My prayers have been going out to the families effected by it. I have to ask you folks that are more accustomed with the weather up there...is this a common type of thing, to have such serious storms that kill off herds? Only reason I ask is because this is at least the second instance like this in the last 2-3 years.
It was unusual to get this much snow, this fast, this early in the fall. An early fall snow, wet and cold for a short time is common and doesn't effect the livestock horribly.
The cattle and horses don't have their winter coats yet. And, they were still, most of them, on summer pastures. Summer pastures are usually farther from headquarters and have less protection from wind and cold.
The winds were also unusual. 50 and 60 mph sustained, and gusts to 80 mph for a long period of time. The livestock just kept drifting with the wind until they could go no more. Either stopped by a fence they couldn't go through or over, or dropped by exhaustion.
Many ranchers cattle are on their neighbors places and they have other peoples cattle on theirs. I know a family that has only two of their own animals still at home, while they have a couple hundred that belong to other people with their two.
In those situations everybody is leaving the well livestock where they are and whoever has them is caring for them. The focus is finding ones still alive that need attention.
Western South Dakota was hardest hit.