I've seen Deer walk right past several fields to feed far away from cover. The only answer I can think of is they smell nutrients in the chosen field that they need.
If they aren't eating your crop they are eating something and towards the end of the year, either due to the longer nights or trying to put weight on for winter they feed more.
I once planted winter Rape a little late and figured it needed a boost. I lightly fertilized with K-mag and the Deer went nuts for the stuff.
Deer have a sweet tooth, after the first frost many plants get sweet, basically they produce their own anti freeze.
I taste some of the stuff in my plots. Some varieties of Brassica have a bitter taste. "By definition, if a seed is labeled "canola" it has to have less than 30 micromoles of
glucosinolates and less than 2% of erucic acid." "These natural chemicals most likely contribute to plant defence against pests and
diseases, and impart a characteristic
bitter flavor property of
cruciferous vegetables." I'm not saying this is your issue, just an idea.