Feeding the Laminitic Horse

Dietary Management is vital in the recovery process and long-term wellness of horses afflicted with laminitis.

By Lori K. Warren, PhD, PAS

The degree of damage to the laminae resulting from a bout of laminitis varies from mild to severe. More severe cases are characterized by a large loss of lamellar attachments, often resulting in coffin bone rotation. In more mild cases, some loss of lamellar attachment is still evident. Such damage persists and can accumulate with successive episodes of laminitis, each time further weakening the link between the hoof wall and the coffin bone. Eventually, enough of the attachments are broken, permitting the coffin bone to rotate. While all episodes of laminitis are serious, the prognosis for the future soundness of the horse is more guarded when coffin bone rotation occurs.

• Feeding mistakes
Although it occurs, breaking into the feed room and gorging on sweet feed is not the most common accidental cause of laminitis. Instead, laminitis is more likely to be the unintended consequence of a feeding mistake. Failing to make adjustments in the quantity of feed given when switching to a new product and failing to provide adequate time to adjust to a new feed are more common mistakes. For example, pellets are typically denser than textured feeds, so a scoop of pellets will weigh more than the same scoop filled with sweet feed. The end result is that the horse gets more feed than it is used to, which can cause digestive upset and laminitis. Formulations between feeds also vary greatly, so be sure to know what’s in the bag and how it compares to your old feed before you give it to your horse.

• Lack of adaptation to lush pasture
Lush pasture, typically found in the spring, is characterized by a high nutrient content. Although high protein is often blamed for causing a horse to founder, this is a myth. Instead, the culprits are high levels of specific carbohydrates. In Florida and much of the southeast, the warm-season grasses (e.g., bahia, bermudagrass) growing in our pastures can contain high levels of starch in the spring. In contrast, the cool-season grasses (e.g., fescue, orchardgrass) present in pastures located in more temperate climates can accumulate fructans. Excessive amounts of starch or fructans both result in the same thing—rapid fermentation in the hindgut, followed by acid formation, microbial death and endotoxin release. For horses that are adapted to the “green up” of pastures in the spring, these carbohydrates generally do not pose a problem. For carbohydrate sensitive horses and those who have been turned out on lush pasture without a period of adaptation, sudden intake of large amounts of starch or fructans can result in laminitis.

• Insulin resistance
Horses that are insulin resistant have a greater risk for developing laminitis than normal horses. Insulin is needed to drive glucose into cells. In an insulin resistant horse, the cells “ignore” insulin resulting in less glucose being taken up by the cell. The laminae in the hoof are obligate glucose users (i.e., they can only use glucose to support their function). Because insulin resistance prevents laminae from taking up glucose, they starve. Other biological events associated with insulin resistance also conspire to increase the risk of laminitis in these horses, including factors that affect blood flow to the hooves.

• Overweight horses
Excess body weight also puts a horse at greater risk of laminitis. Much of this risk stems from the fact that overweight horses are also often insulin resistant. Additional risk comes in the form of mechanical trauma. Carrying around extra body weight puts extra pressure on bones and joints, including those in the hoof. Overweight horses are also more likely to be sedentary, which impacts blood flow up and down the leg.

Although the focus of this article is nutrition, it is not the only cause of laminitis. Laminitis can also result from mechanical trauma (also known as “road founder”). A famous example of mechanical failure of the laminae was Barbaro, who developed laminitis in the limb opposite the one he injured in the Preakness Stakes. Referred to as contralateral limb laminitis, this condition is common in horses who have acquired an injury that requires them to support more of their weight on their healthy limbs. Additional causes of laminitis include bacterial endotoxins associated with a retained placenta, treatment with excessive amounts of corticosteroids (e.g., dexamethasone) and contact with black walnut bedding. Finally, older horses, as well as certain breeds (e.g., ponies) have a greater predisposition towards laminitis.

Despite the cause, the end result is similar—the laminae become inflamed and the attachments between the hoof wall and coffin bone become damaged. An appropriate feeding program is not only important for the recovery of the hoof, but also for preventing reoccurrence.

2) Implement a strategic pasture turnout plan
The carbohydrate levels (either starch or fructans) in pasture forage fluctuate with different seasons, as well as throughout a 24-hour period. In general, starch and fructans are highest in the spring, again in the fall, at times when the grass is “stressed” (e.g., by drought or several cloudy days in a row) and from mid-day through early evening. Pasture turnout should be adjusted to avoid exposure to the higher levels of carbohydrates at these times. In the spring and fall, pasture turnout should be limited to only 1 or 2 hours per day. In the summer and winter, you may be able to extend turnout for another 1 or 2 hours. Regardless of the season, turnout on pasture should be scheduled to occur sometime between one hour after sunset and 10:00 a.m. the next morning when starch and fructan levels are lower. To accommodate your work schedule, you might consider splitting the daily turnout time. For example, turn your horse out for an hour before you go to bed and again for an hour in the morning before you leave for work. A grazing muzzle, which slows the rate of grazing, might also be used to extend the amount of turnout time (only by another hour or so). But beware, veterans to grazing muzzles become very adept at foraging with the device until it eventually no longer slows them down. Finally, horses with a history of laminitis should not have access to pastures that have been over-seeded with winter annuals (e.g., annual ryegrass), due to the potentially high carbohydrate content of these grasses.

