<P> Bull rings are usually about 3 to 5 inches (8 to 13 cm) in diameter, depending on the size of the bull . Bull rings are commonly made from aluminium, stainless steel or copper, in the form of a pair of hinged semicircles, held closed by a small brass bolt whose head is broken off during installation . If a ring needs to be removed (for example, if the bull has grown out of it), it is cut or unscrewed . </P> <P> The ring is normally placed on the bull between 9 and 12 months of age . It is usually done by a veterinarian, who pierces the septum with a scalpel or punch . Self - piercing rings (with sharp ends designed to be pressed through the septum and then pulled together with a screw) have been available for many years; these are also usually installed by a veterinarian rather than the farmer . </P> <P> Calf - weaning nose rings or nosebands provide an alternative to separating calves from their mothers during the weaning period . They have plastic spikes which are uncomfortable for the cow, causing her to reject the calf's efforts at suckling . Weaning nose rings are also available for sheep and goats . These nose rings (usually made of plastic) clip onto the nose without piercing it, and are reusable . </P> <P> Self - locking or spring - closing show - lead nose rings, also called "bulldogs" or nose grips, are removable rings that do not require the nose to be pierced . They are often used on steers and cows, along with a halter, at agricultural shows, or when handling cattle for examination, marking or treatment . They stay shut until released, and usually have a loop for the attachment of a cord or lead rope . They give similar control to a bull ring without the need for permanent attachment . </P>

How to put ring in pig's nose