Sexual parameters, digestive enzyme activities, and growth performance of guppy (Poecilia reticulata) fed garlic (Allium sativum) extract supplemented diets

Although many studies have assessed the various effects of garlic on fish, the impact of garlic on steroid hormones has not been studied. In the present study, the effect of aqueous garlic extract on sex steroid hormones, fry production, digestive enzyme activities, growth performance, and survival of Poecilia reticulata were evaluated. A total of 360 P. reticulata fries (0.013 ± 0.001 g) were randomly stocked in 12 experimental glass tanks (50 L) at a density of 30 fish per tank. The fries were fed diets supplemented with aqueous garlic extract at 0 (Control), 1.00 (G1), 1.50 (G2), and 2.00 (G3) ml/kg diet three times a day at a ratio of 2.5% of their body weight for a period of 120 days. Results demonstrated that the inclusion of garlic extract in the diet did not have any significant effect on growth performance and fry production. The survival of G2 treatment was significantly higher than the control, G1 and G3 (p <.05). The concentrations of sex steroid hormones (estradiol, testosterone, 17α-hydroxyprogesterone and progesterone) and the activity of digestive enzymes (protease, lipase, and amylase) were significantly higher in G2, than the control and other treatments (p <.05). Based on polynomial regression models, the recommended dietary concentration of garlic extract for P. reticulata should be 1.64 ± 0.03 and 1.63 ± 1.01 ml/kg to obtain higher activities of digestive enzymes and sex steroids, respectively.