Interest of essential oils and their aromatic compounds in the development of sustainable aquaculture
by Jean Peignon, Aquaculture Nutritionist, Aquaneo, Techna France Nutrition
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 to aquatic animals. Thanks to its mode of action, based on a strengthen gut microbiota Aquaviance sustains the 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.
Origin and effects of essential oils and their aromatic compounds
Essential oils are well-recognis ed 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 is a generic term that refers to mixtures of various compounds, mainly terpenes and terpene derivatives, which are synthetised by plants and concentrated in hydrophobic liquids containing volatile aromatics compounds (Zeng et al 2015). Typically, essential oils are characterised 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 to reduce bacteria's development is not a coincidence, as they are an active part of plants 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 it. The array of action is vast and includes the alteration of 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 represent a major concern regarding the use of antibiotics. Beside 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).
Techna: Years of expertise in precision nutrition
In the late 90's, Techna, a French company experienced 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 product based on essential oils and their aromatic compounds (Aviance for poultry, Reganol for pigs ...). These solutions were made to answer specific problems such as productivity improvement without antibiotic growth promoters, fighting weaning stress, digestive disorders and anorexia. These products are used every day by feedmills and farmers all around the world.
The aquaculture industry suffers a heavy toll due to bacterial diseases. Conscious of that, Aquanéo, the aquaculture brand of Techna, developed a dedicated solution, using the group knowledge of essential oils and their aromatic compounds, to both guarantee gut health for improved nutrient absorption and reduce gut stress. Subclinical infections can lead to decreased performances, and aquatic environments are prone to variations. Aquanéo's product, Aquaviance, uses the benefits of essential oils and their compounds on the microbiota to promote a favourable population, guarantee improved resilience of the fish in stressful environments and improve overall digestive functions and feed efficacy.
Aquaviance: The genesis of an aquaculture dedicated solution
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 prerequisites of technological constraints 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 effects of the product after extrusion and inside the digestive tract, the product is encapsulated via a special process.
1. In-vitro efficacy against pathogens
A Minimum Inhibitory Concentration (MIC)/Minimum Bactericidal Concentration (MBC) test was performed to assess the efficacy of the Aquaviance blend on the most impacting pathogens, to guarantee a vast operating range of action at constant concentrations. The trial was done by testing the Aquaviance blend on eight types of pathogenic bacteria, and challenged with a different blend of three strains of vibrio.
The results showed a constant minimum bactericidal concentration in-vitro located around 250μg/ml for the Aquaviance blend and a four-to-eight times higher efficacy when compared with the second essential oils blend, showing that all essential oils and their constituents do not have the same efficacy and knowing the correct ingredients at the right dosage is a prerequisite to guarantee the desired effect.
2. In-vivo trials
To validate the in-vivo efficacy of Aquaviance on digestive health and performances, several trials were performed on different species and various environments. The following results, from the Marine Science Institute, Jeju National University (Min-Gi K et al. 2014) shows details about the benefits of Aquaviance on olive flounder (Paralichthys olivaceus).
The nutritional trial was performed using three diets: A commercial diet as control and the same diet with 0.1 percent and 0.2 percent of Aquaviance. The fish (IBw: 27.4g) were fed for 75 days and zootechnical parameters were recorded, as well as apparent digestibility. The results showed improved growth, feed efficacy, protein digestion and protein efficiency ratio. Survival remained high, without significant differences between the groups.
Statistical differences appeared between control and Aquaviance at 0.1 percent for dry matter and protein apparent digestibility and at 0.2 percent regarding the FCR, and protein efficiency ratio. These results are in line with a better valorisation of the feed.
Even though the diet contains a high amount of fishmeal (46%), these effects can be explained by the positive impact of Aquaviance on the gut microflora and the overall digestive health, leading to a more efficient digestion and better growth.
University trials are an excellent way to validate in-vitro efficacy of feed additives, however, farm conditions are much more complex and prone to variations, challenging the mode of actions of additives. Aquaviance was designed taking in 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 six-month periods.
From August to February, fish (IBw: 79g) treated with 1.5kg/T of Aquaviance were 25 percent bigger than the control group and had FCR reduced by eight percent. 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 percent growth increase and a two percent reduction for FCR. Used in a full Litopenaeus vannamei cycle in Ecuadorian conditions, Aquaviance at 2kg/t gave better growth (+8%), survival (+7%) and lower FCR (-25%).
In both cases, beside the big differences of species and environment, the gain of biomass and reduction of feed cost provided substantial monetary gain for the farmers. Aquaviance proved itself many times to be an effective tool for fish and shrimp farmers, suitable for diverse environments and diverse species of aquaculture (Sadek S. et al, 2012 Le Than Hung et al. 2008, Calvez., 2018).
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.