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When I was younger I really wanted a Swiss Army knife. I mean really, what kid wouldn’t? It's a knife AND scissors AND a nail file AND tweezers AND there is even a fake plastic toothpick! But as we were taught, with great tools comes great responsibility and Swiss Army knives weren’t just given out on a whim. I can’t remember which birthday it was (9th or 10th) when I finally got the small black Classic SD. But there was a trade off; if I was old enough to receive the coveted multi-tool device that also meant I was old enough to mow the lawn. So to me, mowing the lawn was part of an important rite of passage. I was now deemed responsible enough for not only a small sharp object, but a large, sharper motorized one!  And I enjoyed mowing the lawn, the challenge of getting it started (holding the pull cord with two hands and throwing myself back with all my might), the instant gratification, the smell of fresh cut grass. So when we moved to our current house, that sits on ¼ acre with a small fenced in backyard, I was happy to volunteer for lawn trimming services….until I met our mower.
“Its great,” he said. “It's a real mower.”  “As opposed to a ‘fake’ mower?” I responded. “No, a R-E-E-L mower,” he said with a smile. And then I saw it. It is a modern version of the old fashioned, non-motorized, blades spin in a circle in some scissor like motion, who even knows how the grass gets cut, probably what Tom Sawyer used after he was done white-washing Aunt Polly’s fence, mower. To get it to work, the blades have to be moving fast enough for it to cut the grass, rather than just bend it over, which (without a motor) takes a bit of work, and in such a tiny yard as ours, there’s not a lot of room to get a running start. And if the grass is too long it won’t work, you have to raise the blades, cut it once, lower the blades and cut it again! That is NOT what I consider instant gratification. But as much as I complain and refuse to ever help out in the yard (this also has to do with Chiggers, which we do not have where I grew up and who consider me a delicacy), the reel mower is cheaper (no gas/oil), quieter (he has no excuse not to listen to me while he mows) and is much better for the grass. So that now, just a week into spring, our lawn is thick and lush and needs to be mowed (by someone other than me) at least once a week.

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Rotation of the coffin bone.
And while it is beautiful to look at, fresh, thick lush grass can also be dangerous. Pasture associated laminitis begins to occur after the growth of grass in the spring. In cases of laminitis, the lamina separates between the pedal bone (P3) and the inner hoof wall causing unrelenting pain and characteristic lameness. It is the most serious disease of the equine hoof that leads to devastating loss of function and sometimes loss of the horse. While there are many different conditions that can lead to laminitis, pasture associated laminitis, or “grass founder” can be traced back to the high sugar content of the grass.

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When a horse takes in a large meal containing sugars, they develop a temporary inflammatory condition in the GI tract called “carbohydrate overload.” Starch and sugars are normally digested and absorbed in the stomach and small intestine. The transit time through this portion of the GI tract is about 90 minutes and with a balanced meal, most of the carbohydrates will be absorbed before the feed passes into the cecum and large colon. However, if the meal is too high is sugars, too many sugars enter the small intestine and instead of being properly absorbed, some pass through to the large colon. This leads to a shift in fermentation and acidity of the colon contents and allows dangerous toxins to leak out of the gut into the bloodstream. There is also a large spike in glucose and insulin in the blood stream.  These toxins, inflammatory substances, glucose and insulin reach the hoof and contribute to the formation of laminitis. Prevention of pasture associated laminitis can be as simple as limiting your horses’ access to lush grass.

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However, some horses and ponies are more likely to develop laminitis (have a lower threshold) after consuming a high starch/sugar meal and require more than just limiting turnout time to prevent laminitis. All ponies and some breeds of horses (Warmbloods, Morgans and all “easy keepers”) are genetically predisposed to develop Equine Metabolic Syndrome (EMS). EMS is a disease characterized by obesity, abnormal fat deposition (crest neck, fat around tailhead and above eyes) and insulin resistance (IR). The cells in overweight horses stop responding to insulin and therefore cannot process sugars normally. Because of this, smaller amounts of grass may trigger a laminitic event in these animals. Diagnosis of EMS can be made by clinical signs, body weight and body measurements, and blood testing (insulin and glucose). Once an animal is diagnosed, the condition can be treated with diet, exercise and in some cases, medication.  Dietary recommendations include removing all concentrates (grain) from the diet (or feeding specially formulated low starch feeds), feeding grass hay only (no alfalfa) and limiting access to pasture. Any horse or pony who is obese, considered an “easy keeper,” or who has had a previous laminitic event should be tested for EMS. Equine Cushing’s disease can also lower the threshold for laminitis in horses on pasture. Older horses (>15 years) and horses with clinical signs of Cushing’s (curly haircoat, cresty neck, potbellied appearance, recurrent laminitis) should be tested and appropriately treated. These horses often have IR concurrently and testing for EMS is warranted in all cases of Cushing’s. Horses can be easily treated for Cushing’s disease with daily medication. Like EMS cases, Cushing’s horses should be managed even more carefully on pasture in the spring and summer.

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The following suggestions are just a few things you can do to prevent pasture associated laminitis and keep your horses happy and sound throughout the spring and summer.

