Impact of dietary soybean inclusion on the endocrine disruptive effect in female brood stock of Cyprinus carpio

Abstract

Phytoestrogens, mostly found in legumes, mimic animal estrogens and induce either pro- or anti-estrogenic activity. A feeding trial for matured Cyprinus carpio females was carried out to assess the endocrine disrupting effect of phytoestrogens in SBM and to suggest a dietary inclusion of soybean meal for broodstock of carps. The fish were fed diets containing graded levels of soybean meal (SBM-0, 15, 20, 25, 30, 35, and 40%) for 60 days. To assess the endocrine disruption, sex hormone profiling, gene expression analysis of candidate genes, and histological examinations were conducted. Serum T3, serum vitellogenin, and mRNA levels of cyp19a1, cyp19b, and erβ were found to be higher in fish groups fed with diet containing low levels of SBM (SBM 15, 20, and 25), and significantly lower in high SBM diet (≥30%) fed groups. Serum concentrations of cholesterol, cortisol, and the mRNA level of 20βHSD all decreased as SBM increased. Increased levels of testosterone, estradiol, and the mRNA for the erα gene were observed in the diet when SBM was incorporated into the diet. In the treatment groups with ≥30% inclusion of SBM, the number of vitellogenic oocytes and the gonadosomatic index were significantly lower than the groups with low inclusion levels. Thus, soybean meal can be included in the diet of female carp broodstocks up to 25% without disrupting the reproductive function. However, an inclusion level beyond 25% could harm the endocrine axis, subsequently capable of impacting reproductive performance.