There were cows in one of my spots in NC that I hunted the last 4 years. I'm not sure how much they bothered the deer but they aggrivated the hell out of me! I would get out of my stand and run them off, sometimes more than once in a sit.

If the deer are used to the cows being around like they are now, I would think that could throw them off a bit. They should get used to them...in time.