Research News: 07/05

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The Research Is In: Garlic Causes Anemia
Garlic is known to cause anemia in other species, and its safety for horses has been questioned in the past but without much solid information to go on. A study performed at the University of Guelph and published in the American Journal of Veterinary Research confirmed that horses will voluntarily eat enough garlic to result in anemia.

Horses were fed freeze-dried garlic as a supplement in gradually increasing amounts, up to maximum amount that they would voluntarily eat, which was 0.25 grams/kg of body weight (this translates into 4.4 oz. for an 1,100-lb. horse), fed twice daily. The horses were brought up to the maximum over a 41-day period, and feeding continued for an additional 71 days. It was found that intakes over 0.2 g/kg of body weight (3.5 oz. for an 1,100-lb.horse) did cause anemia. After stopping the garlic, the anemia resolved over a five-week period, but damaged red cells and abnormally high MCV (mean cell volume) were still detectable. Intakes of over 3.5 oz. twice a day for 10 weeks was sufficient to damage the red cells.

The safety of smaller amounts over longer time periods remains unknown, but this study found horses to be even more sensitive to garlic effects than dogs. If you feed garlic to your horse, periodic checks for anemia are advisable.

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Dialysis For A Horse
Kidney disease and kidney failure is relatively rare in horses but can occur following a severe tying-up episode, when the muscle pigment myoglobin precipitates out in the kidney, essentially clogging it.?? The resulting kidney failure is usually fatal.??

Interestingly, a case study from Purdue University, appearing in Journal of the American Veterinary Medicine Association, reports success treating severe renal failure after tying-up in a 15-year-old Paso Fino gelding by the use of continuous flow peritoneal dialysis.?? This is a technique of constantly running fluid into the horse’s abdomen, where it will pull out high concentrations of toxins and electrolytes, while allowing the fluid containing these to drain off.?? The horse required over three weeks hospitalization, but within three months was back in normal work with normal kidney function tests.

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Hock Arthritis
The horse’s hock is a complicated joint and contains three rows of small bones.?? Most arthritis problems in the hock involve the lower rows, which respond to joint nutraceuticals and topical care, like neoprene wraps.

However, there’s an unusual painful form involving the talocalcaneal joint, which is the joint between the talus (the uppermost small bone), and calcaneous, which is the large bone that forms the point of the hock.

The problem is difficult to diagnose on examination because while the horse will jog off lame after hock flexion, nerve blocks and local blocks produce variable results. Lateral X-rays show the characteristic changes of arthritis in the joint.??

This type of arthritis is also difficult to treat. In a series of 18 cases reported in the Equine Veterinary Journal, injection of corticosteroids had no effect on the pain.?? Rest and the injection of hyaluronic acid (HA) or polysulphated glycosaminoglycan (PSGAG) were also ineffective.?? Even partial neurectomies didn’t help.??

However, stabilizing/fusing the joint by placing small screws across the joint space improved the lameness in all six cases where the procedure was tried.??The technique was developed by Dr. Smith at the Royal Veterinary College in the United Kingdom.

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OCD Stifle Surgery
A study released in the Equine Veterinary Journal, Smith et al, followed 85 horses that received surgical treatment for bones cysts involving the medial condyle of the femur, a common form of OCD (osteochondrosis dessicans) in the stifle.??Not surprisingly, the strongest influence was from age. Horses under the age of three had a much greater chance of returning to soundness and work (64% vs. 35% for the older horses).

Stifle lameness can be difficult to pinpoint.?? As with any lameness problem, a horse that is “off behind” or “funny behind” needs a full diagnostic workup, including nerve blocks and X-rays or other imaging studies to determine the cause, and the sooner the better.?? If it turns out to be a bone cyst in the stifle, chances of a highly successful outcome from surgical treatment drop after age three.

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Use Those Rest Stops When You Travel
Horses shipped long distances are at risk of developing respiratory infections following shipping. A study performed by the Equine Research Institute of the Japan Racing Association looked at some variables that could influence the degree of airway irritation/inflammation and the negative effects of stress on the immune system.

Using a number of trials with different variables — rest times, cleanliness of trailer, hay vs. pellets — several groups of horses were shipped 1,500 kilometers (932 miles). The study concluded that rest periods longer than the usual 30 minutes every four hours are beneficial in reducing negative effects of shipping stress on the immune system.

In the first study group, horses were shipped either facing forward or facing back and given short rest periods (30 minutes every 4 hours). A third group was shipped facing forward and given longer rests (2 hours every 4 hours). Indicators of inflammation and stress were the lowest in the horses getting the long rest periods. In the next experiment, two groups of horses were rested for 1 hour after every 5 hours of shipping, all shipped facing forward, with the first group having hay suspended in front of them, trailer not cleaned during rests. The group 2 horses were given pellets instead of loose hay and the trailer was cleaned thoroughly at each rest stop. Markers of inflammation were lower in the second group.

Airway irritation can be reduced by thorough cleaning of the trailer at rest stops. Feeding pellets instead of hay may also reduce irritation but may increase risk of choke. Common sense dictates that good ventilation is a must.