Nutritional immunity of fish intestines: important insights for sustainable aquaculture

Abstract

Intensive culture systems are usually employed to increase the production, but we suspect that, in such systems, fish suffer infection and stress, which weakens their health. However, such systems may fail due to lack of resources or difficulty in controlling the rearing conditions' optimization. When intensive culture systems fail, aquatic animals gradually stop feeding. Accordingly, their physiological status deteriorates, and their immunity is suppressed. Through some strategies, it is possible to protect fish from disease by providing balanced food that maintain intestinal health and improve digestion, thereby increasing immunity. Protecting the health of the intestinal barriers is the primary guarantee of fish health. The local immunity of the intestine is associated with the innate and adaptive immunity of the fish's entire body. Thus, it is necessary to understand the interaction between the gut microbiota and the general immune system, as well as the most important reasons that can increase or suppress intestinal immunity. Many studies have confirmed that balanced diets containing basic nutritional requirements are the primary factor for maintaining intestinal health in aquatic animals. Another strategy for improving the intestine's local immunity is to use some non-nutritional food additives that increase the activity of beneficial bacteria and the secretion of digestive enzymes and decrease the harmful bacteria. This review article aimed to clarify the relationship between a balanced aquafeed and the intestinal health of aquatic animals by discussing the findings of related studies. Awareness of this correlation between diet and intestinal health is expected to aid the aquaculture industry to develop proper nutritional strategies that ensure the protection of fish health.

Marine-Derived Chitosan Nanoparticles Improved the Intestinal Histo-Morphometrical Features in Association with the Health and Immune Response of Grey Mullet (Liza ramada)

“…The measurement of intestinal histomorphometrical features is a vital tool for evaluating the effect of dietary supplements on the intestinal absorption capacity and the neighboring intestinal immunity, as well as its relationship to the general immune system in the fish body [6,29]. The main findings of the current investigation are the enhancement of the intestinal morphometrical and histological features in L. ramada fed chitosan nanoparticles.…”

“…Moreover, fish are expected to suffer from malnutrition and stressful conditions, which induce inflammation in their intestinal health and deteriorate their intestinal immunity [5]. The impairment of their local intestinal immunity is correlated with their general immune response and their ability to resist fish infectious diseases [6]. Traditionally, antibiotics are used to relieve the inflammatory features caused by stress and malnutrition [7].…”

“…The microbial diversity in the fish's gastrointestinal tract (GIT) strongly participates in regulating intestinal immunity depending on the ratio between the beneficial and pathogenic microorganisms and the composition of the aquafeed nutrients [14]. More specifically, the beneficial bacteria secrete digestive enzymes to digest the nutrients and facilitate their absorption through the intestines of fish, enhancing the feed efficiency and the growth rate [6].…”

The Inclusion of the Microalga Scenedesmus sp. in Diets for Rainbow Trout, Onchorhynchus mykiss, Juveniles

“…Plant protein meals, such as soybean, rapeseed, and corn/wheat gluten meals, have been used successfully in several studies as ingredients for fish feeds [10][11][12][13][14]. Currently, commercial feeds contain blends of plant and fish proteins and oils [2,4].…”

“…However, a critical shortcoming of the crop-plant derived protein sources commonly used in aquafeeds is their deficiency in some essential amino acids, such as lysine, methionine, and tryptophan. In addition, plant protein sources contain a wide range of antinutritional factors; hence, high inclusion level of these ingredients can induce negative effects on growth performance [12][13][14][15][16]. As a result, protein sources of plant origin do not represent the ultimate alternative, although their fermentation under controlled conditions may improve their nutritional quality [16].…”