The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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39 December 2017 THE HORSE TheHorse.com weather, etc.—can be detrimental to se- men production and quality, says Sheerin. "It often depends on the duration of the stress, so we need a good historical perspective when a stallion comes in for an examination and has reduced semen quality," says Varner. 12 Age In some breeds and disciplines, stallions might not enter the breeding pool until their performance careers are over—careers that might last until they are 20 or older. "Then their fertility problems may be due to age-related testicular dysfunction," says Varner. All males, including stallions, develop age-related testicular degenera- tion eventually. "This condition can affect some stal- lions in their early teens, whereas it may not become apparent until early to late 20s in other stallions," he says. "The condition is associated with reductions in testicular size, sperm output, and semen quality, and results in reduced fertility or even sterility in advanced cases." "Typically, the older horse will have smaller testicles—and probably softer testicles—and high-volume ejaculates with low concentration of sperm," says Squires. "That combination equates to a lower quality of semen." Breeders will notice conception rates dropping. 13 Housing & Social Environment Whether stallions interact with mares or only other male horses also impacts semen quality. "Stallions that are housed together, such as in the same barn, have hormonal profiles very similar to bachelor stallions that have no interaction with mares," says Sheerin. "Their sperm numbers are lower, testosterone levels are lower, etc. Stallions that can see or interact somewhat with mares will be more like a harem stallion and will have higher testosterone levels, better libido, and better semen quality." 14 Improper Collection If the stallion is being collected for breeding via artificial insemination, a number of human mistakes can affect semen viability. These include: Too much lubricant "All lubricants are potentially detrimental to sperm, so you want to use the minimum amount neces- sary, and use only those lubricants that have the least toxic effects on sperm," says Squires. For instance, if the stallion mounts the breeding dummy and doesn't ejaculate, and more lubricant is added to the arti- ficial vagina (AV) before he mounts and does not ejaculate again, and the cycle continues, the amount of lubricant con- taminating the ejaculate can be excessive. "Some people use the whole tube of lubricant on their sleeve to lubricate the AV, but it only takes a small amount," says Squires. "There are also some good nonspermicidal lubricants on the market today that can help with this problem." Temperature "If the AV is too warm—or too cold—when you collect a stallion, this may damage the sperm," says Squires. "If you don't drain the water (which deter- mines the AV temperature) out of the AV quickly enough, this can also damage the sperm" as it warms. Contamination "You need to wash the penis to make sure you get a good, clean collection," says Squires. "Otherwise, this may have an impact on motility and sperm quality." Improper cleaning If the AV or dummy has been cleaned with something that has spermicidal qualities, the semen may be ruined. "Some people spray the breeding dummy with disinfectant between semen collections," says Varner. "Chlorhexidine can have an adverse effect on sperm if the stallion's penis comes in contact with this disinfectant on the breeding dummy." Dilution with presperm fluid Make sure you collect the proper portion of the ejaculate. "There are three components in the ejaculate," says Squires. "One is pre- sperm, one is sperm-rich, and one is a gel. The presperm 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 on out. Then we put the AV on the horse and get the sperm-rich fraction." Also remember that the horse usu- ally doesn't ejaculate on the first mount. "He often takes multiple mounts," says Squires. "If you don't change the col- lection bottle each time, you get a lot of presperm in the bottle." Under natural circumstances the stal- lion transfers his semen directly into the protective confines of the mare's repro- ductive tract. "When we intercept that semen in an AV, we need to realize that semen preservation (whether it's to be fro- zen, cooled, or used within the hour) all begins with the collection process," says Varner. "The semen needs to be handled correctly and needs to be in an environ- ment where it is not exposed to light, potential toxicants, or cold shock." Take-Home Message Many factors can affect semen quality. If a stallion has a fertility problem, work with your veterinarian to determine and address the root issue. "Often the stallion owner wants to find a simple answer like a supplement or an injection, but there is no silver bullet to change poor semen quality into great se- men quality," says Sheerin. What you can address are body condi- tion, collection methods, housing and social environment, and stress levels. Other factors, such as genetic and breed differences, might be irreversible, and you must work with those limitations. h Stallions allowed to see and interact with mares will have higher testosterone levels, better libido, and better semen quality that those housed with other stallions. PAULA DA SILVA