I love lambs -- they're adorable! -- and I have great respect for lungs. But never did I think that I would mention the two things in the same sentence as often as I do... 

At School For The Dogs, we use dehydrated lamb lung as treats all day, every day. The dogs love lamb lung, so we do too. LL (as we fondly refer to it at the training studio) is great for training because it breaks up very easily into tiny bits without crumbling, and it isn't at all greasy, which means it's not the worst thing to have to have shoved in your palm, or lining your pockets. Our house-brand, sourced from New Zealand, is very thinly sliced, making it extra easy to break. It's a great source of lean protein, and contains no preservatives, flavorings, or additives of any kind. It's also a good treat for dogs who have allergies, since it contains a single protein -- a single ingredient!

Little known fact: Cats love it too!