Author(s): SALAH MESALHY ALY, NASHWA MAHMOUD ABDEL ATTI, MOHAMED FATHI MOHAMED
Sixteen hundred Oreochromis niloticus were divided equally among five groups, each comprising four equal sized replicates, to evaluate the efficiency of a garlic-supplemented diet (10 and 20 g kg -1 diet fed) in the performance of O. niloticus . Group (1) was the control (fed on base diet). Groups (2 & 3) were fed on garlic- supplemented diet (10 and 20 g kg -1 diet fed) for one month, respectively, and groups (4 & 5) were fed on same doses of garlic- supplemented diet for two month, respectively. All groups were fed on the base diet after the period s of garlic-supplementation until Month 8. Body weight and bloo d parameters were recorded. Challenge infection with pathogenic Aeromonas hydrophila, was carried out immediately after feeding the test diets as well as Month 8. Survival and individual bo dy weights were recorded at the end of the trial. Studies on fish quality and shelf-life were also carried out. A non-significant incr ease was seen in the hematocrit values among all treatment grou ps. Statistically significant increases in total leukocytic count in treatment group 2 were also observed. Moreover, the nitr oblue tetrazolium value was significantly elevated after 2 month and the monocytic count was significantly increased in groups 2-5. There was no statistically significant increase in mean individual body weights of treatment groups 2-5 after one and two months, but there was a statistically significant increase after eight mo nths in all treatments except group 2. Survival rates were signif icantly higher in all treatments compared to the control. The relati ve level of protection against the challenge infection was higher in all treatment groups than in the control. The quality and shelf-life of the garlic supplemented tilapia was better than those of the contro l. Both dose rates of garlic induced a similar effect, enhancing immunity and health status. Consequently garlic improved th e growth performance. Moreover, fish quality and shelf-life were improved. However, further extensive testing, including full commercial cost benefit analysis, is necessary before recommending its application in aquaculture.