Are You Ready?
By E.L. Squires, M.S., Ph.D., hon, ACT, Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, Colorado

It seems as though, right after the first of the year, every equine breeding farm becomes extremely busy, as well as the veterinary clinics. Every breeding farm essentially has three groups of mares that they have carried through the winter, mares that are to foal, mares that have never been bred (maiden mares) and mares that did not provide a foal last year (barren mares). Each category of these mares requires a different plan.

Foaling mares
The approximate duration of gestations is 340 to 345 days. However, the length of pregnancy is about seven to ten days longer for mares foaling in the winter than for those foaling in late spring or summer.  Mares maintained under lights during the last few months of pregnancy will have a shorter gestation. Pregnant mares should be vaccinated one month prior to their due date to increase antibody levels in the colostrum. If the mare has a Caslick's performed on the lips of the vulva, they should be opened approximately two weeks prior to the expected time of foaling.

Some indication as to how close a mare is to foaling includes milk calcium levels and waxing of the teats.  There are several commercial test kits available for measuring milk calcium.  These appear to be fairly accurate in that most mares have an increase in milk calcium levels above 200 parts per million within 48 hours of foaling.  Waxing of the teats is also an indication of imminent foaling.  This usually occurs 24 to 48 hours prior to foaling.  However, not all mares wax up and the duration of waxing can be quite variable.  Waiting for a mare to foal can be extremely tiresome, but devices such as Foal Alert and cameras in the stall can be extremely helpful, as well as the milk calcium test.

Once a mare foals, it is extremely important to make sure that the foal is breathing properly.  This may entail the removal of the amnion from the nasal area.  It may also require stimulating respiration by rubbing the newborn foal with a towel or extending the front limbs to stimulate activity. The navel should be disinfected shortly after foaling to prevent bacterial infection.  The common disinfectants used include Nolvasan, Betadine and Iodine. It is recommended that the navel be dipped two or three times per day for the first two or three days after birth. The foal should stand and nurse within approximately one to two hours after birth.  Ideally, a liter or more of good quality colostrum should be ingested by the foal within the first six to 12 hours of life. Antibody levels in the blood of the foal can be checked 24 to 36 hours after birth to determine if adequate transfer of colostral antibodies has occurred.  The mare should pass the placenta within three hours after foaling.  Failure to pass the placenta could lead to severe medical conditions in the mare, such as laminitis.

Maiden mares
Maiden mares are those mares that have not been bred during the previous breeding season. One of the things that can be done to prepare these mares for breeding is putting them under an artificial lighting regime beginning December 1.  These mares can be placed under an artificial lighting regime either in a paddock setting or in individual stalls. The amount of light should be bright enough to allow you to read in any corner of the stall or paddock. It is suggested that the additional light be provided in the afternoon or evening rather than in the morning.  Thus, mares can be turned out during the day, brought back in before dark and additional light added in the afternoon and evening to make up a total of 16 hours of light. It will require approximately 60 days of long days in order for the mare to be stimulated to cycle.

It is also important that the mare be in good nutritional condition. It was once thought that mares should be brought into the breeding season relatively thin, and then fed an increasing diet to gain weight.  Based on numerous studies, it appears to be more effective if the mare is brought into the breeding season in good to almost fat condition. In the long run, this may be more economical than having the mare come in thin and trying to increase the weight of the mare during the time of breeding.

Generally, if one is going to breed mares early in the year, then teasing the mare with a vigorous stallion begins either daily or every other day approximately 30 days prior to the time of anticipated breeding. In addition, on most major breeding farms, mares are examined with ultrasonography to determine the presence of a large preovulatory follicle. Unfortunately, mares do not make a smooth transition from winter anestrus (small, inactive ovaries) to normal cycling. They experience what has been called a transition period.  During the transition period, the mare may have long, erratic periods of heat that may extend 10 to 20 days. Also, during this transition period, follicles on the ovary tend to grow and regress without ovulating.  This makes it very difficult to determine when the mare should be bred. Thus, the tools of teasing and ultrasonography are helpful in determining when the mare should be bred during the transition period.  Another helpful tool is to place a transitional mare on ReguMate (progesterone treatment) for approximately two weeks. This suppresses the occurrence of estrus and assists the mare in establishing a normal cycle earlier in the year.  At the end of the two-week progesterone treatment, on would anticipate that the mare would come into estrus and ovulate in a more predictable manner.

Barren mares
Barren mares are those that either failed to become pregnant during the previous year or became pregnant and lost the pregnancy. Treatment of these mares is quite similar to what has been described for the maiden mare, except that one should try to determine the cause of infertility prior to rebreeding the mare. This may require that the mare be given a complete reproductive evaluation. Generally, the best time to evaluate barren mares is at the end of the previous breeding season when they are still cycling.  However, if they happen to abort during the fall or winter, then it is best to conduct the reproductive evaluation this breeding season once they have established a normal cycle.  The breeding soundness examination should include a complete palpation of the reproductive tract, as well as an ultrasound exam of the reproductive tract. In addition, one should take a culture of the uterus, cytology of the uterus and a biopsy of the uterine lining.  These techniques will provide some information as to whether or not the mare is infected or whether or not the mare is capable of establishing and carrying a pregnancy to term.

Probably one of the most important keys to a successful breeding program is a good working relationship between the broodmare manager, stallion manager and veterinarians. Communication amongst these individuals early in the breeding season is essential to a successful breeding program.

About the Author...

E.L. Squires, M.S., Ph.D., hon, ACT

Animal Reproduction and Biotechnology Laboratory

Colorado State University, Fort Collins, Colorado

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