Missouri Emergency Response Service (MERS), a Large Animal Rescue group, has reported that over the last 4 weeks there has been a spike in the number of calls that they are getting for horses that have fallen into frozen ponds, or become trapped on top of the frozen surfaces.
Although many people must leave their horses out in this type of weather, it is very important to make sure that the horses have access to fresh water. If a heated water trough or heated water bucket is not an option, it is extremely important to keep ice chipped away in order to keep the horses from venturing out onto the pond. The downside from trying to keep ice chipped away in this temperature range, is that it must be done often.
As a general rule, horses will not go out onto a frozen pond, if they have a source of fresh water.