Dietary Euphorbia hirta Extract Improved the Resistance of Sharptooth Catfish Clarias gariepinus to Aeromonas hydrophila

Effect of dietary Lagnaria breviflora leaves extract on the growth performance, haematological, antioxidative and immune responses of African catfish (Clarias gariepinus) juveniles

The effects of dietary Lagnaria breviflora leaves extract (LBLE) on the growth performance, feed utilisation and haematological parameters of juveniles African catfish, Clarias gariepinus (mean = 8.45 ± 0.6 g) raised in a flow water (mean temperature 26.7°C, mean pH 7.52, mean dissolved oxygen 6.05 mg/L) were assessed in this study. Diets (400 g/kg crude protein; 4631.5 kcal/kg gross energy) supplemented with LBLE at levels of 0 (control), 0.5, 1.0, 1.5 or 2.0 g/kg diet were served to fish in triplicates (each replicate has 20 fish) until they appeared satiated for 12 weeks. Then, they were challenged with Aeromonas hydrophila infection for further 2 weeks. Fish served dietary LBLE had considerable higher weight gain (64.76 g) and specific growth rate (765.5% g/day) than the fish group fed with the control diet with a reduced feed conversion ratio (1.45) (p < 0.05). Compared to fish fed with the control diet, the villi height (146.30 µm) and width (284.35 µm) of the intestines increased greatly in a dose (LBLE in diets) dependent order. Similarly, dietary LBLE increased (p < 0.05) the packed cell volume (46.11%) and haemoglobin (17.03 g/dL), whereas 1.5 g of LBLE increased the counts of white blood cells. Glutathione S-transferase (769.43 U/mg protein), glutathione peroxidase (84.14 U/mg protein) and superoxide dismutase (433.15 U/mg protein) activities were significantly higher (p < 0.05) in fish fed with diets supplemented with LBLE compared to the control one. Additionally, dietary LBLE increased phagocytic and lysozyme activities and protected C. gariepinus against bacterial infections where the lowest death was observed in the fish fed on the diet containing 1.5 g LBLE/kg feed. These findings showed that the fish fed with LBLE/kg diet improved their immune system, antioxidant and growth performance in addition to providing protection from A. hydrophila infection with the optimum dose of 1.80 g/kg diet.

Effects of dietary Euphorbia heterophylla extract on the growth performance, physiological, antioxidative and immune responses of Clarias gariepinus juveniles

Effects of dietary Euphorbia heterophylla extract (EH) on growth performance, feed utilization and haemato-biochemical parameters in African catfish, Clarias gariepinus, juveniles were evaluated in this study. Diets fortified with EH at 0 (control), 0.5, 1.0, 1.5 or 2.0 g/kg were fed to the fish to apparent satiation for 84 days before challenging it with Aeromonas hydrophila. The weight gain, specific growth rate and protein efficiency ratio of fish fed EH-supplemented diets were significantly higher but lower feed conversion ratio (p < 0.05) than the control group. The villi height and width at the proximal, mid and the distal of the guts rose significantly with the increasing levels of EH from 0.5 to 1.5 g than the fish fed basal diet. Dietary EH enhanced (p < 0.05) the packed cell volume and haemoglobin, whereas 1.5 g EH boosted white blood cell, in relation to their counterpart in the control group. There were significant increase in the activities of glutathione-S-transferase, glutathione peroxidase and superoxide dismutase (p < 0.05) in the fish that were fed diets supplemented with EH than the control. Dietary EH also enhanced phagocytic activities, lysozyme activities and relative survival (RS) of C. gariepinus than the control group, with the highest RS obtained in fish that were fed diet containing EH at 1.5 g/kg level. These results revealed that the fish fed 1.5 g/kg dietary EH promoted growth performance, antioxidant and immune profiles, as well as protection against A. hydrophila infection.

Role of phytobiotics in relieving the impacts of Aeromonas hydrophila infection on aquatic animals: A mini-review

Aeromonas hydrophila is a ubiquitous bacterium with various hosts that causes mass mortality in farm-raised fish species and significant economic losses. The current antibiotic treatment is ineffective in controlling this bacterium infection in aquaculture species. Therefore, an evaluation of potential phytobiotics is needed to find an alternative antimicrobial agent to reduce the over-reliance on antibiotics in aquaculture and safeguard public and environmental health. Furthermore, the rise in antibiotic resistance cases among pathogenic bacteria indicates an urgent need for new fish and shellfish health management solutions. In this context, phytobiotics applications in aquaculture can be defined as any medicinal plant-based antimicrobial agent used in fish and shellfish health management. This review will focus on the impacts of Motile Aeromonas Septicemia (MAS) due to A. hydrophila in aquaculture, the potential of phytobiotics in enhancing the tolerance of aquaculture species against MAS and the combination of phytobiotics with other antimicrobial and therapeutic agents against MAS.