Antifertility effect of Ocimum sanctum Linn in Oreochromis mossambicus

Abstract

After carps, tilapia is the second most culturable fish. However, due to its rapid reproduction, wild tilapia (Oreochromis mossambicus) poses a severe threat to the freshwater system, particularly in aquaculture. Approximately 75% of published research shows that introducing tilapia into aquaculture has a negative impact. Similarly, due to the risk of side effects, hormonally administered mono-sex tilapia is not satisfying consumer demand. Therefore, this study aimed at determining the effect of the Tulsi (Ocimum sanctum) plant on the fertility of males and females’ tilapia (Oreochromis mossambicus), by examining the histomorphological alternation of testis and ovaries, estimating the gonadosomatic index, and analyzing the level of plasma testosterone. A 90-day feeding trial in a replicate of three was conducted in fiberglass tanks. Uniform size and active O. mossambicus, average body weight 3.4± 0.4g were equally distributed in 12 fiberglass tanks (20 fish/tank) having well-aerated water. The experiment was divided into four groups named control group Tο, and three treatment groups T1, T2, and T3 groups. Tilapia fingerlings in the Tο group were fed with 40% crude protein basal diet while the other, three groups were fed 40% crude protein basal diet supplemented with graded level 1%, 2%, and 3% of Tulsi (O. sanctum) by weight of the diet. Initially, fish were provided feed at the rate of 7% body weight, three times a day. Afterward, based on the body weight, feeding frequency and ratio were changed. Results indicated a dose-dependent significant effect of O. sanctum on the growth performance of O. mossambicus. At the end of the study, the T3 group showed the highest weight gain, SGR, and the lowest FCR. The addition of O. sanctum to the diet had a considerable impact on the apparent digestibility of nutrients, i.e., an increase in apparent digestibility of protein, fat and dry matter as compared to the control group. In addition to these O. sanctum also showed significant (P>0.05) dose-dependent positive effects on blood indices i.e., the T3 group showed the highest RBCs and WBCs count, hemoglobin level, HCT%, MCH, MCHC; significantly higher (P>0.001) activity of antioxidant enzymes SOD, POD, CAT, GSR, GST, GPX, GSH, and the lowest LPO level. Metabolic enzymes LDH and AST did not show any significant difference (P<0.05) among the control and treatment group while ALT showed a dose-dependent lower level in O. sanctum fed group. The GSI of both male and female fish was negatively affected by O. sanctum supplemented diet in a dose-dependent manner. Both sexes males and females at higher doses showed about 35% and 28% respectively decrease in GSI as compared to the control group. The histology of testis and ovaries of fish fed O. sanctum indicated deformation in seminiferous lobules and interlobular tissues in testis and necrosis, atresia, increase in vacuolation, and fusion of ova in ovaries. Moreover, a significant (P < 0.001) increase in plasma testosterone and estradiol level was also observed in O. mossambicus fed males and females respectively. Based on results, the O. sanctum plant could be recommended for improving the growth, health status, and controlling the reproduction of O. mossambicus. Further studies are needed to elucidate the hormonal level impacts and to determine the optimum treatment regime for the induction of 100% infertility.