THE EFFECT OF PAWPAW SEED MEAL AND MORINGA SEED MEAL ON OVARIAN DEVELOPMENT AND EGG VIABILITY IN SEXUALLY IMMATURE MOZAMBIQUE TILAPIA (Oreochromis mossambicus)

Abstract

access to advanced biotechnologies to manage the precocious breeding strategy leading to overstocking in culture systems, which result in stunted growth and variable sizes of marketable fish. Developing suitable cost-efficient alternative methods to resource-poor communities in SSA to ensure sustainable tilapia production for food security purposes is warranted. A Tilapia culture efforts in Sub-Sahara African (SSA) countries are inefficient due to limited potential method to control the precocious breeding nature of tilapia is the use of natural plants components that contain endocrine disrupting compounds (EDCs). Several studies report on the antifertility effect of Pawpaw (Carica papaya) and Moringa (Moringa oleifera) seeds in certain livestock species. This study investigated the potential effect of Pawpaw (P) and Moringa (M) seed powders as phytogenics on ovary development in sexually immature Mozambique tilapia (Oreochromis mossambicus). The P and M seed powders were added to a commercial tilapia diet (NutroScience (Pty) Ltd, South Africa; the basal diet, BD) at inclusion levels of 0, 0.5, 1.0, 2.0, 5.0 and 10.0 g/kg BD, and fed to 1,650 sexually immature tilapia of unknown gender (2-8g; 30 fish per replicate; 5 replicates per treatment) for 60 days. After, 4 fish were sacrificed per replicate to assess the effects of P or M on ovary development. Fish fed 0g /kg BD, ovaries appeared normal, equal in size containing ochre coloured eggs. Egg production, ovulation and spawning were all affected, as evident in the difference in colour of the degrading eggs, as well as the absence of spawning. Eggs were observed in the ovaries of sexually immature fish, but spawning did not occur. Observations in fish fed diets included at 2.0, 5.0 and 10.0g P or M /kg BD showed deformities including unequal size, enlarged ovaries, twisted ovaries, a single and fused ovary. The study indicated that P and M dosage ≥2.0g/kg BD have a significant effect on normal ovary development and maturation in sexually immature female O. mossambicus. Thus, P or M seed powder can be used as potential EDCs to delay or suppress the attainment of sexual maturity in female tilapia, thereby, controlling tilapia precocious breeding. Sustainable availability of Pawpaw and Moringa seeds in SSA contributes to the attractiveness of their potential usage in the reproductive management of tilapia in commercial and small-scale tilapia culture systems.