by: Anthony Blikslager, DVM, PhD, Dipl. ACVS
September 01 2007, Article
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Recent studies have shown that horses are far more stoic than we had imagined. On the scale of pain tolerance, they are much higher than people. For example, the thrashing colicky horse often needs surgery, and after surgery, pain is very difficult to detect. For years veterinarians have walked by hospitalized horses after colic surgery and figured they were doing fine because they were standing in the back of the stall with no obvious signs of pain. However, recent research has shown these horses are coping with pain and remaining still to minimize movement that might exacerbate the pain.
A classic painful postoperative colic patient will be in the back of the stall, holding his head at withers level, ears out to the side, and paying no attention to his surroundings. Conversely, a normal horse will be at the front of the stall, head and ears up, interested in all the people and horse traffic passing by. This crucial finding was discovered by Debra Sellon, DVM, Dipl. ACVIM, and others while at North Carolina State University. (Sellon is now a professor of equine medicine at Washington State University.)
If these horses are treated like people in the intensive care unit at a human hospital, with constant attention to pain through continuous pain medication administration in small doses more frequently, they feel much better. Horses treated for pain also get better faster and leave the hospital earlier.
On the lameness side, many horses are subtly painful, but the lameness cannot be seen on turf or sand. When these horses are evaluated for failure to perform well, the veterinarian will typically trot them on a hard surface (such as asphalt) and put them on the longe. In this way, foot pain (which is still, by far, the most common cause of lameness) can be detected. In research studies, lameness is best detected with a force plate, where the horses are jogged across a plate that is flat to the ground, and the degree of weight bearing on each foot is detected by electronic sensors in the force plate. This is very helpful because this technique detects very subtle signs of change in weight bearing that might not be visible when jogging on a regular surface, and it can be quantified so that repeat examinations can determine if the lameness is improved.
What does all of this mean for the horse owner? First, for the horse with colic, horse owners are excellent at detecting signs of colic because they notice changes in behavior or routine before signs of pain are apparent. At the first sign of change in behavior, the veterinarian should be called, because this is likely when colic is starting. It is easy to lose track of time, but generally for any horse that does not get better after the first dose of pain medication, something more serious could be going on, and the total time of colic is crucial.
If owners and veterinarians could catch all serious cases of colic within three to four hours, survival rates would go way up, and we would have finally taken steps to dramatically change how many horses are saved.
For the lame horse, the take-home message is that in any horse with a behavioral problem or poor performance, lameness is the first thing your veterinarian should assess. This can best be done by a veterinarian watching as you jog the horse on a hard surface or longe the horse on a small circle. For more subtle cases of lameness, advanced equipment is available to detect lameness, although the best orthopedic veterinarians can see what the force plate sees--subtle lameness that can then be blocked out to determine its origin.
Warboel
