Series: Breeding For Newbies Part II

BREEDING FOR NEWBIES

In part one of our Breeding for Newbies series we began laying a foundation that can help set us up for success during this year’s breeding season. In part two of the series, we’ll address the actual process of breeding our mare.

MAKING THE TRANSITION For the mares left to cycle naturally without the accompaniment of artificial lighting, the months of December, January, and February are merely reminders to keep hitting the snooze button on their estrous cycles. While

the days are slowly growing longer, the length of daylight has not yet reached sufficient duration to inspire changes visible to the human eye.

Under the influence of extended artificial lighting since late autumn, however, the mares scheduled for earlier breeding have been led to believe that spring has arrived, and their ovaries are waking up. By late January, these mares are often leaving anestrous behind and entering their transitional heat.

Anestrous is the period of time that a mare stops cycling during winter. Before breeding can occur, we need the mare to shift gears back into an active estrous cycle. The transitional heat acts as a bridge between the two. The first heat of the new season, the transition isn’t fertile in most cases. It tends to be irregular, lasting anywhere from just a few days to two weeks or even more. The ovaries, having not fully revived from their winter slumber, tend to produce multiple small follicles that don’t quite mature enough to be fertile. Later, after the transitional heat has occurred, the ovaries will produce fewer follicles, and one from each cycle will take the lead and mature to ovulation. Once the transitional heat has passed, the mare’s breeding season has officially begun. It is important to stay the course at this point with the artificial lighting, as any sudden changes, especially in decreasing the hours under lights, can cause the mare to revert back to anestrous again.

ROCKING & ROLLING

Early February marks the traditional beginning of breeding season, so by that time it’s a good idea to begin checking the mare’s reproductive status in earnest if an early foal is your goal. If you have multiple horses, you may see her showing signs of estrous to her pasture or barn mates, particularly to geldings. These include frequent squatting, urinating, and “flagging” the tail. Some mares are much more subtle, however, or may show no signs at all, especially if there is no other horse for them to socialize with. A reproductive exam by your equine veterinarian is the definitive way to establish exactly where the mare is in her cycle. Using rectal palpation, ultrasound, or both, the veterinarian will be able to ascertain some key information. Uterine tone and edema pattern, as well as the condition of the mare’s cervix all play important roles in determining readiness for breeding, but if there is a celebrity of the mare’s reproductive tract, it’s the follicle. Perhaps the easiest piece of the breeding puzzle to understand, the follicle understandably receives much emphasis. Follicular size is measured in millimeters. It will increase in size an average of 3mm to 5mm per day until mature. The minimum size a follicle is generally considered breedable is 35mm but measurement is not the only consideration for breeding. As it matures and nears ovulation, the follicle will also soften considerably and its edges will take on an irregular appearance.

BREEDING THE MARE

We want to breed the mare as close to ovulation as possible, so all the key players must come together in concert to have the best chance for a successful breeding. One last option to improve our odds is the administration of a drug to help induce ovulation timed closely to insemination. There are several brands available, but deslorelin or human chorionic gonadotropin (hCG) are commonly used.

Once it’s determined the mare is ready for breeding, then it’s time to contact the stallion manager to arrange a shipment of semen. There are a few key things to know:

Your Balance – what do you owe on your breeding (if anything)?

Cost of Shipments – It’s a great time to re-familiarize yourself with the fee schedule so you’re not caught off guard by shipping costs.

Collection Days & Cutoff Times – Make absolutely sure that you know what days your sire of choice is collected, as some farms stick with a Monday-Wednesday-Friday schedule, while others rotate odd days and even days each month. Find out when, contractually, you are obligated to let your stallion owner/manager know that you are in need of a shipment and by what time you need to finalize those plans.

Once the delivery of semen has arrived, your veterinarian will recheck the follicle, and determine the best course of action with regard to insemination.

In an ideal world, breeding our favorite mare would be a one and done proposition. Sometimes that’s just not in the cards for some reason or other. If your mare does not conceive on the first go around, your vet will likely attempt to short cycle her using Lutalyse or estrumate, and the cycle repeats.

If all the stars align and luck is with us, the 14 day pregnancy check will herald in Part III of our Breeding for Newbies Series, wherein we begin our long wait for our future superstar.