They killed the ones I planted, just like regular soybeans so I personally prefer clover or alfalfa for summer forage.
When I plant soybeans I want "grain" not forage and forage beans usually do not yield as high as regular beans. The other problem is that they stay green right up to first frost which means the turn right smack in the middle of hunting season and they won't touch them for weeks.
I like to plant early maturing soybeans and overseed winter rye into them just as the start to yellow...hard to beat that combination!:way: