Donkey will handle the problem. But I've seen mares run a calves mom off and take over the calf. Finally had to pen the cow and calf up so it could suck. On another note had a neighbor come by a few years ago and say one of my dogs was chasing his cows. Picked up my 45 off the nightstand and walked out on the porch where my two dogs were laying. Asked him which one and he said that black one. Turned around and capped the dog in the head right there. No more problems. Don't like them chasing mine and won't have one that chases either