Open Range Collagen Bully Sticks are single-source protein treats that provide essential nutrients. vitamins. minerals. and they are very high in chondroitin and glucosamine. Collagen is found below the top layer of skin (two layers below the tough outer layer that is used for leather and upholstery and notably rawhide) and is one of the key elements in connective tissue. Collagen is like a glue that helps to hold things together.