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Multiple factors affect the shape of the topline of horses, principally body condition or weight, individual conformation, and age.

The prominence of the spinal column, or backbone, is a key factor in determining body condition score. Horses in low body condition, those in the 1 to 3 range, will typically have a sharp ridge along the topline, from the base of the withers to the peak of the croup. Because of the musculature of the hindquarters, the vertebrae of the croup are sometimes flesh-covered when those of the back and loin region are protuberant, though this is dependent on conformation as well. In severe cases of emaciation, however, individual vertebrae are distinguishable in every region of the spine from the posterior withers to the dock.

As horses reach moderate body condition, the spinal column is no longer visible because more adipose tissue, or fat, is deposited on top of the muscular sheets that surround the vertebral chain. The topline generally appears flat and smooth in moderately fleshed horses due to this fat accumulation.

Weight gain widens the back and further flattens the topline, especially when horses are scored 7 or 8. At this point, fat buildup has usually created a visible and palpable gulley that runs the length of the topline. As a horse moves into the highest category, that signifying extreme obesity and a score of 9, the topline might become subtly wavy as fat accumulates in patches or plaques, especially near the croup.

Conformation extremes change the appearance of a topline. Horses with lordosis or kyphosis—referred to commonly as sway-backed and roach-backed, respectively—typically have significant curvatures in their spine. Both of these conditions may have congenital origins, the basis of which are malformed individual vertebrae or abnormal connections between vertebrae.

Horsemen often believe that the appearance of sway-backed conformation is a sign of age, just as a whitening face or lost teeth might be. Unlike congenital lordosis, acquired sway-back usually results from a lifetime of use, oftentimes in a habitual way that did not support abdominal strength and self-carriage.

Imagine trail or pleasure horses that spend the majority of their “saddle time” stargazing, with heads held in a strained upside-down carriage with concomitant constant, low-level clamping of the back. Years of defensive and anxious posture under saddle or between shafts can change a horse’s topline, as the back muscles tighten, the abdominal musculature weakens, and the back sags. Horses that have experienced years of competent, sympathetic riding that promotes self-carriage are much less likely to become sway-backed as they age.

The topline is just one area of a horse’s body used to assess body condition. Other areas include the neck, shoulder, ribcage, and tailhead. Learn more by downloading the Body Condition Score Chart.

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