Bulls are very large and potentially dangerous animals. They are also animals that people sometimes need to interact with. To make bulls easier to control and handle, the bull may be given a nose ring. Like humans and many other animals, bulls have a piece of tissue called a septum in between their nostrils. This tissue is very sensitive so the bull becomes compliant and easily led when a person grabs hold of the ring directly or puts a staff or a piece of rope into the ring. The ring in a bull's nose acts in a manner very similar to the bit on a horse bridle.
The Select Few
Not all bulls have rings in their noses. Rings are usually only put into a bull's nose if it is believed that he will be handled often, such as those animals that will be used for breeding purposes or who will be taken to livestock shows.
The rings placed in a bull's septum are hinged. The bull is given a local anesthetic and then one of two piercing methods is utilised. Either a self-piercing ring is placed into the septum and closed or a sharp piercing nail is used to puncture a hole in the septum and then a ring is placed in the hole.
If a bull is going to have a ring in his nose, the procedure to put it there is usually performed when he is from 6 to 12 months old.
The ring must be made of a material that will not rust and is usually brass. Rings weigh 85 to 170 grams and can be up to 3 inches (7-8cm) in diameter on a very large bull.
The practice of putting rings in a bull's nose in order to lead it is what led to the creation of the oft used idiom about someone being "led around by the nose."