The sky is so blue! The air is so crisp! But when you bring your horse in from the pasture, he balks and shuffles his feet. Veterinarians call it "walking on eggshells." He seems to say "ouch!" with each tentative step.
The last time your horse did this was in April a few years ago, when he ate too much spring grass. But this can't be laminitis. It's fall. Laminitis is a springtime disease. Or is it?
When fall comes, pastures are often buffeted by warm days and cool nights, as well as rain. Pastures enjoy a dark-green flush when early frosts come. Fall conditions create a flurry of photosynthesis that might be akin to the squirrels gathering nuts: The grass surges with energy as though to ensure its survival.
For horses that graze on fall pasture, increased photosynthesis means the sugary grass tastes sweeter. They may graze the same number of hours daily in fall as in summer, but are taking in more carbohydrates. This is dangerous for horses predisposed to laminitis.
Horses may've been ridden often in the summer, but as activities slack off in the fall months, fitness levels plummet. Mares and stallions may experience reproductive hormone surges. As flies die off and cool weather sets in, horses seem to have more energy and a brighter attitude.
In fall, many horses also receive vaccinations and deworming medications, and/or are hauled long distances for season-end shows or sales. Many owners start to increase grain rations as the weather cools. Blankets and rugs come out of storage.
Any of these factors may affect a horse's metabolism and stress levels — and increase his grass laminitis risk.
What is Laminitis?
Laminitis is the most serious disease of the equine foot and causes pathological changes in anatomy that lead to long-lasting, crippling changes in function (termed chronic laminitis or founder). It's the second biggest killer of horses after colic.
A horse has laminitis when the foot's lamina, the connecting fibers between hoof wall and bone, suddenly fail. Without the bone properly attached to the inside of the hoof, the horse's weight and the forces of locomotion drive the bone down into the hoof capsule. Important arteries and veins are sheared and crushed, and the blood delivery system to the coronet and sole is damaged. This results in unrelenting foot pain and lameness.
Laminitis' clinical signs, the extent and severity of the condition and the response to therapy vary unpredictably, making treatment and accurate prognosis difficult. Severe damage to the hoof can occur within a few hours, and the severity and extent of this initial damage is the single most important factor influencing the final outcome.
Grass-Laminitis Risk Factors
All horses are at risk for grass laminitis, but some factors tend to increase that risk. Here's a rundown.
- Metabolic disorders. Grass laminitis is especially problematic for ponies and easy keepers (horses that tend to keep on weight). Easy keepers may have complex problems with their metabolism called Equine Metabolic Syndrome; they tend to be heavier than normal, regardless of how little grain they are fed. They may not look fat at first glance; many have pads of fat on their shoulders and at the base of the tail and their necks have overdeveloped crests. These horses may be sensitive to the supercharged nutrients in spring and autumn grasses.
- Obesity. "Obesity is the single greatest cause of laminitis in pleasure horses," says laminitis-prevention pioneer Donald Walsh, DVM, of Homestead Equine Hospital in Pacific, Missouri. "Other risk factors take on a greater importance when they show up in a horse that's obese, as well. Based on my experience observing laminitic horses over the past 36 years in veterinary practice, I believe that obesity leads to the development of weakened laminae, weakened supporting structures of the foot, and changes in the growth pattern of the feet."
- Springtime bouts. Most horses that suffer from grass laminitis seem to have bouts of it in the springtime when the pastures come back to life after a winter of dormancy. In reality, some veterinarians think that the spring grass is just the icing on the laminitis cake that pushes the horse's system into the red zone. It's the trigger that causes an at-risk horse to become sick. Once a horse has had laminitis, the disease often strikes again
- Classic factors. The classic causes of laminitis compound the risk for grass laminitis, says Dr. Walsh. These include grain overload, retained placenta in mares, drug reactions, hyperthermia, black-walnut toxicity, systemically ill horses or horses with high fevers, pregnancy disorders and high stress. While some horses have only mild bouts of grass laminitis, it may be a much more serious problem for a horse with other health problems.
10 Grass-Laminitis-Prevention Tips
1. Know your horse's normal body-condition score. "Obesity is the single greatest cause of laminitis in pleasure horses," says laminitis-prevention pioneer Donald Walsh, DVM, of Homestead Equine Hospital in Pacific, Missouri.
2. Keep your horse active.
3. Don't increase your horse's grain ration just because the air is crisp.
4. Analyze the hay. Best is hay with a less than 10 percent nonstructural carbohydrate (NSC) level. Soaking hay in water before feeding reduces its sugar content.
5. Subdivide large pastures into smaller lots. Keep a diary of rainy and sunny days, and notice night and day temperatures: Cool nights and warm sunny days usually create the biggest energy surges in pasture grass.
6. Use a grazing muzzle on your horse for prolonged turnout.
7. Fence off an area and turn it into a dry lot. Prevent grass growth with layers of sand, stone dust or wood chips. Even sparse grass can be dangerous to an at-risk horse.
8. Know your horse's foot condition. Ask your farrier how the white line looks and whether your horse has founder rings on his feet.
9. Look at your horse's medical history, and keep a diary. Does your horse have intermittent mild lameness in the spring and fall? Do you see a pattern of when he's lame? Does the lameness correlate to changes in grazing times or a new load of hay? Mild laminitis may not be noticeable, but you can sometimes tell when your horse is "off."
10. Be prepared. Plan what to do if your horse becomes lame. Boots with supportive pads are a good investment. Make sure your farrier trims or shoes your horse with laminitis-prevention in mind, and on a regular schedule.
Here are six grass-laminitis warning signs.
1. Your horse may assume an unusual stance, with his front legs stretched out.
2. Your horse may walk gingerly, or rock back and forth, as though trying to get his weight off one foot, then the next.
3. On the lead line, your horse may walk straight ahead, but balk when asked to turn.
4. Your horse may lie down more often than usual.
5. You may notice a change in the growth pattern of your horse's feet. His heels may grow faster than the toes, and growth rings may look curved instead of symmetrical. A ridged hoof wall, marked with raised "fever rings" can indicate a mild laminitic response or change in hoof-growth pattern in the past few months. The white line on the foot bottom may be stretched.
6. You may feel a strong pulse at the back of your horse's fetlock and/or an abnormally warm hoof wall; these are danger signs.
If you believe that your horse is suffering from laminitis, don't panic. Slowly and carefully move him to a stall. Feed hay, but not grain or sugar-rich carrots and apples. Call both your veterinarian and your farrier.
Laminitis-prevention pioneer Donald Walsh, DVM, recommends standing all four of your horse's feet in deep ice water for the first 24 to 48 hours.
Don't medicate your horse until he's been seen by your veterinarian. Your vet needs to make an objective judgment about your horse's level of pain and the severity of lameness.
Most veterinarians treat every horse as an individual. Your vet will likely draw up a diet and medication plan for you, and work on a shoeing or trimming plan with your farrier or a specialist.
Discuss other medications your horse may be taking, as well as any oral supplements, with your veterinarian.
Animal Health Foundation
Australian Equine Laminitis Research Unit
Katy Watts Rocky Mountain Research and Consulting Inc.
Fran Jurga is editor and publisher of the Gloucester, Massachusetts-based Hoofcare & Lameness: The Journal of Equine Foot Science, and its informational website, www.hoofcare.com.