“Roaring” is the name given to the condition of Equine Recurrent Laryngeal Neuropathy (RLN), an often bilateral (both sides affected) condition that affects the horse’s laryngeal area. The weakness and paralysis of the affected structures can lead to the blocking of the airway and the creation of the distinct noise for which this condition has been named. A higher prevalence of this condition in the offspring of RLN-affected sires vs. unaffected sires led to the suggestion that there might be a genetic component to this condition.
Research in Thoroughbreds investigated this very idea. 505 thoroughbreds of recorded height were examined by endoscope while unsedated, and a laryngeal grade was given to each horse based on its laryngeal function. Horses were then divided into a control group (grade 1-normal laryngeal function) and an affected group (grades 3 and 4, impaired function). Once the data was analyzed and gene mapping was done, they found a significant association of RLN with a specific loci on DNA that was previously shown to affect body size in horses. This study supported the anecdotal observations that taller horses were more likely to be roarers. The data from this study suggest that 16 and a half hands are the threshold – horses of that height and taller are more likely to be roarers.
Many different breeds, including Friesians, have been diagnosed with this condition. It stands to reason, then, that this is definitely good “food for thought” as this breed continues to evolve to meet market demand.
Scientific article: Boyka, AR, etc al. “Genomic analysis establishes correlation between growth and laryngeal neuropathy in Thoroughbreds”. BMC Genomic, April 2014, full text available on line.
Companion Article: Barakat, C, McCluskey, M., “Genetic ties to “roaring’ identified”, EQ Medical Front, Equus July 2014, issue 442, pp.8-9.