Interest of essential oils and their aromatic compounds in the development of sustainable aquaculture

Essential oils and their aromatic compounds are proven solutions to strengthen fish health. However, they remain a group of diverse molecules and a complex topic which requires knowledge and expertise. Using the correct blend to tackle challenges specific to aquaculture, Aquaviance is a dedicated solution for aquatic animals. Thanks to its mode of action, based on a strengthened gut microbiota, Aquaviance sustains growth and feed efficiency in challenging conditions. Aquaviance efficacy was proven on different species and is used all around the world, contributing to a more sustainable aquaculture.

Essential oils are well-recognized solutions to support the health of fish and reduce the deleterious effects of pathogenic bacteria. Recent publications (Sutili et al. 2017, Reverter et al. 2014, Mittal et al. 2018, Zeng et al. 2015) reviewed the multiple benefits of essential oils and their potential to provide sustainable alternatives to chemical treatments and antibiotics.

Essential oils are a generic term that refers to mixtures of various compounds, mainly terpenes and terpene derivatives, which are synthesised by plants and concentrated in hydrophobic liquids containing volatile aromatics compounds (Zeng et al. 2015). Typically, essential oils are characterized by two or three aromatic compounds in relatively high concentration (Sutili et al. 2017): Thyme’s (Thymus vulgaris) essential oil’s main aromatic compound is thymol (20 – 50%), while clove’s (Syzygium aromaticum) essential oil is mainly composed of eugenol (70 – 90%) etc. Their efficacy in reducing bacteria’s development is not a coincidence, as they are an active part of plant's defences against microbial threats. 

One of the many advantages of essential oils is their multiple bacteriostatic and bactericidal effects, depending on the quantity and quality of the aromatic compounds present in them. The array of actions is vast and includes the alteration of the membrane lipid layer, inhibition of cell division, inhibition of ATP synthesis enzymes, inhibition of quorum sensing, biofilm formation etc. (Mittal et al. 2018). These multiple actions prevent the risk of resistance by the bacteria, which represents a major concern regarding the use of antibiotics. Besides the bacteriostatic and bactericidal effects, essential oils also exert positive effects on gut bacterial communities and digestive functions, as well as anti-oxidative effects (Sutili et al. 2017).

In the late 90’s, Techna, as French company expert in animal nutrition, saw the interest of essential oils and their aromatic compounds to improve gastrointestinal health and nutrient absorption. More than 20 years of expertise and trials allowed Techna to design a new range of products based on essential oils and their aromatic compounds (Aviance for Poultry, Reganol for Pigs …). Made to answer specific problematics like productivity improvement, reduction of the occurrence of digestive disorders and anorexia... These products are used every day by feedmills and farmers all around the world.

The aquaculture industry pays a heavy toll to bacterial diseases. Conscious of that,  Techna developed a dedicated aquaculture solution, using the group's knowledge of essential oils and their aromatic compounds, to both guarantee gut health for improved nutrient absorption and act on the reduction of gut stress. Subclinical infection can lead to decreased performances, and aquatic environments are prone to variations: the product, called Aquaviance, uses the benefits of essential oils and their compounds on the microbiota to promote a favourable population, guarantee better resilience of the fish in a stressed environment and improve the overall digestive functions and feed efficacy.

Aquaviance was developed by mixing:

• Techna’s blend for maximum effects on gut bacterial community and digestive functions.
• A special mixture, designed to reduce the impact of most common pathogens in aquaculture and reduce the impact of subclinical infections. 
• The prerequisite of technological constraint in the aquaculture industry: Aromatic compounds are sensitive and volatile, which makes them difficult to use as such under commercial conditions, especially when the feed is extruded. To guarantee the lasting effect of the product after extrusion and inside the digestive tract, the product is encapsulated with a special process.

Statistical differences appeared between control and Aquaviance at 0,1% for dry matter and protein apparent digestibility and at 0,2% regarding the FCR, and protein efficiency ratio. These results are in line with a better valorisation of the feed, and this even though the diet content is high of fishmeal (46%). 

University trials are an excellent way to validate the in-vitro efficacy of feed additives, however, farm conditions are much more complex and prone to variations, challenging the mode of action of additives. Aquaviance was designed taking into account these particularities: to provide long-term effects by supporting the gut health even during transition time. Aquaviance was tested on seabream farms during two 6-month periods. From August to February, fish (IBw: 79g) treated with 1,5kg/T of Aquaviance was 25% bigger than control and had an FCR reduced by 8%. The second trial followed the first one from February to July and used other fish from the same group (IBw: 190g): Even Though the size and season are different, the results were consistent with a 13% growth increase and a 2% reduction for FCR. Used in a full L. vannamei cycle in Ecuadorian conditions, Aquaviance at 2kg/T gave better growth (+8%), survival (+7%) and lower FCR (-25%).

In both cases, besides the big differences between species and the environment, the gain of biomass and reduction of feed cost provided substantial money gains to the farmers. Aquaviance proved itself many times to be an effective tool for fish and shrimps farmers, suitable to the diverse environment and diverse species of aquaculture (Sadek S. et al., 2012 Le Than Hung et al. 2008, Calvez., 2018)

Bibliography

• Sutili. F.J., Gatlin D.M et al., 2017, plant essential oils as fish diet additives: benefits on fish health and stability in feed.
• Reverter. M., N. Bontemps, D. Lecchini, B. Banaigs, P. Sasal et al., 2014, Use of plant extracts in fish aquaculture as an alternative to chemotherapy: Current status and future perspectives.
• Mittal P. R, Rana A, Jaitak V., 2018, Essential oils: An impending substitute of synthetic antimicrobial agents to overcome antimicrobial resistance.
• Zend Z., Zhang S., Wang. H. et al., 2015, Essential oil and aromatic plants as feed additives in non-ruminant nutrition : a review
• Min-Gi K., Chorong L., Le Reste G. et al., 2014, Evaluation of a mixture of essential oils and prebiotic in diets for olive flounder, Paralichthys olivaceus. (not published)
• Le Thanh Hung, Vo Thi Than Bin, 2008, AQUAVIANCE improves growth performance and feed intake for Pangasius catfish (Pangasius hypophthalmus). (not published)
• Aly S.M, Sadek S.S, Lucien Brun H., 2012, Evaluation of Aquaviance as a commercial product to optimize and enhance the nile tilapia (O. niloticus) performance in aquaculture. (not published)
• Calvez S., 2018, Test de l’efficacité de différents additifs avec un aliment classique sur la croissance de truites arc-en-ciel (O. mykiss). (not published)
• Calvez S., 2014, Minimum Inhibitory (MIC) and Minimum Bactericidal Concentration (MBC) Evaluations of Aquaviance on various pathogenic strains.