Semen Comparison: Live Cover, Fresh, Fresh Cooled, Frozen

Written By: Pat Griffin, DVM, PhD, DACT

Written By: Pat Griffin, DVM, PhD, DACT

After you’ve spent months considering what a good stallion match is for your broodmare, what your foal will be used for, the cost, pros, cons, and availability of your various stallions, you’ve finally picked the stallion to breed to your mare. The subsequent parts of the process will have as much of an effect on your expenses and the success of the breeding as the stallion choice. Here, we’ll walk you through the various options for breeding, including live cover and artificial insemination. Regarding artificial insemination, we’ll cover fresh, fresh cooled, and frozen semen.

Which method is best?

The first misconception to get out of the way is that one method is, by definition, better than the rest. When it comes to breeding your mare, there are a number of factors that play into a successful outcome. While we won’t give you one answer for what’s “best”, we’re going to give you a lot of information so that you’re able to make an informed decision.

Which method should I choose for my mare?

This is extremely stallion and mare dependent. The success of a specific breeding and breeding method depends a great deal on the mare, her age, her prior number of pregnancies and the health of her reproductive tract.

In general, there is a perception that live cover has a better pregnancy rate per cycle than artificial insemination. Again, this isn’t always true – it depends on how the stallion is being managed, his age and soundness, the number of mares he’s booked to, the type of mare he’s breeding, and more. However, old dogma will tell you that live cover has the highest pregnancy rates, followed by artificial insemination with fresh semen, fresh-cooled semen and, finally, frozen semen. There are many stallions that are very fertile with fresh or fresh-cooled semen, and lose significant fertility with frozen semen. Similarly, a stallion's fresh-cooled semen may not ship very well at all, but can withstand the freezing process quite well. Unfortunately, quite a bit of the sub-fertility on these stallions is man-made. Who is handling the stallion and processing the semen?  Are they doing everything correctly? Are all of the pieces of equipment clean, dry, and at the right temperature? Have you exposed the semen to light or temperature that would harm it? Are you inseminating the mare at the right time, and are you making sure she’s ovulating? Is she being examined on the days following breeding?  There are many steps to a successful artificial insemination, which requires both expertise and experience.

What factors should I consider?

Historical pregnancy rates – If the stallion manager will release the information, you should ask for historical numbers on the stallion’s per-cycle pregnancy rates (not his seasonal rate) for the various forms of AI in which he is being offered. This includes fresh semen, frozen semen, and fresh-cooled semen. In general, a per-cycle pregnancy rate of >60% per cycle is the industry-accepted level of fertility for a stallion for live-cover, fresh or fresh-cooled semen. For frozen semen, the knowledge that the individual stallion’s frozen semen has resulted in pregnancies is the crucial piece of information needed prior to investing in doses of his semen.

Mare management – Consider your veterinarian’s ability to manage your mare. If you’re far from your mare and aren’t confident in her management, that should play a significant part in your decision about semen form selection. With fresh or fresh-cooled semen, the semen can live in the mare’s reproductive tract for an extended period (days, not hours), depending on the individual stallion. If you can’t predict time of ovulation precisely, you still have an opportunity to achieve a pregnancy. With frozen semen, there is a much shorter “life” expectancy of the sperm cells in the mare’s reproductive tract. Ideally, we have an approximately twelve-hour time frame surrounding ovulation to inseminate the mare for optimal success – 6 hours prior to and 6 hour after ovulation. If you miss that window, your chances of a pregnancy are much lower.

Mare age and Reproductive Status– While we will, and do, breed older or problem mares with frozen semen, it’s not the ideal scenario. In these cases, close mare management (pre- and especially post-breeding) is crucial for success and your expectations as a mare owner should be tempered by the knowledge that we may need to breed the mare over multiple cycles. If the option is available, we do recommend these mares go to fresh or fresh-cooled semen to optimize our chances of a pregnancy, while minimizing frustration and costs.

Progressive Motility – This is the buzzword or phrase that many breeders want to hear about and hang their hat on. However, it is only one factor out of five or six that we consider to assess potential fertility. Progressive motility does give us an idea of the viability, not fertility, of the sperm cell. When considering fresh (non-processed semen), progressive motility, and its maintenance, is roughly correlated with levels of fertility. However, during the processing of semen, whether cooling or freezing, that positive relationship between progressive motility and fertility becomes less defined. There is even some thought that non-motile cells (fresh-cooled or frozen) regain their motility after entering the mare’s reproductive tract.  Make sure your veterinarian is considering the other aspects of semen evaluation as well.

What questions do you have?

There are a lot of unanswered questions here, and that’s because each situation is unique! Contact us today to talk about breeding your mare or standing your stallion at stud.