ISSUE FOCUS FEED & ADDITIVE MAGAZINE August 2025 55 trials is a combination of specifically selected inactive yeasts containing Saccharomyces cerevisiae and Cyberlindnera jadinii strains and their derivatives. This combination helps promote a synergistic effect on the immune response through multi-receptor activation and resolution of inflammation without the risk of immune fatigue. It also helps maintain skin health by increasing skin mucus excretion, supporting antimicrobial activity, and tissue regeneration. This approach represents a shift from reactive treatment to proactive welfare maintenance through mucosal health support. Selected salmon had an initial body weight of 200250g and were maintained at 13±1°C in 33 parts per thousand (ppt) salinity conditions. Fish were fed a post-smolt diet mimicking commercial recipes that were formulated and tested as control or supplemented with the yeast supplement in quadruplicate. Salmon were reared for five weeks under ideal conditions then exposed to a first standard AGD-challenge followed, two weeks later, by a freshwater bath and a second standard AGD-challenge. The trial employed a gill scoring system to evaluate lesion development and severity. Results suggested that nutritional intervention significantly influenced both growth performance and gill tissue response to pathogen challenge. Fish receiving the functional diet showed 20% improvement in specific growth rate and 32% enhancement in feed conversion ratio (FCR) compared to controls (p<0.05 for both parameters; Figure 1A and B). Over the trial’s duration, the gill score progressively increased from light to moderate and advanced lesions. At the end of the trial, the proportion of advanced and heavy lesions was significantly reduced in the supplemented group (two-fold and six-fold respectively, p<0.01). Conversely, the proportion of fish showing only light lesions was significantly higher in the YCW-supplemented group (Figure 1C). A. SGR B. FCR * ** % % 1 0.5 0 +20% - 32% x 2 = x 3 x 6 3 2 1 0 Control YCW Control YCW 100 75 50 25 0 Control YCW Diet Lesion category Control Yeast Cell Wall Heavy Light Advanced Moderate C. Gill Score Proportions Correspondance Analysis p = 0.002 Figure 1. Effects of YCW supplementation on Atlantic salmon challenged with amoeba gill disease. A) Specific growth rate (SGR) improvement, B) Feed conversion ratio (FCR) enhancement, and C) Distribution of gill lesion severity categories at trial conclusion Statistical significance: * p<0.05, ** p<0.01
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