No need to blanch anything for feeders... any heat destroys vitamins, proteins and other ingredients. Freezing should be done as fast as possible for mildest procedure. The slower e.g. vegetables freeze, the bigger the ice crystals become and destroy food structure. I would not recommend chopping up food before freezing, cause chopped food offers a multiply enlarged surface for bacteria to grow. Remember freezing does not prevent spoilage, it just slows down.