Austrian researchers have developed and tested a simplified, single-step method for disinfecting non-hardened rainbow trout (Oncorhynchus mykiss) eggs that could replace the traditional two-step iodophore treatment used in salmonid aquaculture.
The study, led by Franz Lahnsteiner and Anna Dünser from the Federal Agency for Water Management and Fishfarm Kreuzstein, found that fertilization and disinfection can be carried out simpultaneous by immersing eggs in a 0.75% NaCl solution containing either 100mg/L Chloramine Chloramine T® (tosylchloramide) or 100 µL/L Wofasteril® (a peroxide-based compound) for 40 minutes.
The researchers report that these concentrations have minimal effects on sperm motility and do not negatively impact embryo development, larval survival, or growth. Both disinfectants were as effective as the conventional iodophore product Buffodine® in reducing bacterial loads at three hours post-fertilisation, while Chloramine T showed superior results after 22 days of development.
Analysis of the eggs’ microbiome revealed significant differences in bacterial community composition between treatments and over development stages. Buffodine increased bacterial diversity, whereas Chloramine T and Wofasteril reduced it. The authors note that microbiome stability and resilience are important for long-term fish health, and that disinfectants should be evaluated not only for pathogen reduction but also for their influence on beneficial microbial communities.
From an operational perspective, the one-step method could streamline handling during large-scale egg stripping, reducing time-sensitive processes and the risk of fertilization errors. It may also offer environmental benefits, as Chloramine T and Wofasteril are applied at much lower concentration than iodophores, degrade rapidly in water, and leave no harmful residues.
The authors conclude that the method is a practical and environmental preferable alternative, particularly relevant as the continued approval of iodophore-based products in the EU in under review.
Reference:
Franz Lahnsteiner, Anna Dünser. A simplified, one step technique for disinfection of non-hardened rainbow trout eggs with tosylchloramide (Chloramine T) and peroxide (Wofasteril) compounds and the effects on bacterial load and microbiome composition in comparison to iodophore disinfection. Journal of Genetic Engineering and Biotechnology, Volume 23, Issue 3, 2025, 100541, ISSN 1687-157X https://doi.org/10.1016/j.jgeb.2025.100541
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One-step disinfection method for rainbow trout eggs shows operational and environmental advantages
Austria, 14 August 2025 | Austria, 14 August 2025 | New protocol simplifies large-scale egg handling and cuts chemical impact by using lower concentrations of rapidly degradable disinfectants
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