Page 67 - Speedhorse March 2018

Dr. Peter Sheerin, owner of Nandi Veterinary Associates in New Freedom, Pennsylvania.
without worrying about the pellet being so hard that you can’t re-suspend the sperm. This is some- thing to consider for
a horse that does need his semen centrifuged so you can increase the yield while not losing as much sperm,” he explains.
Not all stallions
are blessed with high fertility and high sperm counts, so it may take some extra effort to
There are always a few unusual cases and instances in which motility and fertility is impaired. “I suppose there are some potential toxins that a horse might consume that would impact reproduction, but most stallions are on a good diet and aren’t out in a pasture eating toxic weeds. Unless there is a toxin that acci- dentally gets into the feed at the commercial feed mill, the chances for a valuable stallion consuming toxins is low.”
The important thing is to keep the horse on a good plane of nutrition with a balanced diet and adequate exercise. If he is healthy, fit and in good body condition, his potential fertility and semen motility should not be impaired unless the semen is handled inappropriately during collection, preparation and handling.
HumAn mismAnAgement CAn HAve A d v er s e ef f eC t s O n s em en
When a horse has a problem with motility, you should consider the collection, handling and preparation of the semen. If you are using lube in the artificial vagina (AV) when collect- ing the stallion, be aware that some lubrication products are potentially spermicidal and could impact semen motility. “If water gets into the AV or if the AV is too hot or too cold, this can also impact motility. If the AV is too hot or has been cleaned with something that may kill the sperm, the semen may be ruined,” says Sheerin.
Another factor in semen motility problems could be improper preparation of the stallion. You need to wash the penis to make sure you get a good, clean collection. Otherwise, this may have an impact on motility and sperm quality, according to Edward Squires, PhD (Adjunct Professor, Department of Veterinary Sciences, at the University of Kentucky).
Making sure you are getting the proper portion of ejaculate that is not diluted by pre-sperm fluid is important. “There are three components in the ejaculate. They are pre-sperm, sperm-rich and gel. The pre-sperm comes first and sometimes there may be quite a bit of it. We typically like to hold the penis away from the AV for a moment and let that pre-sperm go out. Then we put the AV on the horse and get the sperm-rich fraction. That’s always a good technique to deflect the penis and let the pre-sperm come out first,” Squires explains.
Another thing to keep in mind is that the horse usually doesn’t ejaculate on the first mount. “He often takes multiple mounts. If you don’t change the bottle each time, you get a lot of pre-sperm in the collection bottle from the multiple mounts and this can be detrimen- tal to semen quality,” says Squires. These are some of the negative things that can happen when people aren’t paying enough attention to the collection process.
Anything that interferes with optimum temperature for sperm production can impact fertility.
maximize their ability to settle mares. When breeding horses, we select for athletic ability, speed, etc. Fertility is often low on the list of desired traits, so there are many stallions that don’t have optimum fertility. You may have an exceptional racehorse and want to use him as a sire to produce offspring, but his sperm just isn’t the best.
There are several things that might have a temporary impact on motility, including heat shock or cold shock to the stallion’s testicles. For optimum fertility, the semen must be kept a few degrees lower than body temperature. Therefore, the stallion raises and lowers his testicles to drop them down from the body in hot weather and raise them up against the body for warmth in cold weather. Anything that interferes with optimum temperature for sperm production can impact fertility.
“If the horse has been ill and has had a fever for a period, the elevated temperature can impact motility and fertility. Extremely hot weather may also be a problem. Likewise, if he gets frostbitten testicles. This can make him temporarily infertile and impact motility. Stallions are less likely to suffer frostbite than bulls, however, since bulls have a more pen- dulous scrotum and lower-hanging testicles.” The worst situation would be severe cold in conjunction with wind chill.
Most stallions, however, would not be win- tering outside with no windbreak. “If he’s your valuable stallion, you wouldn’t have him out there in a blizzard. He’d be housed in the barn, out of the wind. With most stallions, the more likely problem would be heat shock rather than cold shock,” says Sheerin.
“We sometimes see fertility and motility prob- lems in overweight stallions because there is too much fat in the scrotum,” he says. The layer of
fat around the scrotum insulates the testicles too much, which hinders the horse’s ability to regu- late the temperature and the sperm may become too hot. These stallions can be helped by having more exercise and fewer calories to trim down the fat. They need to be in good body condition.
Seminal plasma is toxic to sperm and can interfere with motility and the length of sperm life. To reduce this problem, the semen is centrifuged and the seminal plasma is discarded.
Dickson Varner, DVM, MS, Diplomate ACT, Professor and Pin Oak Stud Chair of Stallion Reproductive Studies at the College of Veterinary Medicine and Biomedical Sciences, Texas A&M, explains that sometimes when people are collecting stallions, the semen qual- ity may be adversely affected by mismanage- ment even though the stallion has good semen to start with. “I recently consulted with a large breeding operation that had some issues with reduced semen quality. Some of the manage- ment factors that likely contributed to reduced fertility include spraying the breeding dummy with disinfectant between semen collections for different stallions. Chlorhexidine can have an adverse effect on sperm if the stallion’s penis encounters this
disinfectant on the
breeding dummy,”
he says.
“Some artificial vaginas are cleaned with a disinfectant like chlorhexidine, and this can be extremely detrimental to sperm. Lubricants used for artificial vaginas can also be a problem, especially
if used in excess. All lubricants are poten- tially detrimental
Dickson Varner, DVM, MS, Diplomate ACT, Professor and Pin Oak Stud Chair of Stallion Reproductive Studies
at the College of Veterinary Medicine and Biomedical Sciences, Texas A&M.
SPEEDHORSE, March 2018 65
equine health