A long neck for a horse is a neck that is much more than 1/3 the length of the horse. Long necks are common, especially in Thoroughbreds, Saddlebreds, and Gaited Horses.
A long neck may make it hard to balance the horse, and the horse may fatigue more quickly as a result of carrying too much weight on its front end.
The muscles of a long neck are more difficult to develop in size and strength. A long neck needs broad withers to support its weight.
Lengthy neck muscles are difficult to develop in size and strength. A long-necked horse needs broad withers to support the weight of head and neck.
It is easier for the horse to fall into the bend of an S-curve than to come through the bridle, which causes the horse to fall onto his inside shoulder. This makes him difficult for the rider to straighten.
The horse with a long neck is best for jumping and speed sports (without quick changes of direction), or for straight line riding, like trail riding.