Anco Bully Muscle Tubes are made from 100% Beef Aorta - a great choice for dogs in many ways. Beef Aorta is the largest artery leading out of the heart, and is rich in Zinc, Phosphorus and Collagen. These properties in the Beef Aorta are great for keeping dogs joints and bones nice and healthy, whilst also keeping their teeth nice and clean! These are a great, tasty chew the dog is sure to love.