Blue Lupine is a GREAT cool season legume. There are different varieties and you need to make sure you get the forage variety. Any will work but the forage variety that blooms purple is the best. This plant can provide 13 - 18 % protein with a fairly good digestibility rating.
Like hunter 58 said, some arent palatable to deer but the sweet blue lupine variets is like planting iorn clay peas in winter as far as attractivness goes. but make sure to plant with something like oats or wheat as a cover crop to protect frome early over grazing.
When I planted it a few years ago the deer destroyed it in no time. Seems to have the same downfall of planting soybeans,if the plot is not big enough it will take an electric fence to keep them at nay until it gets to browsing point