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The ribs of mammals, including the horse, serve one primary purpose: to protect the vital organs of the thoracic cavity, most notably the heart and lungs. Each rib is attached to a thoracic vertebrae, so horses generally have 18 pairs of ribs, corresponding to their 18 thoracic vertebrae. Occasionally, a 19th rib may be present on one or both sides of the vertebral column, but these ribs are usually partially formed or misshapen. The interval between any two ribs is called the intercostal space.

Ribs are not all the same length, width, or shape—some are short, others are long; some wide, others narrow; some have greater curvature to their shafts. Rib length increases from the first rib, which lies just behind the point of the shoulder, to the eighth or ninth, and then diminishes again. The last rib is the shortest and most slender, usually.

The ribs of an extremely skinny horse are easy to see and feel. Conversely, the ribs of a horse in moderate body condition—not too thin or too fat—are not visible but easily palpated. A thin layer of fat keeps the ribs from being noticeable in these horses. Obese horses often have so much fat coverage that ribs are difficult, or impossible, to palpate.

Because of the ease in locating and evaluating the ribs and the amount of fat covering them, this anatomical point factors importantly in arriving at an appropriate body condition score.

Developed by Don Henneke, Ph.D., at Texas A&M University in the late 1970s, the traditional body scoring system uses a range of numbers—1 to 9—to describe general body condition, from extreme emaciation (a score of 1) to obesity (a score of 9). Moderate body condition lies in the middle (a score of 5). Some people condition score horses frequently and thus have fine-tuned their evaluation skills; these individuals sometimes assign half scores (3.5 or 7.5, for example) to provide further specificity to their findings.

The ribs offer evaluators with a logical leaping-off point to start a full-body assessment. Some view it this simply: if ribs are visible, the horse is at least a body condition score (BCS) of 4 and maybe lower; if ribs are not visible, the horse is at least a 5 and perhaps higher. Ribs are not the end-all, be-all in body condition scoring, though. Consideration of other anatomical points help horsemen arrive at a final and more concrete score. Other measures of condition include the shape of the neck and how it blends into the shoulder; the structure of the back—is it peaked like the roof of an A-frame house or wide and flat; and the protuberance or fleshiness of the hipbones.

Recording body condition every week or two allows horse owners an opportunity to keep weight fluctuations in check. Jotting down a score and a few quick notes about body condition and diet will help fill in memory gaps if a weight issue arises. It can be as simple as this:

March 20. Buttercup, about a 5 BCS. I can feel the ribs but I can’t see them. No crest, topline has a normal appearance. Eating mostly first-cutting hay and nibbling on new grass. Vitamin/mineral supplement.

Later in the year:

June 15. Buttercup, about a 6+. Ribs are much harder to feel. Getting cresty, back is flatter. Grazing all the time now. Lots of rain, grass good. Vitamin/mineral supplement. Started using grazing muzzle.

Keeping a journal of body weights allows horse owners to recognize changes in their horses’ condition and to adjust diets accordingly. This is particularly important for horses that are not ridden or driven often, as girths, cinches, and surcingles often reveal weight changes in horses ridden or worked frequently.

Do you have a question about body condition score and how to increase or decrease your horse’s weight? Let us help!


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