Bully sticks are a kind of dried-meat dog treat made from the flesh of a bull's penis. The muscle in the bull penis is very fibrous, and when sectioned, cleaned, and sun-dried, it becomes very hard and a suitable treat for teething dogs. .
Bully sticks are also known as "pizzles," an archaic English term for an animal penis. For dog treats, the pizzle may be cut into short chunks for easier chewing, or left uncut as a long, twisted stick. The process for making pizzles is dissimilar to the drying process for beef jerky in that pizzles are unsalted and do not utilize marinades to aid the aging process. The lack of chemical preservatives can lead to bacterial growth, particularly E. coli.