Reconsidering the use of soy and alfalfa in southern white rhinoceros diets

Abstract

The captive southern white rhinoceros (SWR) population is not currently self-sustaining due to the reproductive failure of captive-born females. Our research into this phenomenon points to chemicals produced by plants common to captive diets, such as soy and alfalfa, as possible causes. In other species these chemicals, called phytoestrogens, are well known to cause fertility issues due to their ability to disrupt normal hormone function. Here we present a brief overview of how phytoestrogens impair fertility and propose a mechanism for how they do so in SWR. In addition, we summarize our past findings that suggest developmental exposure to phytoestrogens is a probable cause of the low fertility captive-born female SWR exhibit. Moreover, we present recent evidence from our own institution that suggests changing to a low-phytoestrogen diet may promote the reproductive success of previously infertile captive-born female SWR. As a result, we strongly suggest dietary phytoestrogen levels should be reduced in order to increase fertility of SWR in managed settings.