With the increasing tendency to replace fish-derived proteins with more cost-effective plant materials, the topic of mycotoxins in aquaculture production is gaining ever-greater relevance. Mycotoxins are very strong immunomodulatory compounds and have negative effects on aquatic farmed species. This matters because when it comes to production in closed systems with high stocking density, a healthy immune system can be a game changer that ensures robust production.
Protecting the immune system results in stronger growth, increased resistance to environmental stressors and to pathogens. A healthy animal will utilize all the energy derived from the feed for growth and will not need to waste any of it trying to recover from stress. Moreover, immune protection will help to reduce the number of treatments such as antibiotics and other chemicals.
When it comes to mycotoxin management, immunomodulation and fish farming, there are five parameters that we want to keep in mind:
1. Water quality matters
The water quality of ponds and closed system is generally not that great. The use of fertilizers and the exchange of water that is mostly limited to rainfall or through pumping from external water bodies that may be polluted, together with high stocking density and rapid shifts in temperature, all contribute to poor water quality. This acts as a stressor on animals and creates an ideal environment for the proliferation of pathogens. Mycotoxins can contribute to render pathogenic infections more severe through synergistic interactions.
2. Serious diseases abound
Some aquatic species are robust (e.g. tilapia) but are still susceptible to a great number of parasites. Trichodinosis, argulosis, epitheliocystis, streptococcosis, francisellosis and a variety of viral diseases such as herpes-like virus, betanovirus, etc., can have a considerable impact on production. Some of these diseases are still under investigation, other appeared in recent years (first report on reo-like virus in tilapia was in 2008).
3. Routine management causes stress
Stresses caused by manipulation (e.g. egg collection, routine pond maintenance operations, etc.) can leave aquatic species stressed and even wounded—with negative effects on the immune system, feed intake and feed efficiency. The presence of mycotoxins in the diet – even at low doses - can greatly aggravate these effects.
4. Plant-based feed ingredients carry additional risks
Feed represents the majority of the cost in aquaculture—more than 70% of costs for some species. Poor quality feed and overfeeding can affect performances, the immune system and biosecurity—creating the conditions for disease outbreaks and productivity losses. The inclusion of plant sources will decrease the price of feed but will expose animals to new challenges, including mycotoxins. Among these toxic substances, aflatoxins and trichothecenes are potent carcinogens are immune-modulators in aquatic species.
5. Co-contamination is common
Focusing on only one mycotoxin is not an ideal strategy. Feed commodities are typically contaminated by several mycotoxins at the same time. The reason is that different fungi grow on grains at different stages: some on the field, some during storage. Furthermore, production of mycotoxins is related to environmental factors such as drought, precipitation, temperature, etc.
Science-based solutions can help fish producers to achieve their ambitious goals. Protecting the immune system of fish from stressors and mycotoxins may represent the key to profitable production.
Using a registered product with a broad spectrum of action will ensure absolute protection against the adverse effects of mycotoxins, boost the immune system and gastrointestinal health. Doing so will also generate a great return of investment in the mid-term, thanks to better feed utilization. This approach could offer a valuable way for producers to pursue profitable, sustainable aquaculture production.