I have never noticed that. I acually have taken many deer while out working cattle. Deer and cattle feed on different things. Cows eat grass, deer eat forbs. I keep a rifle in my truck and every now and then ill pull it out while feeding cows to shot a deer.

Here in Texas the deer and cows are always together. I can only assume the deer in your area are not use to the cows. Here they are. Ive seen cows and deer in the same wheat field before.