title: Estrogenicity of captive southern white rhinoceros diets and their association with fertility.
abstract: The captive southern white rhinoceros (SWR) population is not currently self-sustaining, primarily due to poor or absent reproduction of captive-born (F1+) females. In this study, we investigate the role of dietary phytoestrogens in this reproductive phenomenon by characterizing activation of SWR estrogen receptors (ESRs) 1 and 2 by diet items from nine North American institutions and comparing female SWR fertility to total diet estrogenicity. Of the diet items tested, alfalfa hay and soy and alfalfa-based commercial pellets were found to be the most potent activators of SWR ESRs. In contrast, most grass hays tested were not estrogenic. The estrogenicity of total diets varied across the institutions surveyed and the degree of diet estrogenicity was positively associated with the percentage of the total diet comprised by pellets. Comparisons of fertility records of the institutions surveyed showed no significant relationship between diet estrogenicity and fertility for female SWR conceived or born in the wild (F0). However, for F1+females, there was a significant negative relationship between institutional diet estrogenicity and fertility. Taken together, these data suggest that developmental exposure to phytoestrogens may be the cause of poor fertility in captive-born female SWR. Whether the low fertility of the current population of captive-born female SWR is permanent or can be reversed by removing phytoestrogens from the diet remains unclear. However, our findings suggest that in order for the SWR population to become self-sustaining, the development and feeding of low phytoestrogen diets should be strongly considered.
authors.affiliation: San Diego Zoo Global, Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, United States. Electronic address: ctubbs@sandiegozoo.org.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Tubbs
authors.affiliation: San Diego Zoo Global, Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, United States.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Moley
authors.affiliation: San Diego Zoo Global, Life Sciences, P.O. Box 120551, San Diego, CA 92112, United States.
authors.forename: Jamie A
authors.initials: JA
authors.lastname: Ivy
authors.affiliation: South-East Zoo Alliance for Reproduction and Conservation, 581705 White Oak Road, Yulee, FL 32097, United States.
authors.forename: Lara C
authors.initials: LC
authors.lastname: Metrione
authors.affiliation: San Diego Zoo Global, Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, United States.
authors.forename: Sydney
authors.initials: S
authors.lastname: LaClaire
authors.affiliation: San Diego Zoo Global, Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, United States.
authors.forename: Rachel G
authors.initials: RG
authors.lastname: Felton
authors.affiliation: San Diego Zoo Global, Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, United States.
authors.forename: Barbara S
authors.initials: BS
authors.lastname: Durrant
authors.affiliation: Mars Hill University, P.O. Box 6671, 100 Athletic Street, Mars Hill, NC 28754, United States.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Milnes
mesh_terms: D000818:Animals; D004032:Diet; D004967:Estrogens / Q000378:metabolism*; D005247:Feeding Behavior; D005260:Female; D005298:Fertility; D010527:Perissodactyla / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D004967:Estrogens; D011960:Receptors, Estrogen; D011994:Recombinant Proteins
keywords: Estrogen receptors; Phytoestrogens; Rhinoceros