There is a wide variety of “normal” backs with horses, but ultimately it should be strong, of adequate length and in proportion to the rest of the horse. A horse with a long back is more prone to muscular injuries and can find it harder to track up and connect their hindquarters to their forehand. A short back is more at risk of kissing spines, and the horse may be prone to over reaching or forging.
In addition to the length of the back of the horse you should also look at the shape of it and it`s muscular development. The ideal back has a slight dip behind the wither, along the thoracic vertebrae, rising to the croup; in older horses or those with “sway backs” this dip is pronounced. Think of it like when we arch our backs; the horse`s spine is weaker and it is less able to carry weight. A horse in poor condition may look like it has a sway back due to a lack of muscle. A roach back is when the spine curves up along the thoracic and lumbar vertebrae; these horses struggle to flex and often have stiff gaits.
Sometimes obese horses look like they have stronger, better backs, because the fat gives the illusion of muscle development. Within an obese horse, with a flat broad back, there is often “mutton withers”, which is a poorly defined, flat wither which makes saddle fitting difficult.
The rib cage of the horse should be well sprung; the horse shouldn`t be slab sided, as seen in many Thoroughbreds, as this makes it difficult for the rider to put their leg on and there is less room for the lungs to expand. If the rib cage is too round and well-sprung it can affect the upper arm and shoulder movement, but it does give a lot of room for the lungs to expand. Another conformational point of the ribs and barrel is “herring gutted”. This is when there is a sharp rise from the girth to the stifle, giving the horse a greyhound appearance. This appears in stressed horses, such as three day eventers at the end of the competition, in undernourished horses, and in those who don`t engage their hindquarters or use their abdominal muscles. This affects their stamina, stride length, jumping ability, as well as pre-disposing them to back problems.
Growing up in the depths of Wales I`d never heard of Kissing Spines until I spread my wings and moved to England, where I heard and saw numerous cases, or just horses with suspected KS. Horse and Hound recently did an interesting article explaining it – http://www.horseandhound.co.uk/horse-care/vet-advice/explaining-kissing-spines/
It raises the question though, are Thoroughbreds and Warmbloods more susceptible to Kissing Spines than the Native, cobbier breeds? Or is this because the work, the level of schooling and jumping performed or expected by the finer horses make them more prone to developing problems because of the higher demand. Or is it a cause of the inbreeding, or breeding for certain traits? I`ve also noticed, in my larger view of the world, that so many horses have bad backs. Not a problem, it appears, in Wales. Again, is this the level of work, conformation, or the type of rider?
The increase in kissing spines cases could also be due to the “quick fix” riding techniques, as people moved away from classical training, and aimed for the looking pretty, quick fix, route with handy riding and training aids? Hopefully now, since Britains success in the Olympics riders of all abilities will start to revert to the classical techniques and we see a decrease in the number of kissing spines problems.
I remain, however, a firm fan of the Native and Cob horses because they`re so much more robust!