As aquaculture increasingly adopts functional feed additives to bolster resilience, interest is growing in strategies that enhance the tolerance of farmed shrimp to environmental stressors. The effect of a brewer’s yeast (Saccharomyces cerevisiae) additive (Biolex® MB40, Leiber GmbH) on growth performance and stress tolerance in whiteleg shrimp (Litopenaeus vannamei) was evaluated using a thermal-challenge model.
Juvenile shrimp (3.2 ± 0.2 g) were reared for 28 days in a semi-recirculating aquaculture system (salinity 30 ppt; 12.5% daily water exchange). Two isoproteic and isolipidic diets (crude protein 43.8 ± 0.8%; lipid 7.5 ± 0.1%) were evaluated: a control diet without YCW supplementation (0-YCW) and a diet supplemented with 0.2% YCW (0.2-YCW). Each treatment was assigned to three replicate 16-L tanks containing six shrimp per tank. Water temperature was maintained at 26 °C from Days 0-14, then rapidly reduced by 4 °C per hour on Day 14 until reaching 16 °C, where it was held until Day 28.
Data were statistically analysed at the pre-challenge (Day 14; 26 °C) and post-challenge (Day 28; 16 °C) phases using a two-sample t-test (Real Statistics® package, Microsoft® Excel). During the pre-challenge phase, survival was 100% across both treatments.
However, shrimp fed the 0.2% YCW diet showed significantly improved feed conversion ratio (FCR; P = 0.042; Fig. 1) and protein efficiency ratio (PER; P = 0.027; Fig. 2) compared with the 0-YCW group.
In the post-challenge phase (Days 14-28), following the rapid temperature drop, shrimp appetite declined, and the feeding rate was reduced from 3.6% of body weight per day in the first phase (Days 1-14) to 2.3% in the second phase. No significant differences (P > 0.05) were detected between treatments in growth performance, FCR, PER, or survival (with only one mortality recorded).
Collectively, the data indicate that dietary YCW at 0.2% can enhance FCR and PER in L. vannamei, but such benefits were not observed under severe cold stress (16 °C). Ongoing analyses of distal intestine, gill, and hepatopancreas (histology, gene expression, and 16S rRNA gene metabarcoding) is being conducted to determine whether the YCW confers immunological, mucosal, or microbiome-level protection during cold challenge.