ISSUE FOCUS 54 FEED & ADDITIVE MAGAZINE August 2025 ROLE OF MUCOSAL HEALTH FOR FISH WELFARE: INSIGHTS FROM YEAST-BASED FEED TRIALS Dr. Camille Houdelet R&D Project Leader in Aquaculture Lallemand Animal Nutrition Mucosal health for fish welfare begins at the surface level. New research from Scotland and Canada demonstrates how gill and skin health serve as reliable indicators of overall fish vitality and adaptive capacity. Two breakthrough trials reveal that maintaining mucosal tissue integrity through targeted nutrition offers a welfare foundation approach, shifting aquaculture from reactive disease treatment to proactive health maintenance. In fish, mucosal surfaces are the body’s first line of defense against environmental challenges such as sudden variations in water quality and temperature, and exposure to pathogens and non-infectious harmful agents. These barriers are critical to keeping fish healthy and productive. Intensive farming often subjects fish to repeated stressors that compromise gut, skin and gill barriers. There are three major categories of insults that can compromise health and performance: Infectious and non-infectious agents such as bacteria, parasites, viruses, toxic algae, and plankton; environmental threats like water quality, heat stress, and rapid temperature changes; and management practices such as transfers, handling, treatments, and net-cleaning operations. Recent research from Lallemand Animal Nutrition has focused on understanding how maintaining mucosal tissue integrity can support salmon health when faced with common aquaculture pathogens. Two independent trials, conducted in Scotland and Canada, examined the relationship between mucosal surface health and fish performance, salmon in particular, when exposed to different pathogens. These studies provide insights into how nutritional interventions targeting mucosal surfaces may serve as a reliable strategy to support overall fish welfare and adaptive capacity. SUPPORTING GILL HEALTH IN AMOEBA-PRONE ENVIRONMENTS Amoeba gill disease (AGD) is caused by the marine ectoparasite Neoparamoeba perurans, which colonizes and induces gill damage, resulting in significant losses in the Atlantic salmon industry across major producing regions. Current solutions include freshwater or hydrogen peroxide bathing, which can be operationally and biologically challenging. A 10-week trial was performed in Scotland to test the potential contribution of a novel yeast-based functional ingredient for mitigating the incidence of AGD in Atlantic salmon under controlled conditions. Yeast cell wall (YCW) tested in the mentioned
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