Page 68 - Speedhorse March 2018

Management factors that can contribute to reduced fertility include using lubrication products that are spermicidal, or spraying the breeding dummy with disinfectant between semen collections for different stallions.
The slides for checking semen need to be at proper temperature and cooled semen should be allowed to warm
up before checking it, otherwise the motility may be reported as low just because the sperm were too cold when viewed.
Cushion products are used when centrifuging semen and enable you to spin the semen longer and harder while recovering more of the sperm without worrying about the pellet being so hard that you can’t re-suspend the sperm.
Semen can be affected if the temperature fluctuates too much in the shipping container. Disposable shippers, which are designed to protect semen and keep it at proper temperature, should not be used repeatedly.
to sperm, so you want to use the minimum amount necessary and use only those lubricants that have the least toxic effects on sperm.”
For instance, if the stallion is allowed
to mount the breeding dummy and doesn’t ejaculate and more lubricant is added and this process is repeated multiple times, the amount of lubricant that can contaminate the ejaculate can be excessive. “This can have an extremely detri- mental effect on semen quality,” says Varner.
Under natural circumstances, semen is transferred directly from the stallion into the protective confines of the mare’s reproductive tract. “When we intercept that semen in an artificial vagina, we need to realize that semen preservation all begins with the collection process. The semen needs to be handled cor- rectly and needs to be in an environment where it is not exposed to light, potential toxicants,
or cold shock,” he says. Semen quality can be
greatly reduced in a stallion that intrinsically has good semen, just by the way we handle it.
“If it’s shipped semen, the way it is shipped can also be a factor in motility,” says Sheerin. “If the temperature fluctuates too much in the shipping container, it can affect the semen. The disposable shippers are designed to protect the semen and keep it at proper temperature, but they are designed to be disposable and not used repeatedly. Some stallion owners reuse them and this is one of my pet peeves.” If a person
is trying to economize by reusing disposable shipping containers, this might be very costly in the end because the semen may not be viable when it arrives.
“Another factor when looking at shipped semen is if poor motility is reported by the people who received it. You may need to know how the semen has been handled at that end and prior to them checking the motility,” he
says. The problem may not be on the stallion end, but on the receiving end, and sometimes a report of poor motility may be due to the way it was checked.
“Some people use the last little drop of semen that is left in the end of the syringe to look at motility. They need to be looking at motility before the insemination. Also, the slides for checking semen need to be at proper temperature and the cooled semen should
be allowed to warm up before checking it,” Sheerin explains. This is where some people go wrong and the motility is reported as low just because the sperm were too cold when checked.
M ed i c a t i o n a n d H o r M o n es M a y Havenegativeeffects
“We don’t know what kind of effect all medications might have on testicular func- tion, but a person needs to realize that any medication given to a horse could potentially have a deleterious effect on semen quality,” says Varner. “Drugs like anti-ulcer medica- tions can have a detrimental effect on testicu- lar function.” Medication may have major
or minor effects, depending on individual stallion response.
Hormones are also known to impact fertility. Some trainers medicate stallions with progestogens (like altrenogest) to reduce aggressive male behavior if that behavior interferes with handling and performance. “Studies we’ve conducted have indicated that in mature horses, such drugs do not seem to have a detrimental effect on semen quality. Studies on young stallions have demon- strated that if the same drug is given in the peripubertal period (when the young horse is reaching puberty), it could have a detrimental effect on semen quality and the possibility exists that the effect could be long-lasting,” he says.
“We’ve examined stallions here that have been treated daily with oral altrenogest as performance horses over a 3- or 4-year period, beginning when they were as young as long year- lings or 2 year olds in training, and they have reduced sperm quality and reduced testicular size. There’s a likelihood that prolonged use of steroids can have a negative effect,” says Varner.
“In some instances, we prescribe supplemen- tal testosterone to enhance libido of breeding stallions. While the effect on libido can be pronounced, testosterone can result in reduced testicular size, sperm output and fertility if given to excess. Blood levels of testosterone must be closely monitored following drug administra- tion, such that the dose can be titrated to mini- mize the likelihood of such side effects.”
Stallion owners and veterinarians can do a lot to improve semen motility, whether they are using cooled semen or live covering mares.
66 SPEEDHORSE, March 2018
equine health