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By Daniel H. Grove, DVM

Well, it is March and breeding season is here. I thought it might be a great time to talk about equine reproduction and some of the options available to horse owners in our area. Things to consider in preparation of getting your mare in foal are the mare preparation, how you will receive your semen, and who is going to be inseminating the mare.

Mare preparation is important for a successful pregnancy. The goal for the horse owner is usually to get the mare in foal as soon as possible for an early foaling. Also, the more times you need to breed the mare, the more your costs go up. Whether you are shipping in semen or taking your mare to the stallion, it all adds up. First, starting in late November or early December, you should have started having your mare under lights. Between the natural sunlight and the artificial light you provide, it should be somewhere around fifteen to sixteen hours per day. The mare should not be able to have her head in any spot in that time that is dark. The next step in getting her ready would be to have a culture and/or biopsy of her uterus. Whether one or both of these are necessary is up to your veterinarian. I choose whether or not to do them based off of the history of the mare. Mares that are prone to problems are more likely to get the works! Lastly, any vaccines you want your mare to have, get them done before trying to breed her. The inflammatory response to the vaccine can be detrimental to an early pregnancy. It is very frustrating to get a mare in foal in February just to lose the pregnancy in April and have to start over.

Just like us humans, to get your new foal, it takes two to tango. Selecting the stallion to best suit your mare is going to be your first priority, but you need to know some of the advantages and disadvantages of the different ways to get his genetic material into your mare. First is the tried and true natural way of live cover. The stallion breeds your mare directly and leaves his DNA in the process. You get the whole ejaculate so sometimes you get higher fertility rates. Also, it is lest costly than assisted reproduction. Some of the disadvantages are that the mare or the stallion are more likely to get injured. A mare can kick and hurt the stallion or some stallions are very aggressive and can injure your mare. Also, both the mare and the stallion are at increased risk of contracting STD’s(Sexually transmitted diseases).

The second,and probably the most common, is cooled shipped semen. The stallion is collected at his farm and either your mare is there and inseminated or the semen is shipped to you via overnight courier or an airline. Your veterinarian will be checking your mare to determine when she will be close to ovulating and will order the semen accordingly. This process is more expensive with veterinary fees and shipping costs. Fertility rates are often very high. The stallion has zero risk of disease from your mare. Your mare can still get some of the STD’s out there from him. There is no risk of injury to your mare from the stallion, but anytime you ask a veterinarian to check your mare, there is a small risk of injury to the mare. If the stallion cools and ships well, this is an excellent way to go. Some stallions’ semen will survive for several days this way. Some don’t do well at all. Always inquire about the quality of the shipped semen when choosing to go this way.

The last way to receive semen is if it is frozen. There is no overnight shipping charges, but often times the extra veterinary costs surpass that. Ideally, the mare is inseminated just before and just after ovulation. It requires more frequent checking of the mare. Just as with cooled semen, some stallions freeze well and some do not. An additional benefit is that you can get semen from overseas since it does not have to be overnighted. Fertility rates tend to be lower than with live cover or cooled. Also, some of the stallion contracts do not offer a live foal guarantee. Instead, they sell you a given number of doses of semen and you get that many chances to breed your mare.

We have talked a lot about the stallions donation, but what about the mare’s? The semen has to get to the oviduct to fertilize the egg. It needs to travel through the uterus to get there. If the uterus is not a hospitable environment for the sperm cells, they can be killed before ever making it there. If the sperm do make it and fertilize the egg, then the uterus needs to be ready to receive the fertilized ovum and nurture it as it grows into an embryo and then, a fetus. If due to numerous possible factors this entire process cannot take place, fear not, you do have options. The first is embryo transfer. After approximately 7 days post ovulation, the mare is flushed and the resulting fluid is collected and searched for an embryo. That embryo can then be either implanted into a recipient mare, or frozen to be implanted later. If you have a mare that has uterus problems,this allows for a healthier uterus to carry the foal. If you want multiple foals from the same mare in the same year, this makes that possible.

An additional option for those mares that may have problems is ICSI. This stands for intracytoplasmic sperm injection. Here is where you can get your “test tube” foals. The eggs are harvested directly from the ovary and are manually fertilized by a reproductive specialist. This is an expensive procedure with increased risk to the mare during oocyte collection. If you have a great mare with a damaged uterus or oviduct that cannot get you a seven day old embryo to flush out, this is your last stop. Also, if you have a stallion that is either deceased or has very limited semen, this may be an additional tool to help. A single straw of frozen semen, which is usually just a partial breeding dose, can be used over and over to fertilized many eggs.

This is just a brief overview of the different possibilities in equine reproduction. As you can see, there are different avenues you can travel down in the process. It may not always be successful, or as inexpensive as you may want, but the result is a new life that you get to raise and mold into hopefully the horse of your dreams!


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