Ron Friedman, MS, DVM, Dipl. A.C.T.
Part II: Last month we discussed ways to prepare your mare for the breeding shed by helping her to cycle early. This month we'll compare different breeding methods to help you make the best breeding decisions for your mare. In addition, we'll discuss the use of uterine cytologies, cultures and several ways to improve the chance of getting your mare in foal.

A factor to consider when breeding any mare includes how to breed her. The different methods of breeding horses include live cover and artificial insemination (AI). Live cover can be accomplished by pasture breeding or assisted breeding with handlers on both mare and stallion. With Al, the stallion's sperm (fresh, cooled/shipped, or frozen semen) is placed in the mare's uterus by a veterinarian.

Some farms will ship semen to you; others require that the mare be transported to the stallion. If you transport your mare any distance it is usually necessary to leave your mare at the breeding farm until she is confirmed pregnant. With any history of pregnancy problems you should probably leave your mare there until after 40 days of pregnancy.

When using live cover breeding there is always the risk that one horse may kick or bite the other (or a handler) during the breeding process. Experienced handlers can minimize this risk, but as you well know, with horses anything is possible. With pasture breeding you leave it entirely to the horses. Although this method has worked for thousands of years it is only rarely used by breeding farms today because of liability and other obvious concerns.

Artificial insemination with shipped semen offers the opportunity to breed to stallions who otherwise would be unavailable because of their location and activities (showing). Both Al and transporting mares to the stallion have their associated costs, but if your mare and the stallion are fertile, shipping semen can certainly be more convenient.

Assuming good stallion fertility (bad assumption, but one we'll make for the sake of easier discussion) of all the breeding methods, Al of fresh semen can result in the greatest success, followed by natural cover, then Al of chilled semen, and finally frozen semen.

An inevitable cost to owners using shipped semen arises from multiple palpations and inseminations over several cycles. To keep these costs down, it behooves you to be certain your mare is cycling regularly and is free from uterine inflammation or infection early in the season and before you start breeding. It is disheartening to examine a mare for pregnancy after her second cycle and discover she has a uterine infection or some other problem. When this happens we are under the gun, so to speak, because it will require getting the mare back into estrus, taking a culture and treating her.

Sometimes we can't breed these mares until the cycle after treatment, and before you know it, the end of breeding season is near. Remember, in many stallion operations we only have 137 days in the breeding season! I think you can see why we want mares who will be getting shipped semen cycling early in the season and free from inflammation or infection!

As discussed above (and in last month's article Prepare Your Mare for Breeding), in addition to early regular estrous cycles, another major goal of prepping mares for the breeding shed is to have them free of uterine inflammation or infection. This is accomplished with uterine cytologies and cultures. When breeding your mare you'll often hear about these common procedures. These techniques, which look for the presence of intrauterine bacteria and inflammation, are frequently requested by stallion managers who utilize live cover or shipped semen. While many veterinarians, including myself, find cytologies more valuable than cultures, cultures are more frequently requested.

Cultures and cytologies can be advantageous to both the mare and stallion owner. The stallion owner wants to decrease the number of "wasted" breedings on mares who can't get in foal because of infections and other problems. By "weeding out" these mares they reduce the number of times a stallion must be bred or collected and the number of times a problem mare will be bred. Cultures and cytologies also reduce the concern of spreading sexually transmitted diseases in horses. Fortunately, venereal transmission is rare in the horse.

In fact, a stallion is more likely to contract genital infections from having his penis washed excessively with soap, than through sexual contact.

Regarding the culture of maiden mares, this practice is questioned by many because uterine infections in them are virtually unheard of. Overall, this standard policy of culturing all mares is a good one because it helps to screen out the mares who won't settle without some initial help. Also, it could take a tremendous amount of time to confirm if a mare was maiden or not. The easiest answer for the stallion owner is to culture all mares.

As we have emphasized, early prepping prior to breeding will work to your advantage. When a problem is found, the earlier in the season it is corrected, the more time you have to get your mare in foal. Other diagnostic methods for preparing a mare for the breeding shed include rectal palpation, speculum exam, biopsy, ultrasound, endoscopic exam of the uterus, and hormonal analysis. Those subjects are best covered in another article because of their depth.

On a related note, in addition to lights for mares, work has been done to look at Melatonin and GNRH to manipulate cycles in horses. Melatonin is a hormone which has gotten lots of press lately because of its many claims, one of which is to help people sleep. In horses Melatonin has been used to simulate short day cycles. (Kind of approaching the estrous/anestrus subject from the opposite end.) Lights shorten anestrus and hasten the onset of estrous. Melatonin, if given in mid summer, shortens estrous and hastens winter anestrus. Once properly exposed to short days, the mare can then respond to lights or the stimulus of long days. Consider this therapy if you find your mare not pregnant this summer. If such a mare was given Melatonin at that time, followed by lights next November, regular cyclic activity could be achieved early next season.

Beginning in the 1980's, researchers used GNRH (gonadotropin releasing hormone) to attempt to shorten anestrous. Studies tested the possibility of using this hormone to bring continuously anestrous mares into estrous. Unfortunately, the results have not been promising. Some common problems included the frequency of dosage (hourly or implants), expense, and a frequent result that if estrous and ovulation were induced, removal of GNRH would result in the mare going back into anestrus.

Finally, let's discuss a few general breeding ideas which help fertility and should be incorporated into all breeding programs, when possible. Our first suggestion is to tease the mare (expose her to a stallion). Not only does teasing help detect estrus, but research strongly suggests that regular exposure to stallions via teasing helps some problem mares ovulate better. Second, consider using fresh semen if you have an infertile mare. Fresh semen and Al, as mentioned earlier, can increase fertility. Third, breed the mare as few times as possible, as close to ovulation as possible. Breeding after ovulation, unless one knows with certainty that it was less than six hours ago, is often unsuccessful. New semen extenders can increase the success of post-ovulation breeding, but this method should not be your first choice. Finally, if more than one breeding per cycle is needed, it's clear that breeding every other day is better than every day! Breeding every day can decrease fertility.

We hope we have been able to show some of the benefits of preparing your mare prior to the breeding season. Establishing early, regular cycling prior to having your mare bred is especially important for problem mares, performance and show mares, and any mare bred by shipped semen. Because of the short breeding season available to many mares, it is a good idea to have them cycling early and free of infection, so that if a problem is uncovered there is sufficient time to address it.

Although we've tried to keep things simple, the details can be complex and confusing when dealing with a problem mare. The more you know before you begin breeding, the better prepared you'll be to make sound decisions. If you have questions after reading this article, call your veterinarian or please feel free to call or e-mail our office. Good luck in the coming breeding season!