protein supplement for chickens

Milk is our protein of preference for supplementing chickens (pigs, too).  That's because it's free -- just like our grass, because it is grass.  When there's enough spare milk, we sometimes make dry curd cottage cheese with a high acidity and pack it into mason jars.  We can store this in the 'cool room' (enclosed, unheated porch -- in the summer it would be our 'hot room', as if faces southwest).  No refrigeration is needed.  When we open a jar to add to the chickens' fermented grains, it smells so good we often have a bit ourselves.  Food is everywhere; food is important; food is delicious.