RNA. Salmonids handle them well: they have a very active liver uricase, which breaks down the uric acid formed from dietary purines, so they can process high dietary nucleic acid levels (Rumsey et al., 1991; Kinsella et al., 1985, cited in Feedipedia).
In the Rumsey trial, liver uricase activity rose as dietary nucleic acid increased, and the authors found no clear physiological harm from the high RNA intake. Nucleotides from yeast are also studied as a functional component in young fish, together with beta-glucans and mannan-oligosaccharides (MOS) from the cell wall.
What do rainbow trout trials report?
| Study | Yeast | Level tested | Main reported result |
|---|---|---|---|
| Rumsey, Kinsella, Shetty and Hughes (1991), Animal Feed Science and Technology | Brewer's dried yeast | 0, 25, 50 and 75% of diet | Faster growth and more efficient feed conversion at 25% than the control; 25% was the best level in the trial |
| Vidakovic et al. (2020), Aquaculture Nutrition 26(2) | S. cerevisiae, and a W. anomalus and S. cerevisiae mix | 20, 40 and 60% of fishmeal replaced, digestible protein basis; control 300 g/kg fishmeal; 10 weeks | Up to 40% of fishmeal replaced without compromising growth, digestibility or intestinal health |
| Feedipedia datasheet, brewers yeast | Brewer's yeast | Fishmeal protein replacement | Up to 50% of fishmeal protein replaced; up to 30% replacement associated with better feed efficiency |
The trials use two units. Rumsey reports yeast as a share of the whole diet. Vidakovic reports the share of fishmeal replaced on a digestible protein basis. A buyer comparing suppliers' claims should check which unit is meant before reading the number.
How should a trout diet be formulated with brewer's yeast?
Start from digestible values, not crude values. Feedipedia lists nitrogen digestibility of 77.1% and digestible energy of 13.7 MJ/kg dry matter for brewer's yeast in salmonids, based on a small number of measurements. Researchers link the digestibility of single-cell proteins to the structure of the yeast cell wall (Rumsey et al., 1990, cited in Feedipedia).
| Formulation step | Practical note |
|---|---|
| Set the target | Replace 20 to 40% of fishmeal on a digestible protein basis, in line with Vidakovic et al. (2020) |
| Check intake | In Rumsey et al. (1991) the best growth and feed conversion came at 25% of the diet |
| Balance amino acids | Yeast lysine is about 6.3% of protein; methionine is lower, so balance it from other ingredients |
| Watch pellet quality | Fine, evenly milled yeast disperses evenly in extruded feed; confirm with a pellet durability and water stability test |
The full amino acid table is in our amino acid profile guide. For a direct comparison with marine protein, see brewer's yeast versus fish meal in shrimp feed, which uses the same digestible-basis logic.
Which markets ask for which documents?
Trout and salmon feed producers in the EU and UK usually ask about sustainability, feed material status and supply consistency. Japanese buyers expect detailed QA files: specification, safety data sheet, certificate of analysis and a precise description of the process. North American and New Zealand buyers tend to start with the specification sheet and a trial quantity. We prepare the same core document set for all of them.
TBESBY dried brewer's yeast for aquafeed
TBESBY is made from fresh brewer's yeast from leading international breweries in Vietnam, drum-dried at our own facilities in Vietnam. The process is receiving, drum drying, milling and sieving, packing, with laboratory testing. The specification is 40 to 46% crude protein, moisture below 10%, ash below 6%, fat max 0.5%, fibre max 1.5% and lysine 30.5 g/kg, with a 12-month shelf life. Packing is 25 kg bags or 600 to 1,200 kg jumbo bags. TBESBY is U.S. FDA registered, certified to ISO 22000:2018 and non-GMO.
Application notes for fish and shrimp are on our aquafeed page, and the full specification is on the product page. Global standards. Direct from our own facilities.
Frequently asked questions
How much brewer's yeast can rainbow trout diets contain?
In Rumsey et al. (1991), 25% of the diet gave the best growth and feed conversion. Vidakovic et al. (2020) replaced up to 40% of fishmeal on a digestible protein basis without loss of performance.
Why can salmonids use yeast with high RNA content?
Salmonids have a very active liver uricase, which breaks down the uric acid formed from dietary purines. This lets them process the nucleic acids in yeast efficiently.
Is brewer's yeast a sustainable aquafeed ingredient?
It is a co-product of brewing that would otherwise need disposal. Drying it for feed is an upcycling route that reduces dependence on wild-caught fishmeal.
Does yeast affect pellet quality in extruded trout feed?
Fine, evenly milled yeast disperses well, but each formula should be checked for pellet durability and water stability before scale-up.
Sources
- Rumsey, G.L., Kinsella, J.E., Shetty, K.J. and Hughes, S.G. (1991). Effect of high dietary concentrations of brewer's dried yeast on growth performance and liver uricase in rainbow trout (Oncorhynchus mykiss). Animal Feed Science and Technology. https://doi.org/10.1016/0377-8401(91)90058-Z
- Vidakovic, A., Huyben, D., Sundh, H., Nyman, A., Vielma, J., Passoth, V., Kiessling, A. and Lundh, T. (2020). Growth performance, nutrient digestibility and intestinal morphology of rainbow trout (Oncorhynchus mykiss) fed graded levels of the yeasts Saccharomyces cerevisiae and Wickerhamomyces anomalus. Aquaculture Nutrition, 26(2), 275-286. https://doi.org/10.1111/anu.12988
- Feedipedia (INRAE, CIRAD, AFZ, FAO). Brewers yeast datasheet, including Rumsey et al. (1990) and Kinsella et al. (1985). https://www.feedipedia.org/node/72
Planning a trout or salmon feed trial? Ask for the specification sheet and a quote.