Fat pads develop over many areas, but the most common locations are behind the shoulder, atop the ribcage, over the loin and croup, and around the sheath. The neck fat pad is the most common, and likely the largest, of the fat pads in the body.  A horse's body fat composition is determined by taking several measurements. These include body weight, body condition score (BCS), and the percentage of body fat. The most common site for measuring body fat is the neck region, because it is easy to access and measure. It is also a good site to measure at regular intervals to determine if your horse is gaining or losing fat. It can be measured with a caliper, which is a very precise tool for measuring the thickness of a horse's neck fat.