The purpose of this study was to evaluate the effect of dietary administration of the live
yeast Saccaromyces castelli in Oreochromis niloticus as immunostimulant, growth promoter and
increase fish resistance to the bacterial diseases. Saccaromyces castelli was isolated from intestine
of black carp (Mylopharyngodon piceus). One hundred and thirty five apparently healthy O.
niloticus (20 ± 3 g average body weight) were assigned randomly to three groups; each group in
three replicates (15 fish per each replica). Commercial basal diet (crude protein 30%) was crushed,
and then divided into three parts. The first part was basal diet mixed with sterile saline as a control
(J{). The second (T2) and third (T3) parts were basal diet mixed with (5 and 10 g of live yeast / kg
diet) respectively. Fish were fed twice daily until satiation for 28 days. At the end of experimental
period, fish was challenged i.p. with Aeromonas sobria and Pseudomonase fluoresces and kept
under observation for 14 days.
Saccaromyces castelli had antibacterial activity against Psudomonas anguilliseptica, Ps.
fluorescens, Aeromonas veronii and A. sobria in vitro with inhibition zones 38, 40, 13 and 42 mm in
diameters respectively. The best growth rate, specific growth rate and feed conversion ratio were
obtained with T2 and T3 compared to T^. Significance increased in the heamatocrite value,
respiratory burst, lysozyme activity and serum bactericidal activities among fish fed with diet
contained live yeast compared to control fish. Saccaromyces castelli supplemented diet had positive
effect on the total bacterial viable count in the intestine by decreasing its count than control group.
Also it increased antibody titer of A. sobria and Ps. fluorescence than control group. Fish of group
T2 and T3 had resistance against A. sobria and Ps. fluorescence while, fish of T3 gave relative level
of protection (RLP) higher than T2 against Pseudomonase fluorescence. So, Saccaromyces castelli
enhanced growth, immune response and resistance of O. niloticusagainst A. sobria and Ps.
fluorescens. |
