Which nerve is most commonly damaged in cases of 'sweeny' in draft breed horses?

The suprascapular nerve is most commonly associated with the condition known as 'sweeny' in draft breed horses. This nerve plays a critical role in the innervation of the muscles surrounding the scapula, particularly the supraspinatus and infraspinatus muscles. Damage to the suprascapular nerve leads to atrophy of these muscles, which can result in a characteristic drooping of the shoulder and a noticeable lack of ability to protract the limb, causing the appearance typically described as 'sweeny'.

The condition often arises from trauma or stretching of the nerve, particularly in large or heavy draft horses, which are more prone to such injuries due to their size and the physical demands placed on their bodies. By affecting muscle tone and movement, the damaged suprascapular nerve contributes significantly to the clinical signs associated with sweeny, making it the nerve most commonly implicated in this condition.