Medium-chain fatty acids as feed supplements on immune enhancement in sustainable aquaculture

In terms of chemical structure, medium-chain fatty acids (MCFAs) have carbon chain lengths of 6–12 atoms. These fatty acids can be found in high amounts in natural sources such as coconut oil, palm kernel oil, and dairy products. Regarding the types of medium-chain fatty acids that received more attention, caproic acid (C6), caprylic acid (C8), capric acid (C10), and lauric acid (C12) can be mentioned. The metabolism of these acids in the bodies of aquatic animals is fast, and they have rapid absorption in the intestine. They reach the liver directly via the mesenteric vessels and the portal vein. In the liver, digestion processes like energy production occur. Studies conducted on aquatic animals showed beneficial effects of these fatty acids on growth performance, feed efficiency, and modulation of gut microbiota composition. Also, results confirm the beneficial effects of these functional feed additives on the antioxidant defence system and immune response in different aquatic species. The present review paper deals with the application and effects of MCFAs and their salts in aquaculture. The focus of this review was on their effects on growth performance, immunobiochemical responses, immune gene expression, and activities of antioxidant and digestive enzymes. Possible mechanisms of action of these fatty acids on the mentioned parameters and their effects on the improvement of resistance against pathogens were reviewed in detail. The aim of this paper is to show the potential of MCFAs for the health and production of aquatic species. In addition to the above cases, research gaps and the areas that need further studies are described in this review.