Effects of dietary supplementation of local medicinal herbs on hybrid grouper juvenile (Epinephelus fuscoguttatus x Epinephelus lanceolatus)

• Main Author: Dayang Nur Jazlyn Abang Zamhari
• Format: Thesis
• Language: English; English
• Published: 2019
• Subjects: SH151-179 Fish culture
• Online Access: https://eprints.ums.edu.my/id/eprint/42791/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/42791/2/FIULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/42791/

In treating bacterial diseases in aquaculture, non-organic substances such as antibiotics have been commonly used. However, researchers have discovered that with its continuous usage, the bacteria became resistant to antibiotic. Thus, the usage of herbs in treating aquaculture diseases has gained interest worldwide. Present study was conducted to screen the antioxidant and antimicrobial properties of some local medicinal herbs (Experiment 1) and to determine the growth, feed utilization, apparent digestibility coefficient, blood analysis and survival after challenged with Vibrio harveyi VHJR7 of the hybrid grouper juvenile fed with diets supplemented with herbs through a feeding trial (Experiment 2). In experiment 1, methanolic extracts from four fresh local medicinal herbs; Piper betle (betel), Curcuma longa (turmeric), Etlingera coccinea (“tuhau”) and Clinacanthus nutans (snakegrass) were tested. The antioxidant activity was tested using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging activity. Meanwhile, the antibacterial activity was tested using the disc-diffusion method using four types of marine pathogens; Vibrio alginolyticus, V. anguillarum, V. harveyi and Vibrio parahaemolyticus. Concentrations of 0, 20, 50 and 100 mg/mL were tested for the antibacterial activity. A feeding trial was then conducted with the supplementation of the three best performing herbs in the diets; which were betel (D-betel), turmeric (Dturmeric) and tuhau (D-tuhau) at 0.5% of supplementation in the isoproteic (50%) and isolipid (12%) diets. Diet without herb supplementation was used as the control. Hybrid grouper, Epinephelus fuscoguttatus x E. lanceolatus juveniles with initial body weight of 8.91 ± 0.02g were fed with the experimental diets for 8 weeks. During the trial, triplicate groups of 20 fish were cultured in 100L fiberglass tanks for each experimental diet with a flow-through seawater system. The fish were fed with experimental diets until apparent satiation level twice a day. Results from the screening (Experiment 1) showed that the highest antioxidant activity was found in betel extract (more than 50% of activity), followed by turmeric (20 – 40%), tuhau and snakegrass (20 – 30%). Betel extract also showed strong antibacterial activity (>14.0 mm), followed by a moderate activity of tuhau (10 – 14mm), a weak activity of turmeric (<10mm) and no activity at all from snakegrass (0mm). Screening of these herbs in-vitro showed that among all the herbs tested, betel leaves extract gave the best results for the antioxidant and antibacterial activity. For the feeding trial (Experiment 2), highest growth was seen in fish fed D-turmeric, followed by D-tuhau while fish fed D-betel showed the lowest growth. However, the growth of fish fed D-turmeric and D-tuhau showed no significant difference than the control diet (p > 0.05). Better feed utilization was also observed in fish fed D-turmeric and D-tuhau compared to D-betel. Apparent digestibility coefficient (ADC) of protein and lipid of fish fed D-turmeric and D-tuhau were significantly higher than the control (p < 0.05). The herb supplementation did not affect the blood analysis except for the white cell count where lower values were obtained and higher platelet count was observed. When challenged with Vibrio harveyi VHJR7, fish fed D-betel showed highest survival amongst all and the superoxide dismutase activity in blood increased significantly after the challenge test. In conclusion, the herbs turmeric and tuhau improved the growth and feed efficiency of the hybrid grouper juvenile while betel provided better results in the challenge test.