QUESTION: Are roaring or other common throat issues hereditary?
DR. BART BARBER: It is an interesting question, and I believe the answer is yes, though I believe at the current time we cannot answer this question definitively. There are no studies, of which I am aware, that address this issue. Therefore, the following is based on my own experience and opinion.
There is a wide variation of how a horse's throat looks and functions. It is safely assumed that there is a familial influence on the conformation of a horse's knees, the slope of her pasterns and the length of her ears. It makes sense to assume that genetics have an influence on the shape, size and function of the throat.
Both sides of the genetic equation should be considered in this question. It is possible to examine the throats of over 100 of the offspring of a particular sire in a single crop, compared with a mare who can only have one a year. I can think of several sires whose progeny, most veterinarians would agree, are not blessed with the most straightforward throats. The findings of the standing endoscopy on these offspring are commonly found to be less than ideal at what seems to be a higher rate than the norm. This does not necessarily mean that they don't run or that they won't sell well. To the contrary, some of these stallions are our most successful sires.
Likewise, among mares, there are several that I can think of who have had two or more of their offspring that have had suboptimal endoscopy findings. In my experience, it has not been consistent, meaning not all of the foals out of a single mare have deficiencies.
Remember, if detrimental throat abnormalities have a strong familial influence, then we are already selecting against them. Horses with these deficiencies generally don't race well and, at least for the males, don't pass on their genes. There are exceptions. Some very successful racehorses have had tiebacks during their racing careers, then go on to have a career in the breeding shed.
There is a lot of work that could be done with this to determine how heritable these conditions are. Until then we should all proceed with caution in making too much of the coincidences and barn chatter. It is very likely these conditions are multifactorial and we will never be able to pin the cause onto a single factor.
Good horsemanship and common sense should still be the rule.
Dr. Bart Barber, DVM, is a shareholder in Rood and Riddle's veterinary practice and specializes in reproduction, primary and preventative ambulatory care, as well as operations at Rood and Riddle Veterinary Pharmacy.
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