Oregano Essential Oil: An Ally for the Growth and Health of Rainbow Trout

Photo of author

By Milthon Lujan

Trout. Source: INRAE
Trout. Source: INRAE

The aquaculture industry plays a crucial role in global food production, providing a significant source of protein. In this context, the search for natural alternatives to enhance the growth and disease resistance of cultivated species is an ongoing objective.

A study published by scientists from Qingdao Agricultural University and Ecopharm Hellas SA has shed light on the potential of oregano essential oil (OEO) in improving growth, amino acid composition, and resistance to pathogens in rainbow trout.

The Study

The study in question evaluated the effects of dietary supplementation of rainbow trout with OEO on intestinal microbiota, amino acid composition, and resistance to Aeromonas salmonicida.

To conduct the research, 480 fish were divided into four feeding groups: a control group without supplementation and three groups supplemented with different concentrations of oregano essential oil (2.0, 4.0, and 8.0 mL OEO/kg).

Growth and Amino Acid Composition

The results revealed several notable benefits associated with the use of OEO in rainbow trout feeding.

One of the most prominent findings was the positive impact of OEO on the growth performance of rainbow trout.

Fish supplemented with OEO showed a higher deposition of amino acids in the muscle, which has significant implications for meat quality and protein production. Furthermore, a significant enrichment in amino acid pathways was observed, suggesting an improvement in nutrient utilization in the fish’s diet.

Intestinal Microbiota

The composition of intestinal microbiota is a key factor in the health of aquatic organisms. Oregano essential oil demonstrated a positive impact in this regard by increasing the abundance of Proteobacteria and reducing that of Firmicutes in the intestinal microbiota of rainbow trout.

See also  Aquatic biodiversity key to sustainable, nutrient-rich diets

This beneficial shift in bacterial composition was associated with an increase in beneficial bacteria such as Streptococcus lutetiensis, Oscillospirales, and Methylobacterium-Methylorubrum, and a decrease in potential pathogens like Mycoplasma, Morganellaceae, and Paenalcaligenes.

Immunity and Pathogen Resistance

OEO also showed a positive impact on the immune response of rainbow trout.

An upregulation of various genes related to immunity was observed, indicating an improvement in the fish’s defense capability. At the same time, a downregulation of genes such as il-6, il-21, and il-34, which are associated with excessive inflammatory responses, was recorded.


In summary, oregano essential oil has emerged as a promising dietary supplement in rainbow trout aquaculture. This pioneering study highlights the positive effects of OEO on growth, amino acid composition, and resistance to pathogens in rainbow trout.

The beneficial changes in intestinal microbiota and the improvement in immune response underscore its potential as a tool to promote the health and sustainable production of fish in the aquaculture industry.

However, it is important to note that further research is needed to fully understand the mechanisms behind these effects and their applicability in different species and cultivation environments.

Yichao Ren
School of Marine Science and Engineering
Qingdao Agricultural University
17 Wenhai Road, Aoshanwei, Jimo, Qingdao, 266109, China
Email: yichaor@126.com

Reference (open access)
Dang, Y., Zhao, C., Kuan, K.C.S. et al. Effects of dietary oregano essential oil-mediated intestinal microbiota and transcription on amino acid metabolism and Aeromonas salmonicida resistance in rainbow trout (Oncorhynchus mykiss). Aquacult Int (2023). https://doi.org/10.1007/s10499-023-01246-w

Leave a Comment