That's why I also specified blood testing for hormones and other blood "ingrediants" that might be related to fertility, in addition to minute exams of the whole reproductive system(in the case of euthanasia or accidental death-egg binding). Any sort of scientific testing whether gross necropsy(probably not too useful), lab necropsy(more useful) and/or blood testing(probably most useful) would most likely be helpful, since if nothing else, it could rule out various things.