The ultimate goal of every breeder is for each mare to produce one live foal each year. However, as in most species, reproductive efficiency declines with age. By the time a broodmare enters her late teens and early 20s her ability to reproduce begins to diminish, and getting and keeping her pregnant become more problematic. Older mares have about a 30 percent chance of becoming pregnant and need to be bred twice as often as younger mares.
The most likely causes of reproductive difficulties in the older mare include poor uterine clearance, anatomical defects involving the reproductive tract, contamination, infection, aged eggs, overzealous use of antibiotics, cysts, ill health, lack of fitness and poor nutrition. Your veterinarian will need to make an accurate diagnosis of the cause of infertility in order to administer a therapy most likely to produce optimum results.
According to John Dascanio, VMD, Virginia-Maryland Regional College of Veterinary Medicine, a reproductive examination should start with evaluation of conformation (the uterus could be tilted, for example) and natural barriers that normal keep infection away. You or veterinarian should also examine the reproductive tract by palpation and by ultrasound examination. Following that, your veterinarian should examine the vagina and cervix with a vaginal speculum and manual exam. This may be followed by a uterine culture, cytology (microscopic study of cells) and biopsy, which can help predict the mare's chances of getting pregnant.
Should preliminary results turn up normal, other specialized tests can be performed. Your veterinarian may want to examine the oviduct (the passage through which the eggs move toward the uterus) to make sure it is clear. He or she may also want to test for anti-sperm antibodies, assess your mare's hormonal status and check for chromosomal abnormalities. These procedures may require special equipment or facilities and may not be done on the farm. Diagnostic information can even be gained from frequent ultrasound examinations, such as looking for fluid accumulation with the first day post breeding to help diagnose uterine clearance problems.
Treatments vary from simple to high-tech.
Anatomical defects of the vulva, vaginal fold, and cervix can be corrected surgically. These surgical procedures include cervical reconstruction, urethral extension and Caslick's procedure.
To improve uterine clearance, mares can be treated within hours after breeding with saline lavage. This can be followed by the use oxytocin (a naturally occurring hormone that causes uterine contractions during labor) or a prostaglandin product, which is commonly used to bring a mare into heat but which also helps contract smooth muscles, to help increase muscle contractions within the uterus in order to dispel more fluid.
Exercise and keeping the mare near a stallion also could improve uterine clearance. Hearing and even smelling the male can sometimes help to improve tone in the reproductive tract.
Antibiotics might be introduced early in the heat period if an infection is confirmed via a culture and cytology. However, whether you use antibiotics depends on your specific situation.
Assisted reproductive techniques are available for those willing and able to invest in more advanced technologies. These include embryo transfer, GIFT (oocyte or gamete intrafallopian transfer), and in-vitro or ISII (intracytoplasmic sperm injection). These all utilize the oocyte from a valuable mare but use a recipient mare as a surrogate to carry the pregnancy. This is mostly helpful if the mare has an anatomical problem.
Common Sense Techniques
Good management and sensible, careful breeding techniques can also go a long way to improving the older mare's chances of pregnancy. Here are a few tips:
Use clean breeding techniques. Consider artificial insemination instead of mating. Wash the mare's vaginal area and examine her for contamination in the vagina. Use filtered semen with antibiotics and breed her in as sterile manner as possible.
Use good timing. Allow sufficient time after a previous foaling for your mare's reproductive tract to get back to normal shape. And time the breeding so she only has to be bred once instead of invading the reproductive track several times during a single heat.
Make sure the stallion is a good candidate by having his sperm tested. The ideal stallion has live sperm with good longevity and is free of harmful organisms.
Maintain a quality health maintenance program for the mare. This includes a good vaccination program: rhinopneumonitis at 5, 7 and 9 months of gestation; annual influenza; tetanus and encephalitis boosters preferably at 10 months gestation; regular deworming; and dental and foot care. She should have plenty of exercise, proper diet and routine physical examinations. Proper evaluation will correct many problems before they start and give your mare a much better chance of success.