 A lack of breeding records resulted in fertility problems, and there was a significant amount of foal mortality, due to jacks being used to cover horse mares before jennies of their own kind, resulting in late-born foals that were vulnerable to cold fall and winter temperatures.Despite these husbandry issues, one author, writing in 1883, stated that "mule-breeding is about the only branch of agricultural industry in which France has no rival abroad, owing its prosperity entirely to the zeal of those engaged in it.