Abstract
In the present study, a yeast strain Saccharomyces cerevisia var. elipsoidous , acting as probiotic, was administered to rainbow trout ( Oncorhynchus mykiss Walbaum, 1792) fry during a period of 21 days and the effects of the yeast on improvement of growth and resistance against environmental stress were evaluated with respect to fish fed on yeast free feed (control group). The control treatment consisted of a standard commercial diet, and the treatments consisted of the control diet supplemented with 0, 1, 5 and 10% yeast (w/w). The results demonstrate the beneficial effects of probiotics on the characteristics of rainbow trout, as the Specific Growth Ratio (SGR), body weight gain (%BWG) and protein conversion ratio (PER) in 5% yeast-fed fish were significantly (P<0.05) enhanced by probiotic administration. On the contrary, no effect on the fry growth performance, mortality, condition factor (CF), food conversion ratio (FCR) and histological assessment was shown. A significant (P<0.05) increase in lipid content of the carcass was detected in diets with probiotic compareD to 0% and the control treatments. Ash and protein contents of the carcass increased and decreased with an increase in yeast amount, respectively. Challenge with different levels of salinity (10 and 15 ppt) after 24 h revealed 100% survival in treatments containing yeast as probiotic, and difference with control group was significant (p<0.05) indicating that S. cerevisia could enhance the resistance against salinity stress. Addition of yeast in concentration of 5% to the diet is recommended during the early period of rainbow trout fry farming to achieve the best results on growth performance and feed efficiency. Keywords: Saccharomyces cerevisia var. elipsoidous , Oncorhynchus mykiss , probiotic, survival and growth rate, carcass quality African Journal of Biotechnology , Vol. 13(10), pp. 1160-1168, 5 March, 2014
Highlights
Today, increase in demand for fish products means using intensive methods for more production, accompanied with an increase in infectious agents
The results demonstrate the beneficial effects of probiotics on the characteristics of rainbow trout, as the Specific Growth Ratio (SGR), body weight gain (%BWG) and protein conversion ratio (PER) in 5% yeast-fed fish were significantly (P
Fry of O. mykiss fed with different levels of S. cerevisiae had a higher growth rate than those fed with normal artificial food and artificial diet covered by fish oil at the first week (C and D0)
Summary
Increase in demand for fish products means using intensive methods for more production, accompanied with an increase in infectious agents This rearing condition can be a source of stress for fish, making them susceptible to disease and triggering high mortality. Probiotics, which are micro-organisms or their products with health benefit to the host, have found use in aquaculture for improving the health of their host and increasing growth rate. The effects of probiotics on survival and growth rate of fish larvae and crustacea such as digestibility coefficients of nutrients, decreasing food conversion ratio and increase tolerance to stress have been studied (Rengpipat et al, 1998; Ali, 2000; Heizhao et al, 2004; Himabindu et al, 2004; Taoka et al, 2006a). It has been shown that the use of probiotics can increase the amount of given food necessary for animal optimal growth, by which the expense of fish farming might be reduced (Lara-Flores et al, 2003)
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