A feeding trial was conducted to assess the effect of inclusion of dried powder of purslane, Portulaca oleracea, leaves in diets on growth, antioxidant, and immunological responses of Nile tilapia, Oreochromis niloticus, as well as its resistance to pathogenic bacteria, Aeromonas hydrophila. Fresh leaves of purslane were collected, dried, and mixed thoroughly with a basal fish diet at levels of 0.0 (control), 1.0, 2.0, and 3%. Fish (18.2 ± 0.4 g) fed one of the experimental diets up to apparent satiation twice a day for 7 weeks. At the end of the feeding trial, fish were intraperitoneally injected with pathogenic bacteria, A. hydrophila, and fish mortalities were observed and recorded up to 10 days post-challenge. Fish growth, weight gain, and specific growth rate were retarded significantly with increasing purslane levels in fish diets as compared to the control group. On the other hand, significant (P < 0.05) increases in plasmatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities accompanied with significant decreases in malondialdehyde (MDA) were observed with increasing purslane levels in fish diets. The respiratory burst (RB) activity and lysozyme value were significantly enhanced, while nitrous oxide (NO) decreased significantly with increasing purslane levels in fish diets over those of the control fish. After 10 days of the bacterial infection, no significant changes of MDA and SOD levels were observed, whereas CAT and GPX activities were significantly elevated. Additionally, RB and lysozyme activities were lower, while NO levels were elevated more than those before bacterial infection. Fish survival before and after bacterial infection was significantly affected by dietary purslane supplements, bacterial infection, and their interaction where dietary purslane improved the fish resistance to A. hydrophila infection in a dose-dependent manner. Purslane-fed fish showed highest relative percent of survival especially at an inclusion level of 3% (81.25%), whereas the control fish group showed lowest relative percent of survival (0.0%).
Manifestation pathologique due à l'action des microbes.