Those of us who work with stallions are routinely asked to determine a stallion’s fertility prior to breeding mares or to investigate the cause of low fertility. Often this requires sending the stallion to a specialized veterinary clinic or a veterinary school. Advances have been made in stallion fertility evaluations through the use of computerized sperm motion analyzers (CASA) and flow cytometry.
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Fertility of Equine Frozen-Thawed Semen Stored Cooled After Thawing
There are numerous advantages of frozen semen. If maintained properly in liquid nitrogen, frozen semen will last indefinitely. This allows frozen semen to be shipped to the mare and the mare bred at the most opportune time, close to the time of ovulation. One other use of frozen semen that seems to be gaining in favor is for farms to ship frozen semen to mares when there is a shortage of cooled semen. Alternatively, the breeding farm uses frozen semen to breed mares housed at the farm and ships out the cooled semen. Thus, frozen semen becomes the "backup plan" for breeding mares. You can find additional information to consider when deciding if frozen semen is a fit in your breeding program by reading these articles on the SBS Website: ‘Why Freeze Stallion Semen?’, ‘The Pros and Cons of Equine Frozen Semen’ and ‘The Hidden Value of Frozen Semen’.
High Prevalence of Latent Endometritis in Problem Mares: Effect of Activation and Treatment on Fertility
Beta-hemolytic Streptococcus equi subsp. zooepidemicus (BHS) is the most frequently isolated pathogen in the uterus of mares. However, in a large fraction (>50%) of subfertile mares there is no obvious reason identified. We recently demonstrated that BHS have the ability to reside deep in endometrium and may also gain intracellular access. The ability to escape and hide from the immune system allows BHS to cause long lasting, hardly detectable infections. In addition to this, we have shown that BHS are able to enter a dormant state where the bacteria can slow down their metabolism. Most antibiotics inhibit bacterial growth by disrupting the microbial metabolism which makes the dormant bacteria highly tolerant to antibiotics.
Unexplained Subfertility in Broodmares
Breeding season is just around the corner and most breeders dread the frustration of subfertility in certain broodmares. A thorough breeding history is key to diagnosing the cause of subfertility. Questions that address previous breeding management, stallion selection, and general wellness are important when performing a breeding soundness evaluation. Diagnostics such as trans-rectal palpation and ultrasound examination of the reproductive tract, vaginal speculum examination, digital cervical palpation, endometrial cytology and culture, endometrial biopsy, and hysteroscopic examination are useful in determining the cause of subfertility. Typically, a cause of subfertility can be determined utilizing the diagnostics mentioned above, but there may be some cases in which diagnostic test results are negative and yet a mare is still subfertile. So what’s next?
Progesterone Therapy for Pregnant Mares-Part 2: Common Questions
Thank you to Dr. Pat McCue from the Equine Reproduction Laboratory for last month’s article, Progesterone Therapy for Pregnant Mares – Part 1, in which he reviewed the formulations and use of progesterone therapy in mares. Dr. McCue did a yeoman’s task in outlining the formulations and principles of therapy available to veterinarians for the suppression of estrus, pregnancy support, and treating cases of suspected or diagnosed placentitis. However, the maintenance of pregnancy is by far the most common area in which we receive questions about supplementing mares with exogenous (therapeutic) forms of progesterone.
Progesterone Therapy for Broodmares: Part 1
In preparation for our annual SBS Affiliate meeting, I was speaking to Dr. Patrick McCue (my friend and mentor and honored guest speaker this year’s meeting) about the commonality of questions I have from clients. By far, the most discussed topic is supplementation of progesterone to pregnant mares to help them maintain a pregnancy. Many times, the questions stem from the necessity of such therapy, duration, and efficacy of supplementation. Sometimes, even with the best therapy, we fail to reach a good outcome, but the following discussion about the forms of supplementing progesterone is well worth a quick read for any breeder.
The Equine Gut Microbiome
The gut microbiome has become a popular topic of interest in recent years as scientists are beginning to understand the vast impact it can have on overall health and development in both humans and animals. A microbiome is defined as the collection of genomes of the microorganisms that reside in a specific environment . In regards to the gut microbiome, it is comprised of the genetic material of the microbes that inhabit an organism’s gastrointestinal system. In the horse, this microbiome includes bacteria, yeast, fungi and protozoa where the most functionally important microorganism is thought to be bacteria. Researchers have studied how this microbial community can affect not only the digestive tract, but also the immune response, endocrine system, behavior and even cognitive function.
Endocrine Diagnosis of Infertility in the Stallion
Diagnosis of infertility in stallions usually starts with a complete reproductive history and then collection of semen to evaluate seminal parameters, testis size and the potential presence of bacteria in the semen. A more detailed evaluation might also include drawing blood for hormonal analysis.
Measuring Hormone Levels in Mares
Endocrine diagnostics certainly have a place in the routine management of mares and stallions as well as in diagnosis of problems and diseases. However, there are likely more applications for measuring hormones in mares than stallions. Dr. Ed Squires will discuss the hormones tested in mares in this article and will then cover the testing of stallion hormones in a subsequent article.
Methods to Obtain the Concentration of Sperm in a Stallion Ejaculate
Knowing and keeping track of the concentration, or the number of sperm per milliliter, of each ejaculate for a stallion is very important for a variety of reasons. The concentration of his semen, along with the volume of his ejaculate, is used to determine the total number of sperm he produces in a given collection. These two numbers (volume and concentration) are used to calculate insemination doses. Also, keeping a record of each number can help stallion managers recognize if there are any changes in the reproductive health of the stallion. Slight variations are likely nothing to be concerned about. However, if the number of sperm in the ejaculate varies drastically, from collection to collection or a steady decrease in his total number of sperm over time, one may begin to ask what is causing the change. This information is valuable so that any concerns can be addressed as soon as they arise.