Moving towards more sustainable aquaculture practices: a meta‐analysis on the potential of plant‐enriched diets to improve fish growth, immunity and disease resistance

Abstract

Aquatic animal diseases are one of the major limiting factors in aquaculture development, with disease emergence forecast to increase with global change. However, in order to treat increasing diseases in a context of global emergence of antimicrobial resistance and strengthening regulations on antimicrobial use, sustainable alternatives are urgently needed. The use of plant supplements to increase fish immunity and disease resistance has gained much popularity within the last decades. The use of functional supplements, such as plants, can also improve growth and feed assimilation, contributing to a better optimization of aquaculture resources (e.g. fish meal inclusion). We conducted a systematic review and metaanalysis in order to identify the research gaps in the use of plant-enriched diets in fish aquaculture and estimate, for the first time, the overall efficacy of plant-enriched diets on fish growth, immunity and disease resistance as well as the effect of intrinsic parameters (fish trophic level, type of plant material, dosage, treatment duration and pathogen species) on the treatment efficacy. We found that plant-enriched diets significantly enhanced growth, immunity and disease survival of treated fish, regardless of the fish trophic level, treatment duration and type of material used. We also show that plant supplements are a versatile alternative that can benefit different aquaculture sectors (from small-scale fish farmers to intensive productions). Finally, we observed that studies need to improve the information reported about the plant material used (e.g. origin, identification, chemical composition), in order to allow the comparison of different experiments and improve their repeatability.

Oregano (Origanum vulgare) Extract Enhances Zebrafish (Danio rerio) Growth Performance, Serum and Mucus Innate Immune Responses and Resistance against Aeromonas hydrophila Challenge

“…In fish, the primary lines of non-specific defenses are the skin and mucus supported by several soluble factors, such as activities of complements and lysozymes. The use of medicinal plants in aquaculture has been widely studied, implying their great potential to enhance growth, immunity and resistance against various experimental bacterial infections [ 1 , 2 , 3 , 4 , 5 ]. This suggests the great potential of natural compounds for substituting synthetic drugs and antibiotics in aquaculture.…”

“…In particular, the remarkable role of medicinal plants has been recently discovered in aquaculture; in fact, they can stimulate the immune system, conferring early activation of non-specific defense mechanisms of fish. Medicinal plants archive their positive effects due to their contents such as polysaccharides, tannins, pigments, steroids, terpenoids, flavonoids, phenolic compounds, organic acids, alkaloids, glycosides and essential volatile oils [ 3 , 6 , 7 , 8 , 9 ]. Certain medicinal plants (herbs) possessing well-known immunostimulant effects have been used experimentally as well as clinically to treat various fish diseases and to control infections, for example, the septicemia caused by the bacteria Aeromonas hydrophila .…”

“…A. hydrophila is widespread and economically relevant and this bacterium has been associated with disease in zebrafish ( Danio rerio ), salmonids ( Salmonidae ), carp ( Cyprinus carpio ), eels ( Anguilliformes ssp. ), milkfish, ( Chanos chanos ), channel catfish ( Ictalurus punctatus ), tilapia ( Oreochromis niloticus ) and ayu ( Plecoglossus altivelis ), and it can also be an opportunist in stress-related diseases [ 3 ]. In tilapia ( Oreochromis mossambicus ), effects on the non-specific humoral (lysozyme, antiprotease and complement) and cellular (myeloperoxidase content, production of reactive oxygen and nitrogen species) responses and disease resistance against A. hydrophila were evident.…”

A Multi-Biomarker Approach in European Sea Bass Exposed to Dynamic Temperature Changes under Dietary Supplementation with Origanum vulgare Essential Oil

“…Whether medicinal plants can be administered to fish in several ways (e.g., intramuscular and intraperitoneal injection, immersion, or baths), oral administration seems to be the most suitable for aquaculture. Plants can be administered as a whole plant or parts (leaf, root, seed, fruit) and can either be used fresh or as powder, plant-extract, or essential oils (EO) [ 17 , 18 ]. Recently, much attention has been given to EO-enriched diets in order to preserve the fish healthiness and to minimize the farming cost, as well as to improve the fillet nutritional quality [ 16 ].…”

“…Adequate dosing is crucial to obtain the desired effects, since most of the plant bioactive molecules may result toxic or antinutritional at high levels. Treatment duration is another important parameter, since it directly affects the treatment effectiveness [ 17 , 18 ].…”