Regulatory roles of Pawpaw (Carica papaya) seed extract on growth performance, sexual maturity, and health status with resistance against bacteria and parasites in Nile tilapia (Oreochromis niloticus)

Papaya (Carica papaya) is one of the plants that represent a major source of bioactive substances that are cheaper and non-toxic, such as antibiotics. It is globally used as a supplement diet for positive effects in pharmacological activities. In this regard, the current study sheds light on the possible roles of papaya seed methanolic extract (PSE) as a dietary supplement to improve growth performance, sexual maturity, carcass composition, immunity responses, histological structure of gonads, and anti-pathogenic activity (Aeromonas hydrophila) at the end of a feeding trial extend for ten days of Nile tilapia, with special reference to its potential effect as resistance against parasitic (Cichlidogyrus tilapiae). Four experimental groups with four replications of Nile tilapia fry (0.5 +/- 0.1 g as 20 fish per replication) were fed (0, 0.5, 1.0, and 2.0 g/kg PSE in diets) for 20 weeks. Results showed that fish dietary supplementation with PSE had a significantly positive (P < 0.05) effect on growth performance, feed utilization, digestive enzyme, carcass composition, antioxidant, immunity responses, and hematological and biochemical indices, especially PSE 2.0 g/kg than control diet. Furthermore, PSE had a positively affected fish mortality after injection with A. hydrophila and in vitro positive efficacy against C. tilapiae. Fish fed with dietary PSE increased the sex ratio in favor of male fish by achieving a 77% male phenotype. Conclusively, this study declared that PSE extract, specifically 2 g/kg, could enhance growth and health through the modulation of innate immunity and a positive effect against disease in fish. Additionally, it reduced the reproductive performance of Nile tilapia by reducing GSI, which subsequently affected the gonadal histology leading to infertility.