Spent Oyster Mushroom Substrate Enhances Tilapia Health and Growth in Aquaculture Feeds
- Marc Violo
- 4 days ago
- 3 min read
As aquaculture continues to grow, the industry is under increasing pressure to improve fish health while reducing reliance on antibiotics and expensive feed inputs. A recent review published in the Latin American Journal of Aquatic Research suggests that one promising solution may be found in an unlikely source: spent oyster mushroom substrate (SOMS).
From Waste to Feed Ingredient
SOMS is the fibrous by-product left behind after cultivating oyster mushrooms (Pleurotus spp.). For every kilogram of mushrooms harvested, around five kilograms of SOMS are generated. Traditionally viewed as agricultural waste, SOMS contains residual mycelium rich in protein, antioxidants, and immunostimulatory compounds. These properties make it a potential additive in aquaculture feeds—particularly for Nile tilapia (Oreochromis niloticus), a widely farmed species known for its adaptability and herbivorous diet. This fish is by far the most widely farmed tilapia species, accounting for over 70% of global production. It's native to Africa and the Middle East, and prized for its fast growth rate, reaching marketable size in just 6-12 months. Nile tilapia are also tolerant of a wide range of water conditions, making them adaptable to different farming systems.
Nutritional Value and Digestibility
Oyster mushroom mycelium breaks down lignocellulosic materials during growth, improving the digestibility and nutritional quality of the remaining substrate. Studies have shown increases in SOMS protein content of up to 2,000% compared to the raw material. Rich in essential amino acids and bioactive compounds such as β-glucans and phenolics, SOMS could serve as both a protein source and functional ingredient in fish diets.
However, its fibre content remains relatively high. For tilapia alevins, crude fibre levels above 9% can reduce protein efficiency and weight gain. Formulations would need to limit SOMS inclusion or combine it with fermentation or processing techniques to improve digestibility.
Bioactive Properties for Health Promotion
One of SOMS’s most valuable contributions may lie in its functional properties. Oyster mushroom by-products are known to contain phenolic antioxidants and β-glucans with antimicrobial and immunomodulatory activity. These compounds can help fish resist disease and oxidative stress, reducing the need for antibiotics.
In particular, β-glucans from Pleurotus species, also known as pleuran, have been shown to stimulate immune markers like lysozyme, phagocytic activity, and cytokine expression in tilapia. Oral administration via feed is the most practical and scalable method, especially when the whole SOMS matrix is used instead of extracts.
Microbiome Modulation and Prebiotic Potential
SOMS may also have prebiotic effects, influencing the gut microbiota of farmed fish. Studies with β-glucans have shown increased diversity and abundance of beneficial bacterial genera in the fish gut, contributing to better nutrient absorption and immune function. While more research is needed to verify this in SOMS specifically, the early evidence is promising.
Inclusion in Feed Trials
Experimental diets using mushroom meal or SOMS have shown positive effects on fish growth and feed efficiency. Substitution of maize or fishmeal with Pleurotus-derived products has been tested at rates of up to 25%, with no adverse effects on growth performance. A study using SOMS fermented with lactic acid bacteria achieved a crude protein content of 42%, demonstrating the potential to enhance its value through biotechnological processing.
Another feeding trial using SOMS with rice straw in tilapia diets showed that up to 20% inclusion was safe and effective. However, further studies are needed to optimise formulation, particularly in relation to fibre levels and bioactive compound concentrations.
Outlook and Considerations
Spent oyster mushroom substrate represents a low-cost, nutrient-rich by-product that could help reduce feed costs and improve fish health in tilapia aquaculture. Its bioactive properties—especially antioxidant and immunostimulatory effects—warrant further exploration, particularly as the industry looks for sustainable alternatives to synthetic additives and antibiotics.
As aquaculture moves toward more circular models of production, turning mushroom waste into functional feed ingredients could be one way to close the loop.
Citation
García-Aguirre, J.I., Hernández, C., & Esqueda, M. (2025). Spent oyster mushroom substrate as a potential bioactive and nutritional food ingredient for tilapia culture: a review. Latin American Journal of Aquatic Research, 53(2), 209–225. https://doi.org/10.3856/vol53-issue2-fulltext-3330
