Which conformation flaw is known to affect the gait of the horse?

Splay foot, which refers to a condition where a horse's hooves point outward rather than straight ahead, can significantly impact the horse's gait. This conformation flaw can cause uneven weight distribution and lead to various movement issues such as instability or unevenness in stride. It can result in the horse struggling to achieve a balanced gait, which is crucial for activities such as riding or therapeutic riding.

In contrast, while short legs, long back, and narrow chest can have effects on overall performance and health, they do not directly influence the biomechanics of the horse's gait to the extent that splay foot does. For instance, short legs might affect stride length and jumping ability but are less likely to cause immediate gait issues compared to the way splay foot alters hoof placement and movement efficiency. Thus, splay foot is considered the conformation flaw most directly related to affecting the horse's gait.