Vet Talk

On Shaky Legs: Another Look at Foaling Season, Part 2 – Breeding and Gestation

You know it's not going to be that easy, right?

March 10, 2014 (published)

You’re ready to sit back and let nature do the rest. Someone wake you when the foal comes. Sound good?

You know it’s not going to be that easy, right? There’s still plenty of work: for you, your mare (not to mention the stallion), and your veterinarian. This part will take some time and patience. There are plenty of resources that will give you nicely detailed step-by-step guidelines for equine breeding. This isn’t one of them. You can research the details of the mare’s estrous cycle and timing of insemination by yourself, and I recommend that you do. But, like with human sex, reality and the textbook don’t always look exactly alike.

But you can, so light some candles, put on some good music and let’s get to it.

1. Pre-Breeding Exam
The pre-breeding or breeding soundness exam (BSE) may seem like it stands for (Expensive) B.S. After all, your mare is healthy. She’s young. Or she’s had a few foals. Anyway, you know she’s fine. After all, what do horses in the wild do? It’s not like there’s a veterinarian standing by with a speculum and an ultrasound while the mustangs are getting busy.

However, you’re paying to breed her to a (hopefully) genetically superior stallion, not turning her out with that feral herd. And you don’t have a vested interest in the healthy reproduction of those hypothetical wild horses. While it’s human nature to avoid spending money unnecessarily, it’s also human nature to protect our investments. You wouldn’t buy a Bentley and then stick it in the garage with the kids’ bikes and the camping gear, would you?

A BSE involves a thorough evaluation of the mare’s reproductive tract by looking at the ovaries and uterus via ultrasound, examining the vagina and cervix with a speculum, and taking swabs of the uterus to check for abnormal cells and to culture for bacteria. This exam allows the vet to diagnose and treat any conditions, such as inflammation or infection of the uterus or cystic ovaries, that may make it difficult for her to conceive or maintain a pregnancy. It also lets you know if a mare may have a condition that would simply not make her suitable for breeding at all.

Skipping the BSE can lead to a Happy Now, Sad Later situation.

2. Timing
In reproduction, as in theater, timing is everything. Successfully breeding a mare isn’t just a matter of sticking mare and stallion together or ordering some semen and shoving it “in there” with a turkey baster.

The equine reproductive system responds to increasing daylight. This means that the horse is not typically fertile year round. (No, that’s NOT an invitation to turn that intact colt out with the fillies in the winter! Stuff happens.) The natural breeding season for the mare runs from early March through June in the Northern Hemisphere. But we humans like to mess with mother nature, and trying to get ever closer to that coveted January 1 birthdate so that young horses will be bigger and stronger than their competition, breeders use artificial lighting to bump the breeding season earlier. This means if you wait until late May to decide to breed your mare, you may have missed the reproductive boat, since many stud farms quit collecting semen from their stallions by June.

Mares ovulate or kick loose an egg from the ovaries every 21 days or so. (Pay special attention to the “or so.”) The egg is inside a bubble called a follicle, which gets larger and softer until it essentially bursts. Ta-Da! Ovulation!

The candles-and-slinky-lingerie period (estrus or “heat”) for the mare lasts for roughly 7 days around the time of ovulation. In theory, she ovulates somewhere around day 5 of that phase.

Here’s the problem. Horses don’t know how to read. Some of them just don’t follow the instruction manual. A mare might ovulate on day 3 of her heat cycle, or she may play coy and not show any of the typical signs of heat. Or, and this tends to happen in early spring, she may develop the proper structures on her ovaries but not ovulate at all that cycle. She may even defy all logic and decide to ovulate over a holiday weekend. FedEx doesn’t care that your mare is ovulating; they won’t change their schedule just to ship semen to your horse.

Even if you’re breeding the stallion to the mare directly, timing still matters. From a behavioral standpoint, the mare has to be ready, or the entire venture isn’t only a waste of time, but it’s potentially disastrous to the stallion’s fragile assets. Male genitals tend not to fare well when struck with a hoof.

Also, unless you are boarding your mare at the breeding farm for the entire season, you need to know when to take her.

