Breeding Your Mare

by Danielle Spade, DVM

You have decided to breed your mare… So all you do is put your lovely mare and the chosen stallion in a dark room, light some candles and put on Let’s Get It On by Marvin Gaye, right?  Unfortunately, it is not so easy.  Before you start out on the big adventure of breeding your mare, here are some factors to consider. 

1) Physical Examination

A mare needs to be in good physical condition and have a good plane of nutrition in order to cycle regularly during the breeding season, become pregnant and successfully carry a foal to term. A de-worming, dental and vaccination program also needs to be in place and can be discussed during the physical exam.

2) Reproductive Soundness Examination

A breeding soundness exam will involve an external as well as an internal examination of the mare’s reproductive system. Externally, poor vulvar conformation can cause a number of reproductive problems such as wind sucking, urine pooling, or may make a mare candidate for uterine infections. Internally, ultrasound can be used to detect fluid, cysts, or tumors anywhere along the reproductive tract, which could cause infertility. Rectal palpation can determine structural abnormalities within the cervix, uterus, uterine horns, or ovaries. A speculum examination can help evaluate the cervix, whose job is to help maintain pregnancy.  A uterine culture can evaluate the uterine environment for bacterial infections.

Additionally the age and health of your mare will be taken into consideration when determining her reproductive soundness.  Older maiden mares can be more difficult to get into foal than young maiden mares, but this depends on the condition and health of your mare.  If your mare has been bred before, knowing her reproductive history can help ease the breeding process.  How successful your mare was in her last pregnancy, the ease that she got in foal last time, as well as any post foaling complications affect her reproductive soundness.

3) The Stallion

The most exciting part (besides the foal, of course)!  Picking out a stallion is very important.  There are some imperative questions that must be answered before one signs the contract and pays the fees.  Take time to consider what type of horse you are breeding for.  Not all horses will go to the Olympics, win the Kentucky Derby or capture the Snaffle Bit Futurity.  Consider what qualities such conformation, temperament or athleticism, you can improve in your mare and chose a stallion that will compliment her.  If you want to register your foal under a certain breed registry make sure that both stallion and mare qualify. 

The next question is whether the stallion is offered with cooled, fresh semen, frozen semen or live cover.  If your stallion is offered with fresh semen, make sure that he will be available when your mare is ready and ovulating.  Make sure that the stallion is fertile and disease free (EVA negative).  Ask questions about conception rates, percent motility, morphology, how well semen freezes (if breeding frozen) or how well semen ships (if breeding fresh).  If you are unsure, ask your veterinarian or breeding manager at the facility where you plan to breed your mare about what further questions to ask.

Read your stallion contract!  Is there a Live Foal Guarantee (LFG)?  Find out what happens if the stallion or mare dies before you get a foal.  Make sure you know what responsibilities you have in order to fulfill your end of the contract and communicate them to your veterinarian or breeding manager.  Insure that there is a clear and open communication between you, (the owner or leaser) and the stallion owner. 

Bottom line: Research your stallion. 

3) Timing

Horses are long day breeders. The hormones that control their heat cycles are controlled by the amount of light the mare is exposed to, which means that horses naturally cycle in the spring.  This leads us to next important question.  When do want your foal to be born?    One can manipulate the ovulation cycle by artificially increasing the amount of light present.  A mare needs about 60-90 days of artificial light before she starts to cycle. A 150 to 200 watt light bulb in the middle of a 13’ by 13’ stall is sufficient.  Turning on the lights before sunset and keeping them on until 11pm will increase the amount of light to 16 hours that will simulate the length of light perceived in the spring.

4) Hormone therapy.

Hormone therapy can help increase fertility, stimulate estrus and help maintain pregnancy.  Hormone therapy is also sometimes used in conjunction with light therapy when trying to stimulate estrus. This can be time consuming, as mares need multiple injections daily, over the course of weeks. Progesterone is commonly used for pregnancy maintenance and is accepted as safe in the pregnant and lactating mare. Produced by the ovaries and then the placenta, progesterone prepares the uterus and lining to accept the fertilized egg and nurture the embryo. The level of progesterone in the mare’s blood can be measured to see if she needs additional progesterone to help maintain her pregnancy.

5) Planning Ahead

By planning ahead starting with a breeding soundness exam, you can avoid some of the potential frustrations involved in breeding your mare.  It would be unfortunate to spend a lot of time and money to only discover that your mare is not capable of becoming pregnant or maintaining a pregnancy.  If you have any questions concerning breeding, our well-trained staff here at The Equine Center can answer all your questions.