I have been feeding hay (mostly grass/clover mix - field is spotty on alfalfa) the past 8-9 years more as bait for pics. As a disclaimer, this is on cattle farms, where hay and hay fields are accessible (although we don't really notice any deer activity where the hay is stacked. I usually get a few weeks out of a 50 lb bale so I don't think they are gorging on it. Pure alfalfa probably wouldn't last as long as I think they like it better. A lot of years grass hay will last a long time with a mild winter. This year may be different tho with more snow and colder temps (I put some out a few weeks ago but haven't been back to check on them yet). I haven't noticed any dead deer in the immediate area of where I've fed. I've found a few carcasses in the spring over those years, but I've found them on properties where I've fed and others where I haven't, so I just assume it was other causes.