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An 84-day feeding trial was carried out to evaluate the effects of aqueous Psidium guajava leaf extract (PGE) on growth, intestinal morphology, physiology, immune response and susceptibility of Oreochromis niloticus to Aeromonas hydrophila. Diets containing 0% (P0), 0.25% (P1), 0.50% (P2), 0.75% (P3) and 1.00% (P4) PGE were fed to triplicate groups of fish (mean weight; 1.32 ± 0.04 g) for 84 days. After the 84-day feeding trial, test fish were injected with pathogenic A. hydrophila and then fed for 14 days. More feed were consumed in groups of fish fed PGE-treated diets and resulted in significantly higher weight gain and feed intake. Incidentally, there was an increase in the calculated area of absorption of fish fed PGE diets, as accounted for by marginally higher villi length and width. Antioxidant and immune response were improved with PGE inclusion in diets as total protein, superoxide dismutase, glutathione peroxidase and glutathione S-transferase significantly increased (p < 0.05) in fish fed PGE diets. Results of the challenge test with A. hydrophila revealed that the highest mortality (100%) was recorded in P0. This study revealed that inclusion of P. guajava extract in the diet of O. niloticus improved growth, nutrient utilization, immune system and survival of O. niloticus fingerlings. K E Y W O R D S Aeromonas hydrophila, growth, immune response, Oreochromis niloticus, Psidium guajavaChanges in weight were measured fortnightly (Orisasona, Falaye, Ajani, & Kareem, 2017) and values used in growth and nutrient utilization parameter determination. | Weight gainThis is as final weight of fish (W2) less initial weight (W1)Weight gain (g) = W2 − W1

There is a growing concern on the safety of frozen fish imported from various parts of the world where the levels of contamination of water bodies may not be well ascertained and regulatory measures not strictly adhered to. Concentrations of four heavy metals (Lead (Pb), Cadmium (Cd), Copper (Cu) and Mercury (Hg)) in the muscle, gill and liver were investigated for three most consumed frozen fish species (Umbrina canosai, Clupea harengu and Scomber scombrus) within Ibadan, metropolis. Samples were digested as described by FAO/SIDA. The concentrations of metals were quantified using a Varian AA240 Fast Sequential Flame Atomic Absorption Spectrophotometer (AAS). Heavy metals like Cd, Cu and Hg were significantly higher (p<0.05) in the liver of the three species than in the muscle and gills. There was no significant difference in the Pb concentration for the three organs in S. scombrus, whereas, Pb was significantly higher in the liver of U. canosai (9.73 mg kgG 1) and C. harengus (4.40 mg kgG 1) than in the muscle (6.92 and 2.11 mg kgG 1 , respectively) and gill (8.73 and 2.52 mg kgG 1 , respectively). Copper concentration was marginally higher in S. scombrus (5.06 mg kgG 1) with the least value recorded in U. canosai (3.28 mg kgG 1). However, no significant variation (p>0.05) was observed in the muscle Cd, Cu and Hg levels for the three species. Comparatively, S. scombrus has the highest concentration of heavy metals. This study revealed that the heavy metals investigated in the major organs and flesh was all above the limits recommended by World Health Organization.

The growth, gut ecology and immunocompetence of Oreochromis niloticus and the resistance to Aeromonas hydrophila were investigated after been fed with diets containing dietary Curcumin longa for 12 weeks. Diets were formulated to contain 30% crude protein with diet TC1, TC2, TC3, TC4 and TC5 having 0% (control), 0.25%, 0.5%, 0.75% and 1.0% turmeric powder, respectively. Diets were allotted to groups of O. niloticus (mean weight of 1.29± 0.15 g) and replicated thrice for 84 days. Results showed that the highest mean final weight (4.79±0.04 g) was obtained in TC3 and corresponded to the treatment with the highest feed intake. A significantly high (p<0.05) specific growth rate (SGR) was observed in TC3 (0.73±0.03 %day−1) while TC4 (0.57±0.02 %day−1) gave the lowest value. The highest microbial load in the gut was observed in TC1 groups and the least in TC4 groups. Red blood cell count, hemoglobin, packed cell volume did not show significant variation (p>0.05) across treatments. However, white blood cell (WBC) count was significantly higher in TC1 (control). There was an improved immunocompetence, as aspartate aminotransferase (AST) progressively reduces in fish fed supplements. Similarly, there was a better oxidative response in the treated groups with reduced hydrogen peroxidase, increased total protein and glutathione peroxidase. Mortality ranged from 25% in TC4 to 95% in TC1 after the challenge test with A. hydrophila. This study showed that C. longa inclusion at 0.5% is more beneficial when growth and health status of O. niloticus juveniles are considered.

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