Translate the following English sentence to French:
"Of course, it is hard when just one animal out of a whole herd is sick, as it is very difficult to discern if there are animals which appear healthy but which may fall ill later on. That is precisely why we are proposing this measure."
Car assurément, il est très difficile, quand un animal est atteint au sein d' un troupeau, de distinguer s' il en est d' autres, apparemment en bonne santé, qui pourraient contracter la maladie ultérieurement, et c' est pourquoi cette mesure est proposée.