A girth, sometimes called a cinch (Western US), is a piece of equipment used to keep the saddle in place on a horse or other animal. It encircles the barrel of the equine, and attaches to the billets (girth tabs) of the saddle on either side. Girths are used on English-type saddles, while western saddles uses a girth equivalent called a cinch.
Although a girth is often enough to keep a well-fitting saddle in place, other pieces of equipment are also used in the jumping or speed sports, such as polo, eventing, show jumping, and fox hunting. These include breastplates, breastgirths, breastcollars, and overgirths (surcingles).
Studies have shown that, although girths may restrict the movement of the ribcage in the horse, they have no effect on the horse's ability to take in air.
Several types of girth are shaped to allow ample room for the elbows. The Balding style is a flat piece of leather cut into three strips which are crossed and folded in the center, and the Atherstone style is a shaped piece of baghide with a roughly 1.5” wide strip of stronger leather running along the center. A variation on this is the overlay girth, in which the piece of leather in the center is the same curved shape as the girth. This overlay is often stitched in a decorative design.
Unshaped girths are commonly made of flat, heavy cotton, or padded cotton with nylon webbing reinforcement, or out of leather as in the tri-fold or three fold girth, popular among sidesaddle riders and traditional foxhunters.
Fleece girth covers are often used on sensitive horses to protect the barrel of the horse, and some styles of girth come with attached or removable sheepskin liners that perform the same function.
A dressage girth, or Lonsdale girth, is shorter than the usual girths used on other saddles. This is because the dressage saddle has longer billets, to keep the buckles out from under the rider's leg, and so a shorter girth may be used. Dressage girths can be made of all the materials, and in all the styles, mentioned before, and also can be made entirely of very strong elastic.
An overgirth or surcingle is often used in addition to a regular leather girth. Made of leather or nylon with an elastic insert (for racing), the overgirth completely encircles the horse around belly and the saddle's seat. It is used by stockmen, eventers, polo players, in flat racing, and by steeplechase jockeys to provide more security in holding the saddle in place.
Some girths (those used on jumpers and eventers) have a belly guard (or stud guard), to protect the belly from being stabbed by horseshoe studs as the animal tucks his legs up underneath him over a tall obstacle.
A girth should first and foremost spread pressure evenly over the entire area. If it is too narrow, or if it has a narrow reinforcing strip down its center, it may cause discomfort. It is also best if it has some "give" to it, which makes it more comfortable for the horse. Many riders also choose a girth that allows for extra elbow room, so the horse is not restricted as his leg moves backward.
To measure for a girth, the saddle with a pad should be placed on the horse. A measuring tape is then used to measure from the middle hole of the billet on one side, under the horse's belly, to the middle billet on the other side.
If a girth is slightly too small, a girth extender may be used. A girth extender attaches to the billets of the saddle and lengthens them, so that a shorter girth may be used.
Most jumping saddles have three billets. This not only allows the rider a spare should one break, but can also provide an adjustment option. For horses on which the saddle sits nicely, neither slipping forward or back, the first and third billets should be used. On horses where the saddle slips back, the first and second billets should be used.
The second and third should never be used together, as they are attached to a single piece of webbing to the saddle's tree. Since the first billet is attached to a separate piece of webbing, you can safely combine its use with either of the other two billets.
There are other girthing systems available such as the Adjustable Y system or a similar girthing system. These also provide an adjustment option and have a front girth strap which is connected to the saddle tree point, and a rear girth strap giving it a Y shape and stability.