by Dr. John Sylvester of Mars Horsecare, US.
Laminitis and Founder are two words that are often used interchangeably, but do not actually mean the same thing. Laminitis refers to an inflammation of the laminar tissue in the hoof and tissue that hold the coffin bone in place. Founder refers to an actual rotation of the coffin bone within the hoof. Laminitis does not necessarily lead to founder, but it can if it’s not treated quickly. There are several situations that can lead to laminitis or founder, including trauma, concussion, drugs, toxemia, and a diet high in soluble carbohydrates (starches and sugars). Most of these can be managed with some forethought and attention to detail.
Nutritional laminitis is linked to the amount of soluble carbohydrates in a horse’s feed. Bouts can be caused by an over consumption of grain, either in one sitting, or by feeding large grain meals. A rule of thumb for an average 1000-pound horse is to feed no more than (4) pounds of a standard mixed grain or pellet at one time. Straight corn should be fed in even smaller amounts.
Laminitis can also be caused by an over consumption of rich spring pasture. Grasses or legumes, such as clover or alfalfa, are growing rapidly in the springtime. These plants can be very high in starches and sugars. If the horse’s digestive system is not accustomed to a high level of starch it can cause digestive problems that can lead to laminitis. Therefore, it is recommended that the horse be introduced to young pastures slowly. They should only be turned out for one to two hours per day to begin and the gradually the amount of grazing time can be extended. This may mean that the horse may need to be taken off of the pasture used in winter and kept in a stall, or a dry lot until adapted to the new grass in the pasture.
Fructans are a type of soluble carbohydrate that is not digested in the small intestine. Fructan sugar accumulation can reach high levels in cool-season grasses such as: orchard grass, timothy, and fescue. Research suggests that when fructans are consumed they reach the bacteria in the cecum and are fermented into lactic acid, which can lead to laminitis and founder. Fructan levels tend to rise during the spring and fall, which are times when the nights are cool, the days are warm, and the grasses are growing rapidly. Horses prone to laminitis should be kept off such pastures from mid-morning until late afternoon.
If fructan levels are too high, you may need to restrict your horse’s access to pasture – but it may be difficult to take a horse off of a pasture entirely. If you can at least limit the horse to a smaller section, particularly one with little grass, it is better then doing nothing. Another alternative is to use a grazing muzzle to limit the amount of pasture the horse can consume in one day, which may keep the horse from becoming laminitic. It is also helpful to keep hay where the horse has access to it, particularly if the pasture is lush.
When should you be concerned about Laminitis? Obese horses and ponies, horses that have foundered before, and horses with Cushing’s, are more prone to laminitis. You should especially be concerned about the possibility of laminitis if your horse is overweight or obese. If his body condition score is 6 or higher, limit the amount of pasture using the methods discussed earlier. Another condition that must be strictly managed involves the Cushing’s horse. Horses with Cushing’s syndrome are very susceptible to Laminitis when the starches in their diets change rapidly, or are very high. While a horse may be very thin, this is not a reason to give them a lot of high-starch grains. Minimizing starch intake is vital for health and soundness. Be sure to avoid exposure to rapidly growing pasture during the early spring and fall seasons. Feed a low-starch/high-fat grain mix or pellet.
Once your pasture is out of the rapid-growth season (April to June in the spring, and for a short time during the fall), most horses can be left on the pasture full-time. It is never recommended to leave a horse out the pasture for a long period of time if they’ve recently been confined to a stall - these horses can eat considerable amounts of pasture quickly and must be introduced to the pasture slowly or utilize a grazing muzzle.
If your horse is showing signs of laminitis – Warm hooves, bounding pulses in his lower limbs, walking “on eggshells” so to speak, or leaning backward in an attempt to keep weight off the front feet – You should call your veterinarian immediately. Early treatment can stop or at least retard the progress of laminitis and may allow the horse to recover completely. Your veterinarian will provide you with a suitable treatment program.