Phytogenics comprise of a relatively infant department of feed additives that are gaining considerable interest within the aquaculture industry. A wide spectrum of phytogenics, particularly those containing terpene and saponin compounds, are increasingly supplemented in aquafeeds, due to their antimicrobial, immunomodulatory, antioxidant, anti-inflammatory, and growth promoting properties.
Aqua Technical Sales Manager
Anpario plc
OVERVIEW OF GLOBAL AQUACULTURE TRENDS
Aquaculture is continuously expanding as a consequence of the demand for healthy and nutritious food; which, along with the global saturation of wild fishery production, has encouraged considerable growth of the sector. It is currently the fastest growing food producing sector in the world, growing at a rate between 5.6 to 7.8% per year. The Food and Agriculture Organization (FAO) estimates the global yield of wild fisheries to achieve 91 million tonnes in 2030, barely 1% higher than that in 2016. Contrastingly, the predicted annual production for aquaculture is 109 million tonnes by 2030, approximately 37% higher than that in 2016.
Although aquaculture has accelerated rapidly, the diversification and intensification of its practices have been implemented to sustain high production levels; which, correspondingly, necessitates substantial quantities of high-quality, affordable, and sustainable feed ingredients to achieve maximum production performance. Recently, interests have shifted towards using innovative feed additives, such as phytogenics, to enhance the value of aquafeeds and improve the health and growth performance of aquaculture species.
WHAT ARE PHYTOGENIC FEED ADDITIVES?
Phytogenics, also known as phytochemicals, photobiotics, or botanicals, are natural bioactive compounds that are derived from herbs, spices, or other plants and incorporated into feedstuff with the aim of improving animal health and growth performance. Essential oils constitute a concentrated form of phytogenics, comprising mainly of the bioactive compounds of the plant, such as terpenes and polyphenols. The dietary supplementation of essential oils, such as oregano essential oil (OEO), demonstrates a simple, yet proficient approach to enhance the productivity of aquaculture species.
COMPLEX MODE OF ACTION OF OREGANO ESSENTIAL OIL
OEO, as an aquafeed additive, can provide an unwavering number of benefits, with a well-documented efficacy in improving the health status and growth performance across numerous aquaculture species including, but not limited to, Nile tilapia (Oreochromis niloticus), Pacific whiteleg shrimp (Litopeneaus vannamei), Atlantic salmon (Salmo salar), common carp (Cyprinus carpio), and rainbow trout (Oncorhynchus mykiss). The Orego-Stim range from Anpario comprises of a unique source of 100% natural OEO which contains over 100 active compounds, with the primary highly-functional compounds being carvacrol, thymol, p-cymene, β-caryophyllene, γ-terpinene, and linalool. These main constituents of OEO work in synergy to provide a complex mode of action, including antioxidant, antimicrobial, immunomodulatory, growth promoting, and anti-inflammatory functions.
EFFECTIVELY MANAGING AQUACULTURE DISEASES WITH PHYTOGENICS
Aquaculture is plagued by a plethora of bacterial pathogens, and the rearing of fish and shrimp at high population densities in aquaculture facilities makes them particularly susceptible to disease outbreaks, causing massive mortalities. In the last two decades, the aquaculture sector has suffered major economic tragedies due to infectious diseases, estimated at more than $6 billion per year.
However, phytogenic feed additives are one of the most significant approaches for improving the immunity of aquaculture species. Immunity plays a crucial role in protecting the host from disease, it aids in preventing infections and reduces the severity of diseases. Numerous studies demonstrate the beneficial effects of OEO supplementation on the health status of aquatic species, including an improved haematological profile by increased counts of red blood cells, white blood cells, haemoglobin, and differential immunoglobulins. OEO has also shown promising results in improving innate and adaptive immune responses in fish, mainly through improving lysozyme, protease, and complement system activities, and increasing the production of phagocytes, cytokines, plasma B cells, and T cells including T helper cells and cytotoxic T cells.
The effective control of disease has recently become increasingly difficult in aquaculture due to the phenomenon of antibiotic resistance. Antimicrobial resistance (AMR) is a global public health problem which has been identified as a significant health threat by the World Health Organisation. The expeditious rise in AMR is attributed to the inappropriate and/or overuse of antibiotics. Antibiotics are the main solution for managing bacterial diseases in aquaculture; however, they have been misused and evidently, exploited. Although, just like in the public health sector, AMR has become a major challenge in aquaculture. Therefore, alternative antimicrobial agents, including those of natural origin such as phytogenics, are being sought for the development of natural growth promoters (NGPs).
OEO exhibits a broad antimicrobial action which is attributable to the lipophilic nature of its phenolic compounds. The antibacterial activity of carvacrol and thymol is dependent on causing a division in the cell homeostasis by increasing the fluidity and permeability of the cell membrane, thus reducing the membrane potential. The leakage of vital intracellular constituents and metabolic imbalance are also associated with the structural and functional alterations of bacterial cell membranes caused by these compounds. Additionally, carvacrol has adenosine triphosphatase inhibiting activity and functions as a proton exchanger that decreases the gradient through the bacterial cell membrane. This results in the falling of the membrane proton motive force and depletion of adenosine triphosphate, ultimately causing cell death.
