The effects of dietary inactive brewer's yeast Saccharomyces cerevisiae var. ellipsoideus on the growth, physiological responses and gut microbiota of juvenile beluga (Huso huso)

A study was conducted to assess the effects of dietary commercial inactive brewer's yeast Saccharomyces cerevisiae var. ellipsoideus on the growth performance, survival rate, haematology, serum biochemical parameters and the intestinal microbiota of juvenile beluga sturgeon (Huso huso). Beluga juveniles (11.44 +/- 0.56 g) were randomly allocated into 9 oval tanks (350 L) at a density of 35 fish per tank and triplicate groups were fed either a basal control diet (0% yeast) or the basal diet supplemented with yeast (at 1 or 2%). After 6 weeks of feeding on the experimental diets, growth factors (final weight, specific growth rate (SGR) and feed conversion ratio (FCR)), survival rate, haematological parameters and serum metabolic products (cholesterol, glucose and total protein) were measured. Additionally, autochthonous culturable haeterotrophic bacteria and lactic acid bacteria (LAB) levels were determined by culture based methods. The results indicate that dietary supplementation of 2% S. cerevisiae var. ellipsoideus significantly improved final weight, weight gain, SGR and FCR compared to the control treatment (P<0.05). However survival rate, haematological parameters and serum biochemical parameters were not significantly affected by dietary yeast (P>0.05). Although the total autochthonous intestinal heterotrophic bacterial counts were not affected by dietary treatment (P>0.05), autochthonous LAB levels were significantly elevated in fish fed 2% dietary yeast (P<0.05). These results indicate that inactive S. cerevisiae var. ellipsoideus improves growth performance and modulates intestinal microbiota of beluga sturgeon without detrimentally impacting the basic haematological parameters assessed. Thus, we suggest that low level brewer's yeast may be used as a growth promoter for juvenile beluga sturgeon. (C) 2011 Elsevier B.V. All rights reserved.