A preliminary investigation into the potential effect of Artemisia afra on growth and disease resistance in sub-adults of Oreochromis mossambicus

06 Nov 2019

This study investigated the potential of Artemisia afra on growth and disease resistance in Oreochromis mossambicus. Phytochemical analysis of A. afra was also undertaken. Five A. afra-based diets designated as D1, D2, D3, D4 and D5 were formulated and randomly fed to triplicate groups of 45 fish (32.5 ± 1g). At the end of feeding, Food Conversion Ratio and Specific Growth Rate values were not significantly different (F15,4 = 0.6, p > 0.05; F15,4 = 0.45, p > 0.05, respectively) between D1 and the other diets. Weight gain and feed intake were higher in D1, D2 and D3 than in D4 and D5, but no significant difference (ANOVA, p > 0.05) was found between treatments. This suggests that safe dosages were used. Phagocytosis and lysozyme activity were higher in fish fed D4 and D5 than those fed D1 and the other diets. White blood cells were also higher in fish fed the A. afra-based diets. To test for disease resistance, fish from each dietary treatment were injected with varying concentrations (0, 1 × 106 cfu, 1.5 × 106 cfu, 3 × 106 cfu, 4 × 106 cfu mL˗1) ofAeromonas hydrophila. Relative percentage survivalandthesurvival rateofO.mossambicuswerehigherin fishfedD4andD5,indicatingthatthe use of A. afra-based diets enhanced immunity of O. mossambicus. This is because A. afra contained a number of biologically active compounds that act as immunostimulants. High levels of total polyphenol (70.32 ± 3.5 mg100 g˗1), total phenols (88.65 ± 5.32 mg 100 g˗1), total flavonoids (181.5 ± 4.13 mg g˗1) and alkaloids (29.63 ± 3.58 g kg˗1) were recorded in A. afra.