It' s been my experience here in Sw Iowa that when cows move into a pasture or grain field, the deer move out. I' ve seen crop fields harvested and the deer move in right away and start gleaning the leftovers. Then the landowners would move their cattle on there to do the same thing. Once the cattle moved in the deer would go feed elsewhere. Now elsewhere might only be on the other side of the fence but thet don' t seem to ever be in the same field as cattle. Just my observations.