Horse-Breeding Soundness, Part 1

A regular evaluation on your stallion is a wise investment.

From The American Quarter Horse Journal

A breeding soundness evaluation should be a part of any stallion's regular health check-up to head off unseen problems prior to breeding season. Journal photo

A formal breeding soundness evaluation on a stallion sounds about as interesting as a 10th-grade term paper. But going through a BSE on a horse with a fertility problem can unfold like a scientific who-done-it, and it can save big management dollars for a farm.

People typically think of conducting a BSE for three reasons: as part of a pre-purchase exam; when a stellar performer first enters the breeding shed; and when there’s a sudden fertility problem in a previously sound breeder.

However, experts say that a BSE should be a part of any stallion’s regular health check-up to head off unseen problems prior to breeding season, and it can be an important management tool for his breeding career, for example, as the demand for his services increases or as he ages and his physical capabilities change.

But the stamp of “pass” or “fail” on a horse as a successful breeding stallion often depends on variables outside of what the technical analysis reveals.

“The final evaluation itself changes, depending on how you are going to use the horse,” says Dr. Jason Bruemmer, professor in the department of animal sciences at Colorado State University. Stallion behavior, physiology and management are his primary research fields, and he directs the stallion services offered at CSU Equine Reproduction Laboratory.

“For example, is the stallion physically able to work into your program?” he continues. “And the answer could be different if you’re using artificial insemination or live cover or frozen semen. You could have different answers for the same horse.”

There are standards regarding what a basic stallion BSE should entail. These standards are established by the American College of Theriogenology as recognized by the American Veterinary Medical Association. Any veterinary school, reputable reproductive facility or veterinarian should follow those. Here’s how a typical BSE goes at the CSU Equine Reproductive Laboratory.

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Case History

Prior to the BSE, the lab notes the stallion’s general history, why he’s being evaluated and any breeding history or previous evaluations. Everything about the stallion’s lifestyle and use has a potential affect on his reproductive performance.

“Is he exercising or standing in a stall? Currently breeding or breeding and being shown? Is he a performance horse, a halter horse or a racehorse?” Dr. Bruemmer lists off as examples.

“Often, owners don’t want to talk about the effects of a stallion’s lineage on his reproductive performance, but we have to,” he says. “I know of one line of horses that has a high incidence of double-headed sperm cells (an indication of infertility), but they are all very fertile. It’s amazing to see that.”

Medications, injury or recent sickness can also affect a BSE: “Spermatogenesis in the stallion is 57 days,” Dr. Bruemmer says. “If a stallion has been injured, sick or on medication in the 60 days prior to the BSE, that will affect the semen we collect.”

Physical Exam

The BSE itself begins with a basic physical exam: checking for lameness, pulse, respiration and body condition - being overweight makes it physically harder on a horse  to mount a mare or phantom. As the stallion is washed prior to collection, his penis and sheath are evaluated and examined for scarring or lesions.

“I don’t do a testicular palpation until after we’re done collecting because that’s when the stallion is the calmest,” Dr. Bruemmer says.

At that point, he checks for cryptorchisism (one testicle instead of two) and the testes’ consistency. He uses calipers to measure the total scrotal width, height and length - to calculate total scrotal volume.

“The total scrotal volume is predictive of what the stallion should be able to produce on a given day,” he explains. It can also help flag potential problems, comparing predicted sperm production with the actual numbers."

The lab will also take bacterial culture swabs pre- and post-ejaculation.

“There are always going to be bacteria present,” Dr. Bruemmer says. “We just want to make sure there aren’t any pathogens.”

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Regarding the stallion’s libido, Dr. Bruemmer doesn’t track the total time of erection, mounting and ejaculation, because those behaviors are affected by handling.

“That’s why it’s nice when you can have them for a week and handle them regularly,” he adds. “For example, you might use a gray tease mare and not realize he has been kicked by a gray mare and that’s what’s taking him so long.”

It has also been Dr. Bruemmer’s experience that behavioral problems typically stem from either a stallion being young and inexperienced, or in how the stallion has been trained either to breed or in his performance career.

“The one problem we run into more than anything else is not necessarily that they are infertile or subfertile,” Dr. Bruemmer says. “It’s behavioral issues.”

That’s another good reason to start a young stallion off with a BSE - to learn proper breeding shed etiquette and behavior.

“If he goes through a BSE at the beginning of his breeding career, it’s like sending him to college,” Dr. Bruemmer says. “Get a BSE, a test cool or freeze, and let him learn how to mount a phantom properly and be collected. You get all the data you need, and he gets a good start, behaviorally.”