Swayback

I was asking my riding partner why her old mare had such a deep dip in her back. She called it "Swayback", and said she wasn't sure what caused it and would like to find out. Someone had told her that it was because her horse was a former broodmare. Could that be true? What does swayback really do anyway? Does it hurt or cause other difficulties?

Here is a really good site that goes into incredible detail about the whole thing.
The Truth about Horse Swaybacks

From what I understand, it usually does not cause a problem when riding. I would just make sure that the saddle fits well and does not cause any pressure points.

Sway back is common in older horses. It can be caused by age, or by too heavy a rider for a long and repeated time. As the horse ages the back naturally sags as the muscle and ligament tone lessens, which cause the back not to be held as it should be. I'm not sure if it causes pain, it probably would if it was a serious dip as there is a chance of kissing spines occuring. Could you get a pic of the horses back? From being a broodmare is can be a reason as the mare has to carry the foal for around 11 months, pretty much every year, if she is a serious broodmare.

Swayback alot of times is losss of muscle or poor quality diet protien... think 12% protien locally mixed feed...

Many times by increasing the QUALITY of protien and exercise some improvement can be seen

I really don't think that higher protein feeds would affect a sway back or prevent it. Horses in general don't need the rich diets they get, in fact, the overfeeding probably contributes more to swayback than lack of any type of protein. Perhaps the feed helps fill in the crevaces with fat, making it appear less swayed,but you can't really fix true lordosis. Some exercises to develop the muscles in the back and abdomen may help, but once it's drooping, droop it does.
Poor saddle fit and obesity (and yes, carrying foals) can do it, but I do think genetics play a major role. Certain breeds are much more likely to develop swayback than others, regardless or feed, workload or having babies.
We have an old Appaloosa gelding with a sway back, and we have to carefully and creatively pad him for the saddle to not "bridge" and cause pressure points on his loin and withers. I actually sewed a pad myself for him to customize the fit. He rides fine, though he has other signs of the previous hard work he did in his younger years (we bought him a year and a half ago) and his legs are showing wear and tear, too. He's starting to get good weight on him now, and his back doesn't appear as swayed, but it is just as much as before. I won't ever let him get fat, though, it's just not good for ANY horse to carry extra weight like that.

My best friend's horse (28 y/o TB) has a very obvious sway back. He's had that since before we knew him (oh... close to 10 years now). She has a special pad she uses under her saddle due to it, but other than that, no problems. She used to show h/j with him and it never caused any issues.

I believe a good diet, protein and exercise helps a sway back. My Arabian has no pain issues, but he is only 3. Looking through his papers a sway back is no where insight. Because he is a pure bred, breeders don't like a sway back and stop breeding if one comes out. Which did happen to his sire. I don't believe a sway back will stay that way forever. I am hopeful there is something to help.