My current favorite butchers (ie. nearly the closest shop) sells frozen offal labelled as dog food, but they assure me it is treated with the same standards as the human food. That makes up about 90% of the meat I eat. Yesterday they had a load of chicken giblets at £1.50/Kg. You are hard pressed to get any high quality vegetable protein for that.
Offal is all the guts and organs right?