Breeding with Shipped Semen

Equine breeding is a field that has changed dramatically over the last 10-15 years. The use of artificial insemination with shipped semen has allowed local mares to be bred to stallions across the country and around the world. The result is mare owners have a greater number of stallions to choose from and the possibility to produce better foals. The use of shipped semen does have its own set of challenges, requiring a mare owner to have a thorough understanding of the process.

The most common form of shipped semen used in equine breeding is cooled semen. Cooled semen employs a process in which stallion sperm is chilled to enable it to last longer. Similar to the idea of refrigerating food to allow it to last longer. The cooling process allows semen to be viable for approximately 48 hours, giving the semen time to be shipped. The semen arrives either the same day or over night, via Fed-Ex or UPS. The challenge in breeding with cooled semen arises from the fact that the timing of insemination is critical. This is because cooled semen lasts for only about 48 hours, and overnight shipping takes 24 hours. As a result, the most successful time to breed is in the 12-24 hours prior to ovulation. Breeding more than 24 hours before or as little as 1 hour after ovulation, is usually unsuccessful. Because of this mares must be monitored with daily ultrasound exams while in heat. Due to the tendency of the time of ovulation to be erratic, mares are given medications to try to ensure ovulation at the proper time. As a result, careful monitoring and treatment of the mare is critical to achieving success. This requires much greater labor and expertise, which increases cost. Also, while cooling semen results in longer shelf life it also reduces the chance of conception. On average, breeding on one cycle has only about a 50% chance of achieving a pregnancy. These odds can be improved by having your veterinarian closely monitor the mare through her cycle. By planning to breed for more than one cycle, the odds are also improved. Close to an 85% chance of conception can be obtained by breeding a mare for three cycles.

So how does a veterinarian know when the right time to order semen is? The advent of ultrasound machines has enabled veterinarians to examine the reproductive tract in much greater detail than before. By using the ultrasound, the precise size of a follicle or egg can be determined. Follicles generally reach a size of about 40-50 mm before ovulation. By knowing exactly what size the follicle is and how much it is growing each day, your veterinarian can predict the time of ovulation.   In addition, changes that can only be monitored by ultrasound occur in the uterus prior to ovulation. A further advantage is the ability to recognize problems such as the accumulation of uterine fluid or anovulatory follicles, which cannot be determined without ultrasound examination. If these problems are not recognized and corrected they will prevent pregnancy.

Breeding with cooled semen is a challenging undertaking. By having a better understanding of the process, you can decide if it is going to be a worthwhile investment of your energy and money. An investment that can yield the return of an exciting return of a new foal.