The demand for fish and seafood globally is increasing, but wild fishing is struggling to keep pace. In this regard, aquaculture, a rapidly growing industry that provides more than half of the world’s seafood products, emerges as a response.
However, the dependence of many aquaculture species on fishmeal for their feed raises environmental and sustainability concerns, as many alternative inputs, mainly of plant origin, used to replace fishmeal have several deficiencies.
In this context, fermentation has been identified as a means to revolutionize aquaculture feed by unlocking alternative sources of proteins, improving fish health, and creating a more sustainable future for seafood products.
Scientists from Deakin University and Nord University have published a scientific review on various fermentation methods, characteristics of fermented feed ingredients, factors considered during fermentation, and the overall nutritional quality of fermented feed ingredients for aquaculture production.
The Challenge: Fishmeal and its Limitations
The growth of aquaculture is severely limited by the availability of fishmeal, as it is the main input for aquaculture feeds. The main constraints are:
- High demand, limited supply: Fishmeal prices are skyrocketing due to increased demand and overfishing.
- Environmental impact: Wild fish capture for fishmeal can harm ecosystems and contribute to overfishing.
- Nutritional limitations: Some plant-based alternatives to fishmeal lack essential nutrients or contain harmful anti-nutritional factors.
The Challenge: Finding the Right Alternatives
Replacing fishmeal requires protein sources that are:
- High in protein content: Obvious but essential for fish growth.
- Favorable amino acid profile: Certain amino acids are crucial for fish health.
- Palatable and digestible: Fish need to enjoy and efficiently utilize their food.
- Low in anti-nutritional factors (ANF): Some plant-based options contain compounds that hinder nutrient absorption.
In this context, a series of alternatives have emerged, which can be grouped into:
Plant-based options: While cheaper than fishmeal, most plant proteins fall short, as they contain ANF and have lower digestibility in carnivorous fish.
Insect meals and byproducts: Promising due to their high protein content and lack of ANF, but limitations include volume availability, potential nutritional deficiencies, and concerns about disease transmission.
Challenges of Feed Ingredients
Inputs presented as alternatives to fishmeal have several deficiencies that hinder their inclusion in aquaculture feeds:
- Anti-nutritional factors (ANF): Plant-origin proteins often contain ANF that hinder nutrient absorption in fish.
- Low nutrient bioavailability: Essential nutrients in some feed ingredients may be locked, making them unavailable to fish.
- Undigestible particles: Certain ingredients contain components that fish cannot digest, leading to nutrient waste and contamination.
- Microbial contaminants: Improper storage or processing can introduce harmful bacteria into the feed, posing a risk to fish health.
The Solution: Fermentation to the Rescue!
Fermentation, a natural process involving microorganisms such as bacteria and yeasts, offers a cost-effective and environmentally friendly way to improve various feed ingredients. It can:
- Enhance nutrient availability: Fish more easily absorb vitamins, minerals, and other nutrients.
- Increase digestibility: Fermentation breaks down complex molecules, making them easier for fish to digest, especially plant-based proteins.
- Reduce ANF: Fermentation can decrease harmful compounds like lectins and phytates, improving nutrient utilization.
- Improve intestinal health: Beneficial microbes created during fermentation can enhance digestion and immune response.
There are several experiences where inputs such as fermented soy using Bacillus, wheat fermented with fungi, and fermented corn, among others, have been employed.
The Science behind the Benefits
Different fermentation methods, such as solid-state fermentation (SSF) and submerged liquid fermentation (SLF), offer unique advantages. The choice of method depends on the specific feed ingredient and the desired outcome.
Impact on Cultivated Species
The positive effects of fermented feeds are not limited to the laboratory. Real-world studies have shown improvements in various fish species, including salmon, tilapia, carp, and shrimp, including:
- Growth performance
- Feed utilization efficiency
- Intestinal health
- Immune response
- Disease resistance
Benefits for the Aquaculture Industry
Studies cited by the review suggest that fermented feed ingredients:
- Enhance growth and feed utilization: Fish grow faster and waste less food.
- Improve intestinal health: A healthy gut microbiome leads to better digestion and disease resistance.
- Strengthen the immune system: Fermented foods can improve immune response, reducing susceptibility to diseases.
The Future of Fermented Feeds
While research is ongoing, the potential of fermented feeds for sustainable aquaculture is immense. Future areas of exploration include:
- Optimization of fermentation processes: Identifying the most efficient and cost-effective methods for different ingredients and fish species.
- Understanding intestinal health: Investigating how fermented foods affect the gut microbiome and its role in fish health and disease resistance.
- Increasing production: Developing commercially viable methods for large-scale production of fermented feed ingredients.
Conclusion
“Fermented foods are rich in dietary proteins, micronutrients, and low in ANF, playing a key role in improving somatic growth, food intake and digestibility, metabolic and digestive enzyme activities, and immune responses in fish,” conclude the scientists.
In this sense, fermentation offers a promising solution to the challenges of fishmeal dependence. By unlocking alternative protein sources, improving fish health, and reducing environmental impact, the path to a more sustainable and secure future for seafood production can be paved. This innovative approach is not only good for fish but also the planet and consumers.
Contact
David S. Francis
School of Life and Environmental Sciences, Deakin University, Geelong, VIC, Australia.
Email: d.francis@deakin.edu.au
Reference (open access)
Siddik MAB, Julien BB, Islam SMM, Francis DS. Fermentation in aquafeed processing: Achieving sustainability in feeds for global aquaculture production. Rev Aquac. 2024; 1-22. doi:10.1111/raq.12894
