Effects of Phytoestrogens on Sensitive Life History Stages in Channel Catfish

Effects of Phytoestrogens on Sensitive Life History Stages in Channel Catfish

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Soybean meal has been proposed as an alternative protein source in aquaculture feeds. Soybean meal partially or completely replaces fishmeal as the major protein component in commercial catfish diets. Although soybean substitution has shown promising results when replacing fishmeal in feeds for numerous herbivorous and carnivorous aquaculture species, there are a number of potential drawbacks that need to be considered. One component in need of investigation is the presence of phytoestrogens in plant protein components. Phytoestrogens are plant-based estrogen mimics that serve in the plants as phytoalexins, compounds that provide plants with protection from viruses, fungi, bacteria, and insects. Genistein represents the largest proportion of phytoestrogens in soybeans and have the potential to alter cellular functions associated with spermatozoa production and energy utilization. Genistein was found to bind with steroid-binding-proteins within channel catfish Ictalurus punctatus to produce estrogen receptor mediated effects in the form of vitellogenin production from the liver. Genistein competed with radiolabeled estradiol for hepatic estrogen receptors (ERs) in both the male and female channel catfish. Relative binding affinities in male ERs were higher (2.72) than those in females ERs (1.17) for genistein. Channel catfish fed increasing concentrations of genistein (0, 2, 4, 8 mg/g) between 5-140 and 60-150 days post hatch displayed significant deviations from expected phenotypic sex in a dose dependant manner. Additionally, intersex individuals were identified at all treatment concentrations for catfish fed between 5 and 140 days post hatch. When walleye Sander vitreus and channel catfish spermatozoa were incubated in vitro with graded concentrations of genistein, ATP content was significantly lower compared to control treatments at several incubation concentrations and was significantly related to fertilization rate. Fertilization rate was significantly dependant on genistein incubation concentrations (P a‰c 0.01). Logistic regression showed a significant relationship between genistein concentration and fertilization in channel catfish ( P a‰c 0.01). Although in vitro examinations revealed alterations in several spermatozoa quality parameters and fertilization capacity, in vivo work showed no significant declines in the same parameters. Overall this work revealed that the impacts of phytoestrogens, particularly genistein, can alter the normal physiological functions of sex determination and reproduction at both early and late life history stages.The Institutional Animal Care and Use Committee of Southern Illinois University Carbondale approved in advance all ... were recorded using a digital video camera (Sony Digital Handycam, Model DCR-TRV350, New York City, New York )anbsp;...

Title:Effects of Phytoestrogens on Sensitive Life History Stages in Channel Catfish
Author:Christopher C. Green
Publisher:ProQuest - 2007


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