The utilization and mode of action of organic acids in the feeds of cultured aquatic animals

Abstract

The use of antibiotics in the feeds of cultured aquatic animals to mitigate infectious diseases or to boost growth performance is commonly practised. In recent years, the prophylactic use of antibiotics has been criticized which eventually led to their ban in animal production by many countries. In view of the current restrictions on antibiotic use, there is a critical need to evaluate alternatives. One potential substitute for antibiotic growth promoters in aquafeeds is organic acids and/or their respective salts. The use of dietary organic acids in the culture of aquatic animals has been the focus of much research and commercial interest recently. This review provides a comprehensive compilation of the current knowledge on the use of organic acids in aquafeeds, with emphasis on its impacts on growth, nutrient utilization, mineral availability, gut microbiota and disease resistance. Many studies have reported that some organic acids can significantly enhance the growth performance and health status of fish. Contradictory results have also been reported, which seems to depend on the aquatic animal species, type and concentrations of organic acids and the culture conditions used. Recent research indicating the beneficial impact of dietary organic acids on shrimp growth and health is highlighted. Possible mechanisms of action of these functional feed additives are discussed. Strategies for enhancing the effectiveness of dietary organic acids are given. This review aims to contribute to the sustainability of global aquaculture production by providing a viable alternative to harmful antibiotics, thereby meeting the growing consumer demand for antibiotic-free seafood products.

Citric acid as a feed additive in pacu Piaractus mesopotamicus (Holmberg, 1887) diets

“…fed diets with 2.0% potassium diformate or a blend of 1.0, 2.0 and 3.0% organic acids (Ng et al., ), and rainbow trout Oncorhynchus mykiss fed diets containing 0.0, 4.0, 8.0 and 16.0% citric acid showed no differences in their growth performances (Vielma, Ruohonen, & Lall, ). The contradictory results among studies could be related to the different species, as well as levels and types of organic acid added to the diets (Ng & Koh, ).…”

Beneficial roles of feed additives as immunostimulants in aquaculture: a review

“…Organic acids are short‐chain fatty acids, volatile fatty acids or weak carboxylic acids, such as formic, citric, benzoic and lactic acid (Bai et al . ; Elala & Ragaa ; Ng & Koh ). Organic acids have been used for decades as food preservatives in livestock feeds due to their antimicrobial properties, as well as their ability to enhance growth, nutrient utilization and disease resistance of aquatic animals (Ng & Koh ).…”

“…). The major impacts of these dietary organic acids in fish and shrimp are summarized by Ng and Koh (). Despite the discrepancies among the published data, it appears that organic acids and/or their salts have good potential as dietary supplements to improve growth performance, feed utilization, nutrient digestibility, disease resistance as well as the alteration of the gut microbiota populations in several aquatic animal species (Lim et al .…”

Dietary short-chain organic acids enhanced resistance to bacterial infection and hepatopancreatic structural integrity of the giant freshwater prawn, Macrobrachium rosenbergii

“…The beneficial effects of dietary organic acids to the gastrointestinal tract of aquatic animals can include reducing potentially harmful bacteria in favor of more beneficial bacteria (e.g., lactic acid bacteria); however, the effectiveness of organic acids to disease resistance can be highly dependent on the host species and the type of organic acid used, often leading to contrasting findings (reviewed by Ng and Koh 2016). It is known that bacterial pathogens such as Vibrio spp.…”

“…Moreover, when injected, V. harveyi was shown to be highly virulent to M. rosenbergii juveniles, which was suggested to become an increasing disease problem to freshwater hosts (Siripornadulsil et al 2014). Apart from anti-bacterial properties, organic acids including SCFA can have a beneficial impact on farmed aquatic animals by enhancing nutrient availability, feed palatability, digestive enzyme activity as well as gut morphology (as reviewed in Ng and Koh, 2016). Dietary organic acids have also been reported to enhance the non-specific immune response of shrimp and have shown substantial promise in the control of vibriosis (Su et al 2014;Romano et al 2015;Ng et al 2015).…”