Effects of Varying Dietary Levels of Hibiscus rosa sinensis Leaves Powder on Growth and Gonads Development in Nile Tilapia Oreochromis Niloticus (Linnaeus, 1758)

Abstract

Aims: The purpose of this study was to explore the possible use of Hibiscus rosa sinensis leaf powder as a reproductive inhibitor in Oreochromis niloticus
 Place and Duration of Study: From 10th February to 21st June 2021 at the Kanhé-Moyo Integrated Fisheries and Aquaculture Research and Application Farm located in the locality of Baho'o belonging to the Baham District,in the West Region of Cameroon
 Study Design: 720 Oreochromis niloticus fingerlings with an average weight of 13±2.5g were randomly distributed in 12 happas arranged in an earthen pond measuring approximately 10 x 20 m and fed 3 experimental diets, formulated from a control diet to contain Hibiscus rosa sinensis leaf powder at doses of 3.5, 4.5 and 5.5 g/kg of feed respectively.
 Methodology: After 45 days post-treatment, survival and zootechnical growth parameters were assessed. Histological examination of the gonads was used to determine the impact of treatment on gonadal development at 45 and 65 days post-treatment respectively.
 Results: The results show that the different treatments had a similar effect on survival (P˃0.05), with an average value of 97.91 ± 3.81%. Analysis of the growth parameters of fishes from the different batches treated with different doses of H. rosa sinensis leaf powder revealed that the dose of 4.5 g/kg of H. rosa sinensis had a significantly greater effect than the other treatments applied in terms of Mean Final Weight (with a mean value of 24.77±0.27g), Mean Weight Gain (with a mean value of 3.63±1.18 g), mean specific growth rate (with a mean value of 1.13 ± 0.40%/day) and Mean Daily Gain (with a mean value of 0.25±0.08 g/d). However, analysis of the gonado somatic index at 45 and 60 days post-treatment of batches treated with different doses of H. rosa sinensis leaves revealed a significantly higher effect of the 3.5 g/kg dose on the gonado somatic index in both males and females. Observation of the testicular structures of the males from the treated batches revealed alterations reflecting an inhibition of gonadal development, which justifies the low gonado somatic index values observed in these different treated batches compared with the control batches. These alterations were also observed in the ovarian tissues of the treated females both at 45 and 60 days post-treatment. However, observations of the gonadal structures of satellite males and females at 60 days post-treatment revealed partial restoration of gonadal tissue in both males and females.
 Conclusion: The results of this study indicate that Hibiscus rosa sinensis leaves could be used as an alternative ecological method for inhibiting reproduction in Oreochromis niloticus. The results will help local producer networks to improve tilapia production.