3) Select mid-maturity grass hay or grass/legume hay
When not turned out on pasture (which, unfortunately, will be the vast majority of the time), the laminitic horse will need to be confined to a stall or, more preferably, a drylot paddock that contains no grass. This means the nutritional needs of the laminitic horse will be met predominantly with hay; therefore, hay selection is important. Of all the things we feed horses, hays are the lowest in starch (or fructans). That being said, the carbohydrate content of hays can vary dramatically. In general, you should select a mid- to late-maturity grass hay (e.g., Coastal bermudagrass, timothy, orchardgrass). If the horse is thin, you can consider using a grass/legume mix hay (e.g., timothy/alfalfa) or perennial peanut hay. A consistent hay supply is very critical for laminitic horses, so as not to disturb gut function. Therefore, whenever possible, you should purchase hay in quantities that can last you 2 to 3 months and remember to slowly adjust the horse to each new batch of hay. In general, the horse should receive about 2% of his body weight in hay per day (about 20-25 pounds for the average sized horse). This amount may need to be reduced to 1.5-1.75% of body weight if the horse is being fed a commercial feed or is spending some time on pasture.

Another alternative to baled hays are bagged forage feeds. Unlike baled hays, bagged forage feeds offer a guaranteed analysis and are very consistent from bag-to-bag. These chopped forages differ from traditional hays in that they are high-temperature dried rather than sun-cured, thus eliminating weather from playing a role in the time the hay is harvested. Additionally, the mixing of hay types occurs in the mill rather than in the growing process, allowing a more exact mixture and a better variety of hay types. These differences create a much more consistent nutrient profile than traditional hay resulting in a higher margin of safety for your horse, and the need to store large quantities of hay is eliminated.

4) Avoid high-starch feeds (and treats)
Commercial feed products that are cereal grain based should be avoided, due to the high starch content of the grains. Low-starch feeds that are high in digestible fiber (from beet pulp or soybean hulls) or high in fiber and fat (from soybean oil, flaxseed, or rice bran) are more suitable for the laminitic horse. The advantage of a commercial low-starch feed, as opposed to creating your own mixture, is that the feeds are regularly tested to ensure a low starch content. They are also fortified with minerals and vitamins to create a well-balanced ration. If your laminitic horse is overweight, a ration balancer such as Seminole Equalizer should be fed instead of a traditional commercial feed. Ration balancers are a concentrated source of protein, vitamins and minerals, but are low in starch. They are designed to be fed at a rate of 1-2 pounds/day and are tasty enough to be fed alone (which can convince the dieting horse that he is not being cheated).

5) Maintain a healthy body weight
Because excess body weight puts a horse at greater risk for laminitis, you should maintain your horse in moderate body condition. This means you should be able to easily feel individual ribs, but not see them when the horse is standing. If your horse is already overweight, you need to institute a weight loss program. This can be quite a challenge with a laminitic horse, because their ability to exercise may be limited. Nonetheless, exercise is important for weight loss, as well as increasing the circulation within the hoof. As soon as it is permitted by your veterinarian, you should increase the activity level of the horse, even if it is limited to hand-walking for 30 minutes. Commercial feeds and high-calorie treats should be exchanged for ration balancing pellets (see #4 above) and healthier treats, such as hay cubes (but not too many!) Hay should be more stemmy and gradually adjusted downwards to produce weight loss. For example, over the course of one month you might start by feeding hay at 2% of current body weight, drop to 1.5% of current body weight, and then drop to 1.5% of ideal body weight. Until the weight problem is under control, pasture turnout should be avoided.

6) Consider feeding a high-quality hoof supplement
Several nutrients are important for maintaining the health of the hoof. In particular, the B-vitamin biotin and trace minerals such as zinc and copper are needed for proper hoof development. It is unknown if laminitic horses require more of these nutrients than healthy horses. Nonetheless, it may be prudent to include a high quality hoof supplement in the diet of a foundered horse. Research in healthy horses has demonstrated some positive effects on hoof growth when fed 30 mg of biotin per day for at least 6 months. Many hoof supplements also contain zinc and copper, and when coupled with a commercial feed or ration balancing pellet, this should suffice. Your farrier or equine nutritionist may be able to suggest a hoof supplement they have had success with when treating laminitic horses.

Remain Diligent
Laminitis is a serious and dynamic disease. No matter how mild, once damage has occurred in the laminae, the hoof is susceptible to further insult. In addition to working with your veterinarian and farrier to mitigate the damage, consideration of your horse’s diet is vital to recovery and long-term soundness. Many of the changes that have to be made, such as restricting or even eliminating pasture turnout are not fun for the horse and generally mean more work for you. But to avoid the pain and frustration of future episodes, you must stick to a strict dietary plan. Gain control over the diet by limiting grazing to short periods at strategic times. Feed a mid-maturity grass hay or bagged forage, select low-starch feeds or ration balancing pellets, and maintain your horse in a healthy body condition. Consult with an equine nutritionist to create a feeding plan tailored for your horse. Above all, be diligent about the diet of your laminitic horse—he’s depending on you.