“…However, there are significant challenges in inclusion of fertility end points in toxicity studies, including irregular cycling, making cycle times difficult to calculate, effect of housing conditions on cycling, the long time required to establish baseline menstrual cycle, and the lack of information to aid decisions on what constitutes a significant effect [36]. There is also a concern that the increasing use of sexually mature primates for general toxicity studies for the sole purpose of assessing fertility will put a strain on animal supply and may not be sustainable in the long term [9].…”