This page is a work in progress, I will be adding to it as I have time.

There are many hoof ailments out there. Most of them can be avoided with regular hoof care and a balanced diet.

CRACKS
Horses develop a variety of cracks depending on the issue he is dealing with. Most can be avoided with regular, balanced trimming. Cracks can be caused by imbalance in the hoof, which can come about from an irregular trimming cycle (when hooves are neglected they can often grow out unbalanced or begin to break apart and split as they become overgrown). Conformational abnormalities can also lead to imbalances, this lack of balance can cause uneven pressures and cause cracks.
Using a farrier that does not properly balance your horses hooves can also cause cracks for the same reason.
Poor diet and lack of balanced nutrition or vitamins can also cause cracks, some diet issues are discussed below.

DIET

It is important that your horse is getting the vitamins and minerals that he needs to grow a healthy hoof. If you horse has soft feet that seem to break apart easy no matter what, or has a constant string of abscesses or white line issues, I would recommend looking at his diet and having his pasture tested.
Vitamins such as biotin, selenium with vitamin E, Vitamin C, calcium, copper and zinc as well as many others are all vital to healthy hoof growth. Vitamins are best gotten from the pasture that your horse is on and the hay he heats, because these are the things he is constantly taking in.
There are a variety of hoof supplements out there that can help. I would recommend testing to see what your horse needs or getting a good "multivitamin" type of supplement. I personally like and have used Source Hoof.
Having regular dental care is also important so that he can chew his food well and be able to absorb the nutrients.

Metabolic Disorders

I see so many horses that could be helped if their owners would put them on a dry lot area or use a grazing muzzle. Metabolic disorders stem from constant  overgrazing or overfeeding. This is dependent on the type of horse or pony, as what one might think is not a lot of food can be a huge amount to certain horses. Most any breed of horse or pony bred to live in a range or dry area will tend to readily absorb food in a fashion similar to a high powered vacuum cleaner. These ponies and horses are the ones said to "get fat from breathing" or to be "air ferns" meaning very little food can make them very fat. You must be careful they get the "right" food, meaning feeding a low-starch feed, dry-lotting or having them wear a grazing muzzle. Pre-soaking hay may be helpful.
Ignoring the signs of Metabolic issues can result in serious chronic diseases and founder.
You can look at your horse and see if he is at risk.
Do you have a hard time feeling any ribs when you run your hand along his side? You should be able to feel, but not see, them when you press your fingers against him.
Does your horse have an unusually cresty neck?
Does your horse have "fat pads"? There are several crucial zones to be aware for fat pads that indicate a precursor to metabolic issues.
this image was taken from: http://peneq.com/a-healthy-weight-how-to-score-your-horse/

If your horse seems to have excessive amounts of fat in a sort of "pad" or "pocket" in those areas seriously consider a diet overhaul or he will continue to be at a great risk for diseases such as Cushings and Equine Metabolic Syndrome.

These issues, while extremely negative for the horse's entire well-being, also effect the feet. It is impossible to grow healthy feet when the horse is ill. Strange growth rings appear on feet of metabolically stressed and foundered horses. Time, patience, proper diet, and regular hoof care will help grow healthy feet back.