Dr. Judith L. Mulholland

Many people believe that certain breeds do not founder. All breeds, including thoroughbreds, founder, and I have seen racehorses in paddocks, yearlings being prepared for the sales, and racehorses in full work develop laminitis (founder).

I believed for some time that obesity did not cause laminitis. I now understand that laminitis can be caused by metabolic (hormonal) changes due to obesity, that make ponies and horses much more sensitive to changes in diet due to insulin resistance. This is the most important issue related to obesity and laminitis because it is an unseen cause of the disease coming from within the animal, not its direct environment, and helps to explain so many cases of laminitis of formerly unknown cause.

Toxins in the body are usually removed by the liver - whatever their source. When an animal is obese, much of the liver tissue is occupied by fat deposits, reducing liver function, prolonging the toxic effects e.g., from grass/grain overload. Overweight ponies have a greater load on the feet and are more likely to live in the environment (e.g., a paddock), where they are at risk of laminitis. However, other factors are always involved. Therefore, when someone tells you to starve your animal or it will get laminitis, obesity is one of the risk factors, but hyperlipemia from negative energy balance (not enough energy in the diet) is another, and therefore sensible weight loss may help to reduce the effects if the other risk factors in the animals environment are also rectified.

When founder/laminitis is finally diagnosed in cases where the horse has been happily grazing in the paddock for months without any problem, people often say, "I had wondered if he was okay? The horse has become stiff and less active lately". What they were noticing was the slow onset of laminitis, usually after a period of wet weather, followed by warm days and grass growth. It can take weeks before the horse is lame enough to be checked by a Vet.

Some ponies founder if let out onto grass for even half an hour, winter or summer, indicating other health problems. These include metabolic and hormonal problems such as Cushings disease, diabetes, insulin resistance or thyroid gland problems. Obesity effects metabolism and regulation of blood glucose e.g., insulin resistance problems. Mineral deficiency affects the whole system and may be subtle to the untrained eye, and imbalanced gut flora may have no obvious symptoms but predisposes to digestive upset. In many cases, tolerance for grass and grain improves significantly when the underlying problems are treated. This also involves treatment of an unhealthy paddock, not just the horse.

Laminitis, to some degree, can happen "every day". The only true preventive is to lock the animal away from the cause until the underlying problems are identified and treated. This may mean an almost permanent removal from grazing for severely affected animals. When the horse is progressing well after one bout of laminitis, it often succumbs to a second or even third because the owners reintroduce grazing. This is killing with kindness! Every laminitic episode shortens the horses life by increasing the rate at which the animal will be permanently lame. Some horses and ponies are very sensitive to the carbohydrate (starch) in grain, or rapidly growing grass (soluble sugars). Very small increases will trigger a laminitic episode - Refer to Genetics, Body Type and Laminitis above. The same effect can be produced in other horses by giving large amounts of grain or grass to animals that are not used to it. Obese equines are at greater risk.

• Beware of rapidly dieting very fat or pregnant equines, as they may develop hyperlipidemia which may be more serious than the original laminitis. Weight loss or gain should be steady. Do not starve a laminitic animal. Feed low carbohydrate, fibrous (seedless hay), and nutritionally balanced food. Refer to The Laminitis Diet for more information.