Partial or total replacement of fish meal by plant protein affects gonadaldevelopment and plasma 17 beta-estradiol levels in female Nile tilapia

This study was conducted to evaluate the effect of plant protein-based diet s on gonadal development and plasma 17 beta -estradiol (E2) level in female Nile tilapia Oreochromis niloticus. Fish with a mean body weight of 6.7 (0 .1) g were fed four different diets with the same digestible protein (DP) a nd digestible energy (DE) containing graded levels of a mixture of plant in gredients as partial or total replacement of fish meal protein for 20 weeks . The control diet (D0) was based on fish meal, two diets containing 33% (D 33) and 66% (D66) of plant protein, and one diet containing only plant prot ein (D100). Fish were sampled at 12 and 20 weeks. No significant difference s were found in different stages of oocyte development and plasma E2 levels between tilapia fed diets D0 and D100 at 12 weeks. Eight weeks later tilap ia fed diet D0 showed a higher (P < 0.05) level of E2 than the D100 group. This difference and the reduced proportion of vitellogenic and mature oocyt es demonstrated that diets containing only plant protein are less efficient in terms of tilapia growth and consequently ovarian development.