In reading this thread I was curious about something I was told a while ago. A friend of mine said he was having issues with deer eating all of his plants. He said he was given advice to utilize dried cow's blood. To just sprinkle it onto the grass and it would deter the deer from coming onto his property. He said it worked well for him. He said a side benefit was that it fertilized his lawn, or at least made the grass very dark green in the process.
My question is, does this really work? If so, how long can you expect it to last? And lastly, is there any known reason for why this works?