ADDITIVES

Onion-Derived Compounds Show High Potential as Functional Feed Additives for Salmonids and Gilthead Seabream

El Puerto de Santa María, Spain, 30 October 2025 | Organosulphur compounds from onions can improve survival rates and growth, and reduce the incidence of parasites in salmonids and gilthead seabream

Cebolla roja

Organosulphur compounds from the onion (Allium cepa) possess significant antimicrobial and antiparasitic activity relevant to aquaculture, proving effective when included as functional additives in aquafeed.

Sector-applicable studies, led by José Cabello Gómez, Director of Experimental Development at Technological Aquaculture Centre (CTAQUA), in Spain, back this potential. Their work has demonstrated that when included as a feed functional additive for salmonids like rainbow trout (Oncorhynchus mykiss) or Atlantic salmon (Salmo salar), as well as gilthead seabream (Sparus aurata), these compounds significantly improve the survival rate and bring about a substantial reduction in parasitic load.

Specifically, these compounds are Propyl-Propane-Thiosulphonate (PTSO) and Propyl-Propane-Thiosulphinate (PTS). Both can help protect fish against bacteria, fungi, and parasites, contributing to a more sustainable and resilient aquaculture when integrated with good management practices. The Propyl-Propane-Thiosulphonate was identified as the compound with superior performance.

Results Validate in High-Impact Journals

The research was supported by rigorous in vitro and in vivo studies, carried out in Granada, El Puerto de Santa María (Spain), and Puerto Montt (Chile).

The study on salmonids is the most recent. According to CTAQUA, the centre informed misPeces that the paper was published in the scientific journal Aquaculture on 19 August 2025, titled: “Antimicrobial and antiparasitic activity of propyl-propane-thiosulfinate (PTS) and propyl-propane-thiosulfonate (PTSO) from Allium cepa against salmonid pathogens”.

As detailed by José Cabello, co-author of the publication, this study “demonstrates, practically, that the supplementation of the diet with PTS/PTSO improves the survival of rainbow trout against relevant pathogens for the sector, such as Aeromonas salmonicida, Yersinia ruckeri, and the fungus Saprolegnia parasitica.”

In the case of Atlantic salmon, diets enriched with these compounds reduced the burdens of sea lice (Caligus rogercresseyi), showing a clear preventive effect in early stages (copepodites) and improvements in chalimus stages.

This line of work follows on from a previous publication concerning gilthead seabream in the journal Molecules, where the additive also proved to increase the survival rate against the bacterial challenge of photobacteriosis and reduce the gill parasite.

The Future of Aquaculture Health

Collectively, the results indicate lower disease-related losses and support the preventive use of these natural organosulphur compounds within integrated aquatic animal health programmes. This reinforces the evidence that they are alternative with the potential to reduce the use of chemical antibiotics and antiparasitics.

“In the next phase, we will expand with trials against other key pathogens in Mediterranean species and delve deeper into the microbiota and immunomodulation, analysing the impact of PTS/PTSO on the intestinal microbiota of European seabass (Dicentrarchus labrax) and immune markers associated with sanitary resilience,” Cabello concluded.

References:

  1. Cabello-Gómez, J.F., Aguinaga-Casañas, M.A., Falcón-Piñeiro, A., Mut-Salud, N., Agraso, M. del M., González-Gragera, E., García-López, J.D., Núñez, C., Latuz, S., Asencio, G., Martínez-Bueno, M., Baños, A., 2026. Antimicrobial and antiparasitic activity of propyl-propane-thiosulfinate (PTS) and propyl-propane-thiosulfonate (PTSO) from Allium cepa against salmonid pathogens. In vitro and in vivo studies. Aquaculture 611, 743075. https://doi.org/10.1016/j.aquaculture.2025.743075

  2. Cabello-Gómez, J.F., Aguinaga-Casañas, M.A., Falcón-Piñeiro, A., González-Gragera, E., Márquez-Martín, R., Agraso, M. del M., Bermúdez, L., Baños, A., Martínez-Bueno, M., 2022. Antibacterial and Antiparasitic Activity of Propyl-Propane-Thiosulfinate (PTS) and Propyl-Propane-Thiosulfonate (PTSO) from Allium cepa against Gilthead Sea Bream Pathogens in In Vitro and In Vivo Studies. Molecules 27, 6900. https://doi.org/10.3390/molecules27206900