b'8 STEPS FOR BREEDING YOUR MAREKnowing when a mare is in heat is important to determine when the veteri-narian should start examining the mare for follicles, which can help determine ovulation and time of breeding, whether via natural cover or artificial insemina-tion (AI). Macpherson uses a teasing stallion to identify signs of heat in the mare, such as interest in the stallion (especially with head-to-head contact), vulvar wink-ing, squatting into a breeding position (receptivity), tail-raising, and frequent urination. Signs a mare is unreceptive to a stallion include pinned ears, tail-clamping, aggression and striking toward the stallion, and disinterest. For more on teasing, visit TheHorse.com/14717. Step 5: Determine when to breed ARND BRONKHORSTthe mareOnce a mare has started cycling, the owner must decide whether to breed her on the first heatthe less common approach, says Wolfsdorfor wait forOnce the mare has been bred, your veterinarian can confirm pregnancy via ultrasound 14 to 15 days subsequent heats, which have higherpost-ovulation.pregnancy rates. If youre breeding for a potential Thoroughbred racehorse,mine what days the stallions are collectedLets say she has a 25-millimeter however, you want that foal to be born asand shipped and whether theyre shippedfollicle on her ovary when you give her close to Jan. 1the breeds official birthcounter to counter (by commercial air- prostaglandin; its probably going to take dateas possible. plane) or by FedEx overnight, says Wolf- four or five days for her to come into Breeding methodlive cover or AI sdorf. This will help youtime yourheat and another three to four for her also dictates breeding timing. Breedinginsemination using ovulatory-inducingto ovulate, says Wolfsdorf. However, if via AI is partially based on whether youreagents for when you get the semen.she has a big 35-millimeter follicle on her using fresh, cooled, or frozen semen.ovary when you give her prostaglandin, if Fresh semen has the highest fertility ratesStep 6: Use veterinary technology toyou get rid of the corpus luteum (CL, the because its not processed, but it cant betime breeding with ovulation progesterone-producing structure formed transported and must be used immedi- One way to get a mare pregnant soonerafter the follicle releases the egg), that ately. Cooled semen viability is stallion- and/or better track her cycle is to have amare comes into heat in two to three days dependent but is usually good for 36 toveterinarian short-cycle her off the firstand ovulates in (another) two to three 48 hours from collection to insemina- heat post-foaling (aka foal heat), if youredays.tion. With these methods the veterinar- breeding her back. The veterinarian willAn ovulatory-inducing agent, such as a ian should prepare the mare to ovulatedo this by administering exogenous (notGnRH analogue, can also help mare own-within 24 to 40 hours of inseminationderived from the mare) prostaglandinsers predict when to breed. To me, using (see step 6). Frozen semen can be evento bring her back into heat sooner. Thisan ovulatory-inducing agent is just an trickier, because insemination must occurshortens the typical 14- to 17-day diestrusinsurance policy to make sure that they within six hours pre- or post-ovulation(between estrus) period. When the mareare, in fact, going to ovulate when you and, therefore, produces the lowest suc- comes back into heat depends on folliclewant them to, says Wolfsdorf. cess rates. size at the time she receives prostaglandinMacpherson then recommends exam-With cooled semen, you need to deter- (usually six days post-ovulation).ining a mare daily once shes in estrus. Ive learned that I do a much better job if I get to look at the mare a lot, she says. While were focusing on mare management, part of achieving a pregnancyA mare who is not in heat versus a mare involves choosing the right stallion and understanding stallion fertility. Forthat is in heat or a mare that is in early more on how to select a sire, visit TheHorse.com/132564. For more onheat versus a mare thats in her standing stallion fertility, see TheHorse.com/118784. heat (when shes showing full behavioral signs of estrus) can be very different, she says. With a frozen semen mare, were 22December 2019The Horse|TheHorse.comBreedingMares.indd 22 10/31/19 2:21 PM'