So no matter what breeding method is being used, you need to know when the mare is most likely to ovulate. You can get an idea of her point in the estrous cycle by checking for behavioral signs of heat. (I’m not going to list them all here; go do your research!) But in order to narrow the window to the 24 hours or so when you want the sperm and egg to be in the same vicinity, you need to know how fast the follicle is growing, its consistency (just before ovulation, follicles get squishy like a Jello shot), and its size. The best person to check these variables is your friendly neighborhood veterinarian. “Follicle checking” a mare involves arm-into-rectum intimacy with the mare which, if done incorrectly, has the potential to injure or kill both the bearer of the arm and the owner of the rectum. This brings us to…

3. Veterinarian
If you decide to breed your mare, plan on getting to know your equine veterinarian intimately. This is the person you’ll be seeing and whose advice you’ll be taking for the next 11 months or so, who you’ll have on speed dial, and whose bad hair days you’ll come to know well.

Not all horse docs relish repro work, so talk to your regular vet well in advance about this breeding thing. Make sure he or she will have the time, availability, equipment, and interest to do what you need. Speaking as a vet, there is nothing worse than having someone show up assuming you can make their dream come true with no prep work and insufficient time in the schedule or facilities.

Ideally, your veterinarian knows you and your mare well, and can help steer you away from any spike-lined pits that might be lurking along your road to foal production. Get estimates of expected charges before you ever begin the process; have a frank discussion about your budget, and about what unexpected (and potentially expensive) circumstances your veterinarian might foresee. Breeding and monitoring a pregnant mare can take a lot of veterinary time. Be prepared to pay for that time and expertise.

4. Type of Breeding
I’ve alluded to the fact that there’s more than one way to build a foal. Foal conception comes in roughly four styles:

a. Natural Breeding or “Live Cover:" this is the standard birds-and-bees, old-fashioned method. Stallion meets mare, stallion mounts mare, mare and stallion both leave happy, hopefully foal ensues. Thoroughbreds are only bred via natural cover.

b. Artificial Insemination (AI) with fresh semen: In breeds other than the Thoroughbred, this method is the most common. AI allows one stallion to breed multiple mares with a single ejaculate, keeps the stallion (and his jewels) out of harm’s way, and enables mare owners to breed to a stallion located anywhere in the country.

Timing matters with AI. Over the course of a season, the stallion and his swimmers get tired. To keep from having a worn out shadow of a formerly studly horse by the end of the spring, stallion managers only collect semen on specific days of the week. Additionally, fresh semen, while packaged with special sperm “food” called semen extender, has a limited shelf life. Generally you’ve got about 48-72 hours for the sperm to meet the egg, take her for coffee, and get down to business.

c. AI with Frozen Semen: frozen semen has a longer shelf-life than fresh, BUT only while it is frozen. This also allows longer distance shipment of semen. However, since it can be a logistical pain in the nether-regions, AI with frozen semen is far less common than with fresh. Once semen is thawed, those sperm are not long for the world. The window between insemination and ovulation can be measured in minutes. Generally the mare needs to be bred within an hour of ovulation. That means that someone has to monitor that follicle around the clock for a good 12 to 24 hours. That’s a lot of ultrasounds, folks!

d. Embryo Transfer (ET): This is the most expensive and technically demanding route, by a long shot. Think of ET as the “expert drivers on a closed course; don’t try this at home” method of horse breeding. ET is generally used when a mare has fabulous genetics but isn’t suitable for carrying the foal, either because of age or some medical issue, or because she is performing at a high level. In this case, her eggs are collected, fertilized in vitro (meaning in a petri dish) and implanted into a recipient mare who then carries the foal to term.

5. Mare Care
With all of this focus on creating a foal, it’s easy to lose sight of the animal making the entire venture possible: the MARE. I have seen owners say “Eh, she’s just a broodmare,” and turn her out in a pasture after breeding with no thought to dental care, hoof care, vaccinations, handling, grooming, or nutrition. Don’t be that person.

Here’s the thing. Your broodmare is going to be growing an entire other horse in her uterus. She needs better nutrition, which also means better dental care. She will be bearing  more  weight on her feet; that means she needs regular hoof care. Assuming you’d like that foal to be born healthy and disease free, she needs an enhanced vaccination and parasite prevention program. And while grooming and handling may seem like frills, think of it this way: do you really want her first human contact in nearly a year to be when something large is trying to escape from her vagina?

That dental you’ve been putting off? Get it done before you breed her. Schedule routine hoof trimming appointments with your farrier. Talk to your vet about vaccines, parasite control, and feeding. Get your teenager away from the gaming console and have him brush the horse every so often.

That was a long post, and thanks for sticking around. Just remember, it’s all part of a much longer journey. Stick around for part 3, where we’ll take a look at the BIG DAY, and what lies beyond.

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