ISSUE FOCUS FEED & ADDITIVE MAGAZINE September 2024 59 (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
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