No abstract

Aqueous and methanol extracts of lemon Citrus limon peel, Euphorbia hirta (aerial parts), and fenugreek Trigonella foenum-graecum seeds were tested for their in vitro antimicrobial activities against the bacterium Aeromonas hydrophila. A swab paper disk method showed that the methanol extract of E. hirta (EHE) had the largest inhibition zone and the lowest minimal inhibitory concentration compared to all other herbal extracts. Based on these results, EHE was included in the diets of Sharptooth Catfish Clarias gariepinus at 0 (control), 2, 5, or 7 g/kg of diet (experiment 1). Each treatment was conducted in triplicate, with 30 fish (mean weight ± SE = 9.4 ± 0.4 g) in each replicate. After 30 d, the growth, feed intake, hepatosomatic index (HSI), and plasma biochemical parameters were measured. With a separate batch of Sharptooth Catfish, the efficacy of the EHE diets in conferring fish resistance to A. hydrophila over 30 d was compared to that of a diet containing oxytetracycline (OTC; experiment 2). Six treatments were conducted in triplicate groups of 30 fish (mean weight ± SE = 9.0 ± 0.3 g); the Control fish were fed the control diet and were not injected with A. hydrophila, while the Control-AH and OTC-AH groups were infected with A. hydrophila and were fed either the control diet or the diet containing OTC at 1 g/199 g. The other three treatments included fish that were injected with A. hydrophila but fed diets with increasing EHE at 2, 5, or 7 g/kg. Experiment 1 showed no change to growth, feeding efficiency, HSI, or plasma biochemical parameters. In experiment 2, however, fish that were fed dietary EHE at 5 g/kg had significantly lower mortality than the Control-AH group, with further resistance observed for fish fed EHE at 7 g/kg. Dietary OTC was more effective than EHE as a prophylactic to A. hydrophila infection in Sharptooth Catfish. Nevertheless, EHE can potentially be a valuable dietary supplement to improve the resistance of Sharptooth Catfish to A. hydrophila infection. Received May 3, 2017; accepted August 24, 2017.

Two experiments were simultaneously conducted with Morus alba (white mulberry) foliage extract (MFE) as a growth promoter and treatment of Aeromonas hydrophila infection in separate 60 and 30 days trail (Experiments 1 and 2, resp.) in African catfish (Clarias gariepinus). In Experiment 1, four diets, control and control supplemented with 2, 5, or 7 g MFE/kg dry matter (DM) of diet, were used. In Experiment 2, fish were intraperitoneally infected with Aeromonas hydrophila and fed the same diets as experiment 1 plus additional two diets with or without antibiotic. Results of experiment 1 showed that growth was unaffected by dietary levels of MFE. Treatments with the inclusion of MFE at the levels of 5 and 7 g/Kg DM had no mortality. Red blood cells (RBC), albumin, and total protein were all higher for the treatments fed MFE (5 and 7 g/Kg DM). Results of experiment 2 showed RBC, hemoglobin, hematocrit, globulin, albumin, and total protein improved with the increase in MFE in the infected fish. The dietary MFE at the level of 7 g/kg DM reduced mortality rate. In conclusion, MFE at the level of 7 g/kg DM could be a valuable dietary supplement to cure the infected fish.

Medicinal plants have been successfully used to enhance the growth and immunity of fish during recent decade. The experiments herein were designed to assess the dietary effects of oak acorn (Quercus brantii) extract (OAE) on blood parameters, serum and skin mucus immune responses and resistance antibacterial activities of rainbow trout (Oncorhynchus mykiss) skin mucus against Yersinia ruckeri and Streptococcus iniae. Four hundred and fifty fingerlings (10.45 ± 0.24 g) were randomly stocked in fifteen tanks and fed experimental diets containing 0 (control), 100 (OAE1), 200 (OAE2), 400 (OAE3) and 600 (OAE4) mg/kg of OAE for eight weeks. At the end of the experiment, neutrophils (NEU), white blood cells (WBC) and hematocrit (Ht) and haemoglobin (Hb) levels significantly increased in the dietary treatments compared to those of the control. Higher lysozyme (Lys) activities and agglutinations (Agglu) were found in OAE2, OAE3 and OAE4. The alternative complement activity (ACH50) increased in supplemental the level of total immunoglobulin (total Ig) and skin mucus protease was highest in OAE3. The lysozyme activity of skin mucus and alkaline phosphatase (ALP) was enhanced in the OAE2, OAE3 and OAE4 groups. In vitro antibacterial activity tests showed that skin mucus effectively kills Y.ruckeri and S.iniae. Our findings further revealed the beneficial effects of dietary OAE on innate and mucosal immune responses, as well as the antibacterial activity of skin mucus of rainbow trout fingerlings.