  1. Identify the horses and ponies who are at a higher risk of developing laminitis. Test “easy keepers,” geriatric horses and those with a history of laminitis for EMS and/or Cushing’s Disease.
  2. Treat any predisposing condition with diet, exercise and proper medications.
  3. For horses with a lower threshold, consider a zero grazing environment, such as a dry lot (while providing the horse with suitable forage alternatives).
  4. Limit turnout of pasture when grass is lush and when fructans are high.
  5. Turn horses out to pasture when fructan levels are likely to be at their lowest, such as from late night to early morning, removing them from the pasture by mid-morning.
  6. Employ the use of grazing muzzles to allow horses out on pasture but still limit their intake of grass.
  7. Maintain pastures regularly to prevent grass from becoming mature and stemmy (they contain high levels of fructans). 


If you have any questions about pasture associated laminitis and whether your horse is at a higher risk, contact your veterinarian for proper testing and specific recommendations that will work for you.

 
 
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The birds are chirping, daffodils are popping up all over our yard (despite the demolition done to the bulbs this fall courtesy of a runaway stump-grinder) and the sun is shinning! March 20, 2012 marks the first day of spring in the northern hemisphere. So to kick off the new season here is the first installment of a 3-part series of blog posts. While we may all be excited to get back in the saddle and out on the trail, there are a few horse health topics we can’t forget, the darker side of this influx of warm air… And speaking of warm air, I don’t think anyone can argue that its been a mild winter and at least here in Indiana we seem to be moving right onto summer without much of a transition. Forget “In like a lion.” More like “In like an iguana baking in the desert sun!”  Two weekends ago, I wore long-johns to practice and could barely keep my fingers from turning blue. Last Saturday, it was 80 degrees at the kick-off of our first game. That kind of sudden heat really makes you re-evaluate your fitness level.

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But what else does this sudden heat wave bring to life, besides the flowers and grass (and we’ll get to the evils of the spring grass next week)? Bugs! With no more overnight frosts, mosquito season is upon us, and much earlier than normal. Now I know what that means for me, coating myself in OFF and calamine lotion and being driven to insanity by hundreds of itchy bites. But it also has implications for our horses and their mental well-being. Mosquitoes can carry a group of viruses that cause encephalitis, or infection in the brain. These viruses include West Nile Virus (WNV), Eastern Equine Encephalitis (EEE, often called Triple-E) and Western Equine Encephalitis (WEE). There is also a Venezuelan Equine Encephalitis (VEE) but that hasn’t been seen in this country since the 1970s, though some people in southern Texas and Florida consider it a threat.

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Life Cycle of the Viruses:
The virus has a life cycle that mainly involves wild birds. Remember it was a veterinarian who discovered West Nile Virus in crows in New York City back in 1999. Mosquitoes pick up the virus when they feed on an infected bird and then transfer the virus to horses, or humans, when they bite them. These viruses cannot live outside of a host and do not survive in the environment for long and the virus does not exist in high enough levels in the horse’s blood stream to transmit to other mosquitoes, horses or humans. Therefore isolation of infected cases is not required.

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Clinical Signs:
EEE, WEE and WNV all act very similarly in the horse. The virus replicates in lymph nodes and infects the neurons in the brain. Clinical signs can appear anywhere from 2-3 days to as long as 3 weeks after infection. Signs may include: fever, depression, loss of appetite or neurologic signs (incoordination, staggering, hyperexitable, head pressing, leaning on walls, low head carriage, drooping lips/tongue or recumbency). Some horses may have intense puritis, or itchiness. Many horses infected with West Nile Virus will display very fine fasciculations of the muzzle that are often only noticed by seeing their whiskers quiver.  The course of the disease is between 2 to 14 days and fatality rates range from 33% with WNV, to 50% with WEE and up to a staggering 90% with EEE. The only treatment is supportive care (IV fluids/nutrition, anti-inflammatories and corticosteroids).  Horses that are lucky enough to recover may have residual neurologic deficits.


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Prevention: Prevention includes vaccination and mosquito control (removal of stagnant water sources and liberal use of fly-sprays). When given properly (three initial shots 4-6 weeks apart, followed by an annual booster) the vaccines have been shown to be close to 100% effective.  The American Association of Equine Practitioners recommends that the, “annual re-vaccination must be completed prior to vector season in the spring. In animals of high risk or with limited immunity, more frequent vaccination or appropriately timed vaccination is recommended in order to induce protective immunity during periods of likely exposure. In areas where mosquitoes are active year-round, many veterinarians elect to vaccinate horses at 6 month intervals to ensure uniform protection throughout the year, although this practice is not specifically recommended by manufacturers of vaccines.”

So with the early onset of the warm weather, and hatching of billions upon billions of mosquito eggs, I would strongly recommend moving up your horse’s vaccination schedule to cover them against these devastating diseases as soon as you can. The bugs aren’t going to wait to bite your horse just because you’re not due for your spring shots till April! 

And don't forget about Fido and Fluffy! While dogs and cats rarely get these viral encephalidities, mosquitoes carry heartworm disease and the warm weather will bring out other undesirable critters like fleas and ticks which carry a whole set of diseases of their own like tape worms and Lyme Disease. So, if you take a break from your flea/tick/heartworm prevention in the winter, now is the time to start back up again!!


 

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