Bully sticks, also known as pizzles, are made from dried sections of bull penis that have been stretched and twisted to form long hard sticks. They may be cut into smaller treats or left as-is for use by large dogs. Sometimes smoke is added during processing to flavor them.
Bully sticks are manufactured in a process similar to making beef jerky. Both pizzles and jerky are made by drying animal flesh to make it tough and less susceptible to rot. However, the drying method for making bull penis into bully sticks does not technically include any sort of cooking, and harmful bacteria can remain inside the flesh even after it has been thoroughly processed. The process also renders bully sticks very nutrient dense.