Feed Ingredients, Environmental Factors and Fish Mucosal Health

Dear Colleagues,

Aquaculture sustainability relies on better reproductive performance and quality, superior disease resistance, and improved feeding regimes and feed conversion. Breeding selection programs, implementation of circular economy and zero-waste perspectives, as well as constant innovation in feed formulation and rearing technologies have been envisaged as the best strategies to achieve the sustainability of this industry.

Environmental conditions control and monitoring technologies, as well as well-balanced feed are essential for fish growth, development and wellbeing. The incorporation of fishmeal (FM) and fish oil (FO), the golden-standard nutritional sources for marine fish species, has been reshaped according to new trends toward greener or land-based aquafeeds. The total replacement of FM and FO by alternative raw materials has been shown to hamper fish growth. More modest approaches such as deficiency in amino acids or minerals and the presence of antinutritional factors, among other factors, demonstrated as fish physiology and immunocompetence at the digestive system have been impacted. While physico-chemical and/or enzymatic reactions have proven to be partially successful strategies to overcome these limitations, the identification and use of functional additives to boost mucosal immunity was another complementary or parallel development. Currently, innovative, integrated and sustainable rearing practices are being developed. Recirculation aquaculture systems, biofloc and integrated multi-trophic aquaculture are paramount approaches to decrease water consumption and nutrient recycling while maintaining good fish growth, wellbeing and reducing disease outbreaks. The ways in which feed ingredients and water quality control determine the status of the immune system in farmed organisms was always a cornerstone to warrant efficient production. Among the different tissues with immunocompetence, the gut-associated lymphoid tissue (GALT), acting as a physical, chemical and biological barrier for animal protection, is particularly relevant in the interconnection between the triad fish nutrition, environmental conditions and immunity. Thus, monitoring and understanding how GALT status is affected by nutrition and abiotic factors (temperature, oxygen, nitrogenous compounds, etc.) is required to achieve good growth and wellbeing in farmed fish.

While a greater understanding of how fish nutrition and environmental conditions affect general fish immune response, deciphering how this factors and new threats (e.g., climate change and pollution) might particularly impact mucosal health at cellular and molecular levels is vital. Furthermore, unveiling whether exposure during early development may boost the immune system (and the related mechanisms) may allow for the expansion of the circular economy in Western aquaculture.

Considering the success of our previous Special Issue, we are pleased to launch “Feed Ingredients, Environmental Factors and Fish Mucosal Health”. This Special Issue aims to present and compile the recent insights on how feed ingredients (macro- and micronutrients, but also functional additives), rearing practices and environmental factors positively or negatively affect fish growth and immunity, particularly the gut-associated lymphoid tissue, at cellular and/or molecular levels. Original research articles and reviews with fundamental or applied perspectives on how feed ingredients and environmental factors impact fish health, combining classical and innovative approaches, are welcome.

Dr. Ignacio Fernández
Dr. Patrícia Díaz-Rosales
Guest Editors

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