What to do with the 'leftovers'

What to do with the 'leftovers'

Finding reasons for last year's non-breeding mares a priority this time of year
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Feb 01, 2004

This is an appropriate time of the year to be thinking about leftovers.

First there was all that Halloween candy. Then turkey, dressing and cranberry sauce and the days and days of turkey sandwiches that followed.

We all overindulged a bit over the Christmas/Hanukkah holiday and there are still likely some cookies left about. If you look really carefully you may even find the last remnant of leftover fruitcake.

For some equine veterinarians, though, the holidays have a bit of a different significance and "leftovers" are not something to be anticipated.

Problem maresThanksgiving Day is traditionally the day that many breeding farm managers start increasing the amount of artificial light that their broodmares are exposed to. This increased lighting will help these mares start cycling early in the upcoming year.

The fact that these mares need to cycle early so that they can be bred means that they did not get bred this year and that usually means that they are "problem" mares.


A thorough reproductive exam is the first place to start with any mares that have had breeding or foaling problems in the previous season. Uterine culture, cytology and ultrasound examination will provide a wealth of information and other diagnostic exams such as uterine biopsy and oviductal analysis may also be needed.
These horses either did not cycle correctly through the year or they developed uterine infections that could not be cleared up or they were pregnant and aborted or any number of other problems occurred to keep them from settling. These are the "leftovers" and for the reproductive veterinarian they represent the past year's failures. The early part of the New Year is the time for dealing with these mares so that they are ready to go when breeding season comes around.

No rest for wearyAfter a busy foaling and breeding season and then weaning, then show season which now stretches until the very end of the year, most equine veterinarians get to the holidays and want to rest a bit, watch their favorite teams play on Sunday, go hunting and basically do anything other than more work.

But this time of year is the best time to concentrate on these problem mares and to develop a strategy that will turn these past failures into potential successes. New developments in hormonal therapy, correct nutrition and advances in the treatment of equine uterine infections can be of help. Simple attention, during the winter, to all the details involved in creating a successful breeding may lead to clean, healthy mares for the spring and that can be the beginning of a very happy New Year.

First stepThe first step in dealing with the "leftover" mare is to perform a complete breeding soundness exam.

This is a popular topic at this time of year and any number of references can be found for such an exam.

The first step in the exam is to review the past year's breeding records. Complete and accurate teasing and breeding records are crucial to a successful breeding operation and, by critically examining this data, you may be able to get your first clue to the particular problems experienced by each mare.

Often during the breeding season it is difficult to see patterns for individual mares since the primary concern is that particular current cycle.


There are many reasons why a mare may be non-pregnant or open at the end of the year. Failure to conceive after three or more covers, uterine pathology including infection, cysts or persistent uterine fluid are among the most common reasons. Abortion from a variety of causes will also result in open mares entering the breeding season. Aborted fetuses should be carefully evaluated in order to determine a possible cause.
But overall details may be more easily seen on a later general review. Did a certain mare take longer than normal to return to estrus on more than one cycle? Could she have a hormonal problem that needs to be investigated? Did a particular mare culture clean but consistently show small amounts of uterine fluid for a few days post-ovulation? Does she need lavage and Oxytocin injection following breeding?

Examination of well-kept breeding records can be very helpful in determining factors involved with problem mares and this review should be your first step.

StallionThe next step involves the stallion.

Breeding problems are traditionally blamed on the mare, at least initially. But many stallions can be the source of problems in a breeding program and stallion records should be reviewed as well.

Did the stallion show consistently good numbers of sperm and good motility? Did he have an acceptable conception rate, and are many of those mares still in foal? Did the stallion experience a drop in output or motility for a brief period of time during the season? Were semen cultures done periodically during the season?

The mares that can provide the most information about a stallion are the mares that he did not get pregnant. Were any open mares related? Is there any sort of a sperm incompatibility problem? Were most of the open mares older or younger, thin or heavy? There are so many possibilities that can affect breeding that any and all pieces of information are important.

MareNow the mare in question should be examined. A complete physical examination should be done before the reproductive tract is focused upon. Any abnormalities in other body systems should be addressed.

Routine blood analysis should be done to evaluate liver, kidney, muscle and other body systems. Abnormal white blood cell numbers may point out a chronic infection or immune problem and problems with red cell indices can be evidence of anemia or other related problems. An evaluation of thyroid levels might also be warranted as low thyroid has been correlated to poor reproductive performance.

If the mare in question is normal, then a detailed reproductive exam is next and should include an ultrasound exam and uterine culture and cytology.

A vaginal speculum exam is usually done prior to the ultrasound exam. Examination of the vaginal vault may reveal urine pooling, which can be a significant problem in older mares. The speculum exam is also used to examine the cervix to be sure that there are no tears or lacerations from breeding or past foaling.

Such abnormalities may allow the mare to become pregnant but not to continue the pregnancy past a certain point. The damaged cervix in such a mare cannot function as an absolute barrier between the inner uterus and the outer environment. At a certain point in the pregnancy this incomplete cervix fails and the uterus is traumatized (usually by bacteria) and the mare aborts. Breeding records (conception and subsequent embryo loss on more than one cycle) are important in identifying those mares that may have cervical problems.

Ultrasound examination of the uterus allows a determination of normal uterine anatomy, ovarian size and shape determination and an evaluation of uterine fluid, cysts, and fibrosis (scarring). Thickening of specific areas can be significant. If the mare is examined during a time when she is still cycling then an evaluation of follicle size, numbers and development is also done.

Uterine culturesUterine cultures are done next to determine the presence or absence of bacteria, fungi or yeast in the uterus.

Sterile technique is crucial to avoid confusing the results with contamination bacteria. Cytology of the uterus is becoming increasingly used as a means of placing some emphasis on the culture findings. Positive culture with cytology that shows little to no inflammatory cells is likely contamination.

Negative culture but neutrophils and inflammatory cells suggest an infection that may not culture on standard medium or an inflammatory process without bacterial involvement. Culture can be done using low volume saline infusion and swabbing with a standard culture rod. This rod tip is then rolled on fresh slides and stained with Wright's stain (Diff-Quik) and periodic acid-Schiff (PAS). This combination of stains allows the practitioner to check for bacteria and fungi. Slides are evaluated for the presence of polymorphonuclear cells (PMN) and endometrial cells. Inflammation is felt to be occurring when the ratio of PMN to endometrial cells exceeds 1:40.

Chronic problems and long-term infections may exist with a much lower ratio, but 1:40 is the accepted starting point.

Passing a 20 French balloon catheter into the mare's uterus and inflating the balloon produces a better cytology sample. Sixty ml of sterile saline is infused and the uterus is manipulated by rectum to recover as much of the fluid as possible.