Fresh, Cooled, or Frozen?
Written by Kelsey Kempton
Published January 2019
The use of artificial insemination using cooled, and more recently frozen, semen has drastically increased in the past several decades. New technology allowing more consistent cooling rates, better sperm recovery, and worldwide shipping have given us a larger pool of stallions to choose from and more options of how to breed our mares. While there are many factors that determine how a stallion is offered at stud and, as a stallion owner, how you should choose to stand your stallion, this article is going to focus on the pros and cons of using fresh, cooled, and frozen semen, and the variables that a mare owner should consider when choosing the best breeding method for their mare. Fresh semen is still, by far, the most common method of breeding. This can be done either by live covering the mare, either in pasture or in hand, or by collecting the stallion and using artificial insemination immediately after collection. Fresh semen still has the highest motility and best conception rate. This method is also the cheapest, only including a stud fee, and a “chute fee” in most cases. Mares can be covered multiple times over a heat cycle, and fresh semen lasts 48 hours in the mare’s reproductive tract allowing a wider breeding window. The leading downfall of fresh semen is location. You either have to be lucky enough to live close by the stallion of your choice, or travel a long distance to get to the stallion. Travel both before and after breeding can cause a lot of stress on a mare, and even more so if that mare has a young foal at side. Travel can even cause a particularly stressy mare to lose a pregnancy in the early stages. Live cover can also be very dangerous for the stallion, mare, and handlers. One can never predict how even the best trained stallion or mare will react to live cover breeding. There is also an increased risk of STDs or bacterial infections being transmitted during live cover breeding, and there is an increased risk of a mare, or especially a foal, picking up and bringing home a disease whenever they are transported to a new facility. The use of cooled shipped semen is becoming increasingly common. The stallion is collected and the semen is extended and cooled, allowing overnight shipment of the semen across the country, or in some cases, internationally. Cooled semen allows for a wider stallion selection pool and the added bonus of evaluated semen. When semen is collected for shipment it is evaluated for motility and concentration, this ensures the fertility and quality of the semen. Also the risk of disease is lessened with no direct contact between stallion and mare, and bacterial infection is significantly deceased with the use of extenders that include antibiotics. There is less travel and less stress on your mare as well, since your own trusted veterinarian or repro technician can do the insemination. Artificial insemination using cooled or frozen semen is also much safer that live cover. Using cooled semen is more labor intensive than insemination with fresh semen or live cover. The mare’s cycle must be tracked closely so semen can be ordered and delivered before the mare ovulates, and inseminated within 48 hours before ovulation. Cooled semen is only good for 24-48 hours, so timing is incredibly important. There is a lower conception rate using cooled semen and more costs as well. In addition to the stud fee, you also have collection and shipping fees, which recur for every shipment, and additional veterinary/breeding fees for ultrasounds and inseminations. Freezing semen is one of the newest reproductive technologies and, while not as common as fresh or cooled, is gaining popularity. Semen is collected from the stallion, extended, centrifuged to remove the seminal fluid, extended again, and then frozen in 0.5mL tubes and stored in tanks of liquid nitrogen. One of the biggest pros of frozen semen is that it can be stored for an indefinite amount of time, and you can order semen well ahead of time and store it until your mare is ready. Stud fees tend to be cheaper, since frozen semen is usually sold by the dose, and it can be shipped anywhere around the world (as long as international shipping requirements are met by the collection facility). Frozen semen may also be available from stallions that are not currently standing at stud due to competition scheduling, age, injury, or death. Handling frozen semen is a much more complicated process than cooled or fresh. It must be stored at a certain temperature, and thawed at a specific temperature and rate to remain viable. Frozen semen also must be inseminated within 12 hours before ovulation to 6-8 hours after ovulation, so the breeding window is very narrow and mares must be ultrasounded for ovulation in much more frequent intervals. If frozen semen is improperly stored or handled, or inseminated outside the breeding window, conception rates are close to 0%. There is often no live foal guarantee since frozen semen is offered in more limited quantities and shipping fees can be higher, especially with multiple shipments. Fresh, cooled, and frozen semen each have their pros and cons. There really is no right or wrong answer as to which method is the best, but knowing the basics of each method and what to expect when breeding with each can help you to choose the best method for you and your mare.