Live Yeast (Saccharomyces cerevisiae var. boulardii) Supplementation in a European Sea Bass (Dicentrarchus labrax) Diet: Effects on the Growth and Immune Response Parameters

The present study aimed to evaluate the effects on the health conditions of European sea bass of the dietary inclusion of the live yeasts, Saccharomyces cerevisiae var. boulardii (LSB, CNCM I-1079 strain) administered at increasing concentrations (0, 100 and 300 mg Kg-1 of feed, named as LSB 0, 100, 300) for 90 days. The intestinal cytokine expression, non-specific immune response parameters, antibacterial activities of sera, skin and intestinal mucus and peroxidase activity were measured as fish welfare parameters, together with the growth parameters. The LSB did not impaired neither growth parameters nor morphometric indexes. LSB down-regulates interleukin-1? transcription in the distal gut of fish treated with 5.4 x 105 CFU g-1 (LSB100) for 21 days. Interleukin-6 mRNA level decreased significantly in the proximal gut at both doses of yeast, after 21 days of feeding; the gene expression of interleukin-6 was significantly lower in sea bass fed 10.81 x 105 CFU g-1 (LSB300) probiotic. The levels of TNF-? mRNA were not influenced by probiotic supplementation. Data collected in the present study suggests that LSB-supplemented diet acts on the sea bass gut immune system by modulating the expression of key inflammatory genes. Increases, although not significant, in the haematological and immunological parameters, more evident for respiratory burst and plasma lysozyme, were also recorded, suggesting that yeast dietary supplementation exerted a low immunostimulant activity.