Impact of Omega-3 Fatty Acids Nano-Formulation on Growth, Antioxidant Potential, Fillet Quality, Immunity, Autophagy-Related Genes and Aeromonas hydrophila Resistance in Nile Tilapia (Oreochromis niloticus)

Abstract

In modern aquaculture, enriching Nile tilapia’s diet with omega-3 poly-unsaturated fatty acids (PUFAs) not only plays an important role in its general health but also fortifies its fillet with omega-3-PUFAs. However, the major challenge affecting their delivery is their high instability due to oxidative deterioration. Thus, the prospective incorporation of omega-3-PUFAs into nanocarriers can enhance their stability and bioactivity. In this regard, the effect of reformulated omega-3-NPs was investigated on Nile tilapia’s performance, flesh antioxidant stability, immunity, and disease resistance. Four fish groups supplemented with omega-3-PUFAs-loaded nanoparticles (omega-3 NPs) at levels of 0, 1, 2, and 3 g/kg diet and at the end of feeding trial fish challenged with Aeromonas hydrophila. Fish performance (weight gain and feed conversion) was improved in groups supplemented with omega-3-NPs (2 and 3 g/kg diet). The deposition of omega-3-PUFAs in fish flesh elevated with increasing dietary omega-3-NPs. Simultaneously the oxidative markers (H2O2, MDA, and reactive oxygen species) in fish flesh were reduced, especially with higher omega-3-NPs. Post-challenge, downregulation of IL-1β, IL-6, IL-8, TNF-α, and caspase-1 were noticed after dietary supplementation of omega-3-NPs. Moreover, mRNA expression of autophagy-related genes was upregulated while the mTOR gene was downregulated with higher omega-3 NPs levels. Lower expression of A. hydrophila ahyI and ahyR genes were detected with omega-3 NPs supplementation. In conclusion, omega-3-NPs application can fortify tilapia flesh with omega-3-PUFAs and augment its performance, immunity, and disease resistance against Aeromonas hydrophila.

Exploring the Interactive Effects of Thymol and Thymoquinone: Moving towards an Enhanced Performance, Gross Margin, Immunity and Aeromonas sobria Resistance of Nile Tilapia (Oreochromis niloticus)

“…In the current study, fish fed a combination of Thy and ThQ displayed the highest expression levels of atg5 , atg12 , lc3-II and bclN-1 genes and the lowest downregulating level of mtoR expression. In agreement with our results, a previous study stated that natural feed supplements upregulated atg5 , atg12 , lc3-II and bclN-1 genes and downregulated the mtor gene in Nile tilapia post A. hydrophila challenge [ 8 ]; however, there are no studies investigating the effect of thymol and thymoquinone on autophagy-related genes in Nile tilapia.…”

“…The fish antioxidant defense system is greatly associated with their immune and health conditions. Situations of diseases lead to physiological changes associated with oxidative stress, which results from a disproportion in the generation of nitrogen species/reactive oxygen species (ROS) and antioxidant and immunological reactions [ 8 , 10 , 71 ]. The antioxidant enzymes are important regulators of the antioxidant defense system of fish through eliminating the excessive ROS and thus, maintaining the homeostasis of cells [ 4 ].…”

“…Autophagy is a mechanism, in which lysosomes used by the cells to destroy organelles and macromolecules are damaged. The innate immune response and autophagy might act through a combined signaling pathway [ 8 ]. To control the adaptive immunity, the immune system uses the destroyed products from the autophagy process [ 80 ].…”

“…One of the main problems in the fish industry in developing countries is the overuse of antimicrobial agents in aquaculture, which results in the emergence of resistant microorganisms and the presence of antimicrobial residues in the fish flesh [ 6 , 7 ]. Furthermore, fish raised in intensive fish cultures are exposed to short-term food deprivation and high stocking density in response to overproduction [ 8 ], which makes them susceptible to stress conditions that have harmful effects on their physiological functions, and immune defense leading to significant economic losses and high mortality rates [ 9 ]. Fish have developed numerous strategies to combat oxidative stress via generating antioxidants those can remove dangerous free radicals with a consequence of preventing diseases and mitigating cell damage [ 1 ].…”

“…such as Aeromonas hydrophila ( A. hydrophila ) and A. sobria [ 10 , 11 ] have several strategies to disrupt the immune systems of fish resulting in the spread of serious diseases. The pathogenicity of these pathogens is complicated and they depend on many virulence factors such as invasion, adhesion, biofilm formation, motility, resistance to phagocytosis and production of exotoxins such as hemolysin/aerolysin, proteases, lipases and cytolytic toxins [ 4 , 8 , 12 ]. A. sobria infection in fish is fatal resulting in ulcer formation, ascites and hemorrhagic septicemia.…”