الفهرس | Only 14 pages are availabe for public view |
Abstract This study was conducted to investigate the role of two microalgae and their combinations in growth performance, hematological, biochemical, immunological and histopathological changes in Nile tilapia. A total number of 180 healthy Nile tilapia (Oreochromis niloticus) with an average body weight (31.89 ± 0. 29 g) were distributed into 4 groups that stocked in 12 glass aquaria (15 fish/aquarium/replicate). Fish groups were fed experimental diets as following; the first group (T0) fed basal diet only as control, the second & third groups fed basal diet supplemented with 0.5% Spirulina platensis (TS) and 0.5% Chlorella vulgaris (TC) powders; respectively. The fourth group (TSC) fed basal diet with combinations of the two algae powders with the same concentration (0.5% S. platensis and 0.5% C. vulgaris). The treatment continued for 60 days as feeding period followed by 10 days for challenged with pathogenic strains of Aeromonas hydrophila and Pseudomonas fluorescence. After feeding period, the growth parameters revealed significantly improved in TSC group, when compared to other groups. The hematological analysis showed non-significance changes in blood parameters among all experimental groups, except the leukocytic count was significantly up regulated in TC & TSC groups when compared to control. Additionally, hepatorenal and stress biomarkers (ALT, AST, Urea & Cortisol) exhibited non-significant changes among all fish groups. The immune status displayed enhancement that represented by significant elevation in Respiratory burst activity (RBA) among algal supplemented groups when compared to control group with non-significant change in IgM & NO values between all groups. During histopathological examination, normal tissues architecture and cellular details of intestine, liver, spleen & kidneys form all experimental fish groups were noticed without any obvious alteration lesions after feeding period. Moreover, significant improvement in intestinal morphometry (villi length & width, absorption area, tunica musularis thickness and number of goblet cells) as well as splenic morphometry (number and size of melanomacrophage centers, MMCs) in algal supplemented groups compared with control group. Following challenge infection, the cumulative survivability among experimental groups after 10 days of observations revealed significant increase in TC group, followed by TSC & TS groups when compared with control group with survival rate of 90%, 80%, &70 and 0%; respectively. The present study findings recommended the dietary inclusion of S. platensis and C. vulgaris with optimum doses in aquafeed as they strongly improved growth, and immune responses of Nile tilapia and their disease resistance against threatened bacterial pathogens. |