Supplementation of OEO in fish and shrimp diets has demonstrated a high level of efficacy in preventing and controlling bacterial diseases caused by species of Flavobacterium, Aeromonas, Vibrio, Francisella, Salmonella, Pseudomonas, and Streptococcus. Anpario’s Orego-Stim Forte is a phytogenic product specifically designed for use within aquaculture, comprising of a unique source of 100% natural OEO and Quillaja saponaria (QS) extract which work in synergy to provide a complex mode of action.
The University of Plymouth (UK) conducted a trial to determine the in vitro antagonism of Orego-Stim Forte against multiple species of pathogenic bacteria affecting aquaculture species. The results in figure 1 demonstrate the inhibitory efficacy of Orego-Stim Forte against all five pathogens when included at 2500ppm (2.5kg/t feed). Such findings highlight the potential for natural solutions, such as Orego-Stim Forte, to support fish and shrimp health, safeguard antibiotics, and protect against AMR.
As well as proven efficacy in vitro, Orego-Stim Forte trials have demonstrated success in the production of shrimp when challenged with a disease. Vibrio parahaemolyticus is ubiquitous to many aquaculture environments and can cause diseases such as white faeces syndrome (WFS) and acute hepatopancreatic necrotic disease (AHPND) in L. vannamei, resulting in significant losses for the shrimp farming industry.
An independent trial, conducted by Nong Lam University, in Vietnam, used 20 tanks containing 80 shrimp per tank with four replicates. At the end of an 8-week feeding period, 20 shrimp from each treatment were randomly selected and challenged with V. parahaemolyticus. Mortality rates were recorded for two weeks and at the end of the experiment total haematocyte count (THC), phenoloxidase activity and total Vibrio count were determined. In figure 2, the mortality of L. vannamei challenged with V. parahaemolyticus showed a decreasing tendency with increasing administration doses of Orego-Stim Forte, thus supporting the antibacterial activity of OEO and QS. A significant difference was observed between the control and Orego-Stim Forte diet at 3.5kg/t (D3), which demonstrates the efficacy of Orego-Stim Forte for in vivo scenarios. THCs tended to be higher in the groups supplemented with Orego-Stim Forte, thus indicating more efficient elimination of bacteria from the haemolymph of shrimp fed Orego-Stim Forte. Phenoloxidase, an enzyme that catalyses the shrimp’s natural antioxidative system, tended to be higher in the groups previously fed Orego-Stim Forte. Additionally, this trial resulted in a return-on-investment (ROI) ratio calculated at >8:1 to a shrimp producer when using Orego-Stim Forte at 3.5kg per tonne of feed.
THE GROWTH PERFORMANCE ENHANCING EFFECTS OF PHYTOGENIC FEED ADDITIVES
In fish, several studies have examined the beneficial effects of supplementing OEO and QS to improve growth rate, mainly via improving the intestinal histomorphometry and increasing activities of digestive enzymes. The dietary inclusion of OEO and QS across a multitude of fish and shrimp species has demonstrated efficacy in increasing villus size and quantity, thus improving intestinal absorption surface area and nutrient utilisation. The improved intestinal histomorphometry may be attributable to antimicrobial activity of OEO and QS, causing a reduction of harmful bacteria and consequently, reducing mucosal damage. The activities of endogenous digestive enzymes are often used as a benchmark for determining the digestive capacity and nutritional status of fish. Supplementing OEO and QS in O. niloticus and C. carpio diets have successfully demonstrated a significant improvement in the stimulation of amylase, lipase, and protease activity, which resulted in improved growth indices for both species.
Ballan wrasse (Labrus bergylta), as cleaner fish, are viewed as a sustainable and effective management tool for the biological control of sea lice in salmon farming. A study using 1,350, split into nine tanks, was conducted over an 83-day period by an independent research provider, Otter Ferry Seafish, located in Scotland, UK. L. bergylta were fed one of three dietary groups in triplicate; Control, T1 (Orego-Stim Forte at 1kg/t), and T2 (Orego-Stim Forte at 3.5kg/t). This trial concluded that dietary Orego-Stim Forte supplementation, at both concentrations, improved the specific growth rate (SGR) and feed conversion ratio (FCR) of L. bergylta (figure 3). The greatest SGR and FCR improvements were seen in the diet containing 3.5kg/t of Orego-Stim Forte, which is 13.2% and 10.7%, respectively, more advantageous compared to the control.
CONCLUDING REMARKS
With the significant growth trajectory of the aquaculture sector coupled with the ballooning human population, it is essential, now more than ever, to provide aquaculture producers with highly effective and sustainable solutions. Phytogenic feed additives have demonstrated their potential for improving the health and growth performance of aquaculture species whilst supporting antibiotic free production in the fight against antimicrobial resistance. The antioxidant, anti-inflammatory, immunomodulatory, antimicrobial, and growth promoting natural properties of Anpario’s Orego-Stim range, makes them highly-effective, yet sustainable solutions.
References available on request.
About Gerred Fuchs
Gerred Fuchs joined Anpario at the beginning of this year as the Aqua Technical Sales Manager. As part of his role, Fuchs supports product development and strengthens technical support across Brazil and Egypt, in response to Anpario’s deepening focus within the aquaculture sector. Prior to his current role at Anpario, Fuchs completed a Master of Research focussing on aquaculture feed additives at the University of Portsmouth, following a BSc in Aquaculture and Fishery Management from University Centre Sparholt. Fuchs’s previous industrial experiences include Aquatic Sales, Aquatic Technician for salmonid trials, and researching novel feed ingredients and additives to improve the health, diet utilisation, growth performance, and production sustainability of various aquaculture species.
