I save all the trimmings of sinew and gristle from my deer/antelope/what-have-you. They all go in a crock pot on low with a little water for a low and slow overnight. They go thru the grinder when still warm and back into the crock pot for another low and slow session. Keep adding water so that it is just wet to the surface. When this has cooked down into a mess of hide glue and meat grindings, I spread it out on a cookie sheet and pop it in the fridge.
Once it sets up like meat knox-blox jigglers, they get cut into little chunks for dog treats. I used these and trained my dog voluntarily do dishes for me (ok, she naturally wanted to lick the plates clean) but she will do anything for these goodies. No artificial ingredients, all natural, organic, free range dog treats. Just be careful, introduce slowly to your dog because they may cause farts that will peel the enamel off your teeth and lead to divorce.