If you kept the feed dry and in a well aired area it should be OK. If it was exposed to high humidity/dampness it may be moldy. How does it smell? Does it smell moldy or like hay? If it was exposed to high temperatures there will be a loss of vitamins and the fat may have gone rancid. An example would be the taste of peanuts that you left around for a while.

Did the deer feed on the pellets last year?

Dan O.