Assessment study on the use of Pawpaw; Carica papaya seeds to control Oreochromis niloticus breeding

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

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.

Effects of some dietary crude plant extracts on the growth and gonadal maturity of Nile tilapia (Oreochromis niloticus) and their resistance to Streptococcus agalactiae infection

A 90-day feeding trial was conducted on the growth performance, feeding efficacy, body indices, various hematological and plasma biochemical parameters, and histopathological examination of the gonads from male and female Nile tilapia fingerlings when fed different crude plant extracts from Cinnamomum camphora, Euphorbia hirta, Azadirachta indica, or Carica papaya at 2 g kg(-1) compared to a control diet. This was followed by a 14-day challenge to Streptococcus agalactiae. All treatments were triplicated, and each treatment consisted of 30 fish. Results showed that C. papaya extracts were the most effective at delaying gonadal maturation to both male and female tilapia, as well as significantly increasing (P < 0.05) growth performance compared to the control treatment. Similarly, dietary C. camphora and E. hirta extracts also significantly improved growth, while no significant growth effect was detected between the A. indica and control treatments (P > 0.05). Further, crude body lipid was lower in the C. camphora, E. hirta and C. papaya treatments, but was only significantly lower for the E. hirta treatment compared to the control. Meanwhile, none of the hematological or biochemical parameters were significantly affected, although plasma ALT was significantly lower for tilapia fed A. indica compared to the control. After the 14-day bacterial challenge, tilapia fed C. camphora supplementation had significantly higher survival, compared to the control, but was not significantly higher than the other supplemented diets. Results indicate that dietary C. papaya extract can significantly promote growth and delay gonadal maturation to both male and female tilapia, while C. camphora was the most effective prophylactic to S. agalactiae and may be a cost-effective and eco-friendly alternative to antibiotics.