What is "cow sense?"

Cow sense in a horse means herding ability. A horse with "cow" is one that can read a cow, anticipate its motions, and has the will to face one down. (In some cases this can mean a little bit too much of that, in others, cowy horses initially show fear of cattle).

Although horses don't have a natural prey drive to turn into herding ability the way dogs do, the actions of dominant horses in the herd can be transformed in this way.