Including avoiding raccoons, playing Cupid for the teaser, and testing mares for pregnancyApril is the cruelest month, breeding

Lilacs out of the dead land, mixing

Memory with desire, stirring

Dull roots with spring rain.

-from "The Wasteland" by T. S. Eliot



The conventional harbingers of the season for most normal folk are the first daffodils, the brilliant sprays of forsythia, the greening of the fields, and that subtle quickening of the pulse that signals "spring fever." I see all these signs, but there are a few others that especially mark the end of winter for me.

My teaser, even though this marks his third frustrating month of unrequited love, trots from barn to barn with a noticeable extra spring to his step. As he canters along, Peashooter sounds his macho "I'm feeling lucky" neigh. Perhaps he dreamed my shank broke, or that someone left the gates open on both his and the maiden mares' paddocks. But, more likely, Peashooter's renewed vigor is the result of the effect the increasing photoperiod has on stallions, as well as mares. In stallions, the testicles actually grow considerably in size as the season progresses. The difference in size and fertility is marked, which led some farms to experiment with lights to accelerate the process in their stallions and perhaps increase the number of mares the stallions could cover. But the method was abandoned when it was found that it led the stallions to reach their peak too soon in the season, after which they began to tail off, just at the time (mid-April to mid-May) the most mares needed to be covered.

This increase in testicular girth can actually be monitored using a pair of special calipers developed at Colorado State University. Looking like a pair of blue plastic ice tongs, the calipers are relatively easy to use on a cooperative horse, which most become if the handler is understandably considerate. They have been in use at several stud farms to monitor the reproductive health of their horses, but I am going to depend on more subtle behavioral signs to reflect Peashooter's reproductive health.



Muskrat love

Another sure sign that spring has arrived is seen in the phenomenal number of raccoon couples lying dead at the side of the road. Actually, the carnage began a few weeks ago when you could not drive a mile without being reminded of the potency of skunk musk. Then, possums had their numbers decimated by passing traffic, and now it is raccoons. So many line the backroads, it would be possible to collect enough for a coat in about ten miles of driving. (To prevent being spattered with red paint by some rabid animal rights activist, it might be wise to have a large label saying "100% Kentucky road kill" or words to that effect. There may be a new cottage industry here.)

Having read Rascal as a child, I have a fondness for 'coons, in spite of the fact they are the primary vectors for rabies in our area. Still, there is a certain poignancy in seeing a raccoon couple so lost in their ardor (to the strains of "Why don't we do it in the road?") they fail to register the danger posed by an oncoming car. But why so much activity near the road?

Perhaps the answer lies in a curious human analogue to this odd phenomena that occurs in rural southern areas. This "lying-in-road syndrome" usually occurs on Saturday nights when some poor farm hand goes home after a night of drinking. Tiring of the walk, they often decide to take a little nap. The roadway retains the sun's heat and so they pause-permanently, if their presence is not noted in time by an unsuspecting driver. Though not exactly a leading cause of mortality, it happens enough in some counties to actually have a name. Maybe the skunks, possums, and raccoons are also drawn by the comfort offered by the warm, dry pavement over the cool, wet grass.



Pregnancy puzzle

Spring also finds us examining mares on an almost daily basis for pregnancy. Twenty years ago, it was common to wait until the 36th day after a mare was bred to palpate her for pregnancy. This was fine if she was pregnant, but meant you had lost a full cycle if she was not. Also, if it turned out that she was carrying twins, pinching one often resulted in the loss of the other. And twins could only be detected if they were in opposite horns of the uterus. Those in the same horn were usually undetectable to even the most skilled veterinarian.

Then the ultrasound was introduced for equine reproductive work. Following research done by Dr. O. J. Ginther at the University of Wisconsin, area practitioners were finally able to "see" what their hands were feeling. At first the practice which did our work had only one machine-a big, awkward affair-so we actually would put all of the mares we wanted to check in one barn to facilitate the examination.

It was expensive, so not every mare was examined at first, only those who either had a history of twinning or had been bred on double follicles. Genuine Risk, Bold 'n Determined, and Candy Eclair all had been retired to the farm that year and, naturally, they were included in these initial examinations when their turn came. But a curious thing occurred. An amazingly high percentage of the mares (including each of the Big Three) were found to be carrying twins at 15 days. Fortunately, "embryo reduction" was relatively easy in most cases, and it became clear that in capable hands, twins could be largely eliminated as a problem.

Further research found that many of the twins that occur in the same horn would have spontaneously resolved themselves. One of the embryonic vesicles would have more contact with the uterine wall than the other, grow faster, and, finally, the small one would, in effect, starve to death. This is why the incidence appeared so high. Most would not have resulted in twins, even without human intervention. However, some would. And, occasionally, both would perish later in the pregnancy. So once you were aware that this had occurred, it became necessary to look at everyone, because it is a well known axiom that these problems will occur in either your best mare or the one bred on the no-guarantee season.

To further complicate the problem, the chance of separating and successfully pinching twins is lessened considerably beyond day 16 after breeding. Since most mares are on a 17-to-18-day cycle from heat to heat, you are forced to check mares that may show heat the next day if you could wait. This means that you have to spend $60 to check every mare, even though some will not be in foal.

While $60 is not much compared to the value (hopefully) of the mare and resulting foal, I would still bend over to pick up $50. And now, thanks to recent advances in assay technology, it is possible to identify those mares who are not in foal with a simple, inexpensive stall-side test.



Right on target

While progesterone assays have been available for some time, it is only recently that kits (Target Equine Progesterone Kit, BioMetallics, Princeton, New Jersey, 1-800-999-1961) have become available that allow the tests to be run on the farm. That means that the test can be performed before the veterinarian arrives and can give the manager one more piece of information on the mare. Using four drops of the mare's blood, it is possible to see in about ten minutes if her progesterone levels are above or below certain levels.

Normally, when a mare is in estrus, her progesterone levels are below one nanogram. After she ovulates, the site on the ovary where the egg was located forms a structure called the corpus luteum (CL). This CL begins to produce progesterone, which, in addition to causing the mare to stop "showing" heat, also tones up her uterus and prepares it for the fertilized ovum. As the days progress, progesterone levels rise and, if the mare is in foal, various chemical signals will tell the CL to continue to produce progesterone. However, if the mare is not in foal, then the uterus will begin to produce prostaglandins which will cause the CL to regress, progesterone levels to fall, and the mare will come back into heat.

The assay does not directly tell you if your mare is in foal. It only identifies those mares whose progesterone levels have fallen below one, and thus are not in foal. There are some mares who may be "spurious" (i.e., they think they are pregnant, but they are not), who will still have elevated levels of progesterone. But this method does eliminate those mares who end up showing heat the next day. If the test shows that her levels are below one nanogram, she definitely is not in foal. The test costs less than $10 and, with a little practice, can prevent some unnecessary ultrasound exams.