The gullet of a saddle is the channel that runs down the center of the underside of a saddle, in between the panels. The gullet bridges the horse’s spine so it is an important part of the saddle design. If the gullet is narrow, it can pinch the muscles on either side of the spine which ultimately will make your horse’s back stiff or sore. The horse’s spine is where the nerves of the back are located; to prevent the saddle from impinging on these nerves, the gullet needs to be wide enough to distribute the weight of the rider on the horse’s muscle.
Many people confuse Tree Size with Gullet Width. Tree is a completely different measurement: it refers to the distance between the bottom of the points of the tree. This measurement is either described in centimeters or as medium, medium/wide, etc. Please note that these excellent descriptive photos are from: How to Measure an English Saddle. The rest of the photos are mine, but these just illustrated the concepts more clearly.
I think that part of the confusion between tree size and gullet width is due to the popularity of the Wintec saddles with interchangeable gullets. The concept promotes the idea that by interchanging the “gullets” you can adjust a saddle from a narrow tree size to an extra wide. And you can. But the Wintec gullets are inserted into the front of the saddle and they change the angle of the tree — and may change the front part of the gullet slightly. If you look at the photo on the left, imagine that the inverted “V” is either narrower or wider. In some saddles, the saddle gullet is wider at the pommel end and narrows over the length of the saddle.
In fact, there are saddles where the gullet becomes very narrow indeed. In the photo above are two saddles: an old Hermes close contact saddle and a recent model County cross country saddle (the Extreme). They are both medium trees, according to their manufacturers, but they are different sizes. The Hermes is a 16.5″ and the County is an 18″.
As you can see, on the Hermes saddle, the gullet narrows significantly as it approaches the back of the saddle. In fact, you can barely fit two fingers in the gullet of the Hermes. A very narrow gullet will pinch and put pressure on the sides of the spine, which will cause back soreness.
Very narrow gullets are more often found in older saddles. I’ve heard it said they were designed to fit “A-framed” thoroughbreds and are not as suitable for the warmbloods that many people ride today.
A saddle that sits on the horse’s spine/ligaments will be painful and will likely result in tightened back muscles and a hollow back. Over the long term it can cause permanent damage to the nerves and ligaments.
In comparison, the County has a nice wide gullet. In fact, you can comfortably fit three fingers in the gullet. I’ve read that the “three-finger” rule is a good starting point for gullet width, although each horse is different.
A wider gullet protects your horse’s spine. And a gullet that is of a consistent width protects the length of your horse’s back. After all, your horse’s back does not get narrower as it moves toward the tail, so neither should your saddle gullet.
A wide enough gullet which helps support the rider’s weight, encourages your horse to lift its back and engage its abdominal muscles — exactly what you want them to do.
The implications of this difference come when you look at the saddle on a horse. The model here is my 17-year-old Trakehner gelding, Kronefurst.
Given that narrow gullets can impinge on a horse’s spine, why do manufacturers make them this way? As mentioned above, narrow gullets and ones that get narrower toward the back are more often found on older saddles. In addition to those saddles being made to fit the horses we rode twenty or thirty years ago, another rationale is that it improves rider comfort. Many people like riding in a saddle with a narrow “twist” and some saddle manufacturers simply bring the panels closer together toward the back of the saddle to accomplish this. However, it’s not nearly so comfortable for your horse!
Can a gullet be too wide? Yes, if it reduces the size of the panels to the point where they can no longer adequately distribute the rider’s weight. This is fairly unusual; it is more typical for gullets to be too narrow.
In Schleese’s saddle fitting videos, they include one that talks about how to determine the right gullet fit for YOUR horse.