Abstract

This study evaluated the effects of two types of probiotics, a mix of two bacteria and one yeast, on growth performance and intestinal enzyme activity in Nile tilapia. Three diets were formulated containing the optimum protein level (40%) for tilapia fry: one was supplemented at 0.1% with a bacterial mixture containingStreptococcus faecium and Lactobacillus acidophilus; a second was supplemented at 0.1% with the yeast Saccharomyces cerevisiae; and a third, was complemented with a control diet without supplements. Two additional diets were formulated to contain 27% protein to serve as a stress factor. They were supplemented at 0.1% with either the bacterial probiotic mix or the yeast. The diets were fed for 9 weeks to tilapia fry housed in 20-L tanks at two densities: a high density of 20 fry per tank as a stress factor; and a low density of 10 fry per tank. Every week an organism was selected from each tank for the enzymatic analyses of unicellular protein, alkaline phosphatase, disaccharidases and peptidase. Results indicate that the fry fed with diets containing probiotic supplement exhibited greater growth rate than those fed with control diet. Of the four probiotic treatments, the 40% protein diet supplemented with yeast produced the best growth performance and feeding efficiency. This was attributed to an increase in the alkaline phosphatase activity, suggesting that yeast is an appropriate growth-stimulating additive in tilapia cultivation.

Key words: Probiotic, Nile tilapia, enzymatic activity, streptococcus,Lactobacillus, Saccharomyces.