Thanks to their genetics, Appaloosas, Norikers, and other “leopard spotted” horses are easily recognizable. They traditionally sport flashy spotting patterns classified under a handful of basic categories: spotted blanket, snowcap blanket, full leopard, few spots, and snowflake.

But Austrian researchers recently decided to take that spot research a step further, using high-tech equipment to classify the spotting patterns in better detail. They also aimed to “connect the dots” among the genes themselves, the spots, and additional factors that appear to play a role in the resulting coat constellations.

“The detection that two genes (LP and PATN1) are involved in leopard spotting patterns and the finding that different genotype combinations of these two gene leads to different spotting patterns was a milestone published by Bellone and Holl in 2013 and 2016,” said Thomas Druml, PhD, of the Veterinary University of Vienna Institute of Animal Breeding and Genetics. “Nevertheless, there is a remaining variability in leopard spotted horses, which could not be explained with these two genes. Our research aimed to resolve the remaining variability of LP horses.”

To do so, Druml and colleagues turned to computerized binarization—essentially, turning spotting patterns into black-and-white data that can be read and analyzed by information systems. They took 90 photos of 90 horses representative of the Austrian Noriker—a classic leopard-spot breed—and fed them into their binarization system. The system was programmed to adjust for differences in each horse’s body shape and position to come to one uniform shape so as to not bias the pattern data analysis. It’s a technique Druml perfected two years ago when analyzing conformation.

By removing factors such as shape and size, the computer programs saw spots—and nothing but spots. The researchers generated an actual numerical order of spotting patterns, placing all 90 horses in a defined position in the lineup.

They then looked at the “removed” factors—base coat color, age, parents’ coat colors, and sex, mostly. And they were able to determine how those factors might have played into the spotting pattern.

They found that base coat color (bay, black, or sorrel) plays a significant role in the resulting spotting patterns, Druml said. For example, bay horses are likely to have less white on the body, whereas black horses are more likely to be full leopards with large, dark, regularly spaced spots. By contrast, a sorrel-based horse might be a full leopard, but his spots will be smaller and more spread out than those of bay or black-based horses.

Sex also appears to play a role, as males tend to have larger spots than females. However, that could be simply because breeders tend to favor large-spotted males, which could artificially influence the genetic effect, Druml said.

While the study was limited to Noriker horses, it’s possible these trends are similar among other leopard-spotted breeds, he said.

Their research could lead to more informed breeding for particular kinds of spots, Druml said. “For breeders who want to produce a horse with big, well-marked spots, evenly distributed over the body, for example, they can maximize their chances by mating a black spotted leopard with a solid black horse, which is homozygous for PATN1,” he said.

But simplified breeding isn’t the only benefit of such a study. Their work can help geneticists in general. “The quality of coat color classification is one of the most important factors for genetic research,” said Druml. “The more precise and more reliable they are, the better they can be used for genetic analyses and research.”

The study, “Phenotypic and Genetic Analysis of the Leopard Complex Spotting in Noriker Horses,” was published in the Journal of Heredity.