As others have said Aladdins slippers.
You get these from the animal being on wet ground without enough hardness to wear away the toe nails.
As these progress rather than the animal walking on its tip toes (as it should) it falls back onto its hocks, which then get rubbed raw and get infected and the animal goes lame.
It is one of biggest challenges when keeping livestock, and unless you keep on top of it it is one of the biggest reasons for poor productivity especially in dairy cattle. I once had the misfortune of working for a short time on a 600 cow dairy farm. The boss was so mean he refused to spend any time or money on foot trimming. Lots of the cows were lame and they were sent off as culls. Average life of the dairy herd was three lactations. And he wondered why he wasn’t making money.
In the deer herd, these are the ones that should be culled before others. The signs are limping and generally poor condition. You will see the poor condition - they look like junkies - dull coat, stiffness of movement, sunken eyes etc. - chances are its due to feet, which is due to cold wet weather.