No they are not reliable. I don't know of one for cows, but I know for a fact that dogs are tested and test as breeds that they can't possibly be (well bred papered dogs with obviously known breeding testing as completely different breeds).
Cows are different. They are DNA checked much more often an with a much larger database due to trying to return lost cattle. Horses aren't DNA checked very often at all and therefore there just isn't enough lineage samples to match it up to. Posted via Mobile Device