Strange behaviour in several Appaloosa horses has sparked one of the most extensive research projects about night blindness in horses ever conducted.
On a cold, moonless winter night several years ago, Sheila Archer tossed a feeding tire over the fence to her Appaloosa horse.
“She came walking very slowly, with her head down almost touching the ground and kind of moving it from side to side really slow, like if you were holding one of those metal detectors trying to find a watch in the sand,” Archer said.
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The horse’s nose eventually found the edge of the tire and it began eating.
“That looked very strange to me because it was very slow and I thought there is no way she would do that unless she just couldn’t see.”
Archer, a Saskatchewan breeder south of Moose Jaw, suspected two of her 12 horses were night blind and brought them to the University of Saskatchewan’s Western College of Veterinary Medicine in Saskatoon.
“The vets at the veterinary college, when I took these horses in, were not expecting to find these horses to be night blind,” Archer said. “It was a real shock because for years and years, these horses have been fooling everyone.”
The world had been disappearing at nightfall for both horses since they were born. Archer said their vision tested less than 10 percent of normal rod function, which are the cells that activate night vision.
Lynne Sandmeyer, an associate professor of veterinary ophthalmology at the college, is studying 30 Appaloosa horses to learn more about congenital stationary night blindness, or CSNB.
Appaloosas are being researched because it is the breed most affected by CSNB, but Sandmeyer said it isn’t the only one.
Little research has been conducted on CSNB to date. The three earliest studies were conducted in the 1970s and another was published in the 1980s.
The research project will look at the incidence of CSNB in Appaloosas while characterizing the disorder’s clinical abnormalities. Part of the study includes conducting electroretinography for an eye exam but the researchers will also investigate different coat patterns on Appaloosas to see if CSNB is more common in certain pattern groups.
Archer is an independent phenotype researcher who co-ordinates the North American Appaloosa Project. She and fellow researchers are searching for the gene that creates the Appaloosa breed, and anecdotal accounts from her work show the coat pattern on the horses could be linked to night blindness.
“Coat patterns that have few or no spots, where the white pattern areas are mainly white, are the ones that breeders reported to me as being what they saw as the horses, in their experiences, to be more likely to be night blind.”
Archer suggested the hypothesis to Sandmeyer and the project was born.
“If I hadn’t come knocking on their door, these mystery Appaloosas would still be stumbling around in the dark with nobody watching them,” Archer said with a laugh.
Sandmeyer said the concept of linking coat patterns to CSNB is new. While there may or may not be a link, it is an idea worth investigating, she added.
Archer suspects two more of her horses are night blind, but they are yet to be tested. She emphasized that Appaloosa owners should not be concerned.
“It (the horse) will use all kinds of other cues around itself, particularly, you know, if it’s in with one or more horses that see normally at night,” Archer said. “You’ll never know because it’ll just travel around with them and use them as their eyes.”
There is no cure for CNSB nor are there visible eye defects. Sandmeyer said owners should take note if their horse spooks easily at night or is more frequently injured at night versus the day.
Research on CSNB will continue until at least next summer, Sandmeyer said.
