Some broodmares do the unexpected during breeding season and during their pregnancy

by Brent Kelley, D.V.M.

I SPENT most of my veterinary career working on broodmares. Most of them went by the book. However, a few of them had not read "the book."

What "the book" tells us, and what we learned in veterinary school, is that a mare has an estrous cycle of 18 to 24 days, four to seven of which she is receptive to the stallion. During these four to seven days, if you tease a mare--expose her to the sexual advances of a male horse--"the book" says she should willingly participate in the foreplay as an indication she is ready to be bred.

Mares cycle in the spring and summer but shut down in late fall and winter. Others cycle year-round. When a mare is pregnant, she does not cycle.

All this is what "the book" says, although I have known several mares that were exceptions to "the book."

Cleaning house

I think all veterinarians who perform broodmare work have sent a mare or two to be bred that have acted up when confronted by the stallion. At least, I hope they have; I would hate to be the only one who has had this happen.

My client purchased such a mare at a November breeding stock sale. She was in foal, so teasing her was not necessary until after she foaled in March and was ready to be bred again. Because she had a difficult delivery, we skipped breeding her on her foal heat, which occurs about ten days after foaling, but we teased her and she teased normally.

Sixteen days after the mare went out of heat, she started to come back in. Everything was still normal. On rectal palpation, I determined she should be bred on day 20, and the farm booked her to the stallion.

Evidently, when she got to the breeding shed, she had a headache. Not only would she not stand to be bred, but she also fought so violently that she was sent home with a message that I needed to accompany her on her next trip to the breeding shed.

I assumed the mare had ovulated before she arrived at the breeding shed, but when I checked her the next morning, I found the follicle was still present. The farm attempted to reschedule her at the breeding shed, but the stallion was unavailable, so we short-cycled her with an injection of prostaglandin to bring her back into heat.

When she came into heat again, she teased fine. I suggested that the teaser jump her before she was vanned to the stallion to see how she would react.

She had a nice follicle, and it seemed that everything was fine. But when the teaser approached her, she blew up.

I had to return to the farm that afternoon for another reason. I asked to check the mare again. She had a nice, almost ovulatory, follicle, so I suggested that we try to jump her again with the teaser. This time she stood.

The manager called the stallion farm and, luckily, the stud was not busy that afternoon. She stood fine and was bred.

After several years of working on this mare, and several embarrassing incidents at breeding sheds around Central Kentucky, we finally learned she had about a three-hour window during each cycle when she would allow a stallion to breed her.

Short cycle

A mare at another farm also was purchased at a November sale. She foaled in January, so it was too early in the year to breed her on her foal heat, but she teased normally at the appropriate time in her estrous cycle. But after her foal heat, she did not come back into heat when she should have. In fact, it was six weeks before she showed to the teaser again.

The mare was bred, and she did not come back into heat three weeks later. But she was not pregnant. She was given prostaglandin, she came into heat, and she was bred. Again she did not come into heat on schedule; again she was not in foal; again she was given prostaglandin; and she was bred again. This time she conceived.

The next year, the story was the same. But I learned something about the farm: They did not tease every mare every day. Once a mare had been bred, she was not teased again until day 16 after breeding. I also learned something about the mare: She had a two-week cycle, so she was out of heat by day 16. She would tease in heat from about day nine or day ten to day 14.

Short tease

Another pregnant broodmare was purchased at a sale, this time in January. At what should have been the appropriate time of her cycle after she had foaled, the farm began to tease her every other day, as was its custom. The mare apparently did not have a foal heat because she did not show in heat until day 28. I checked her the next day and found she had just ovulated.

We gave her prostaglandin at the proper time. She did not show to the teaser until the ninth day after the injection. I palpated her and told the manager to book her to the stallion for the following day. But on the following day, she did not tease in heat. She had ovulated.

After much time working with this mare, I found that she built a follicle and ovulated in about 12 to 14 hours, and that is when she teased in heat. Getting her booked and bred was a problem, so the farm resold her after a couple of years.

Pregnant

A client received three mares that were to board with him on a permanent basis. One was a coal-black mare of considerable size, and she had a huge, month-old foal by her side.

She teased in heat and was bred uneventfully and conceived. But 18 days after she was bred, she teased in heat again. I checked her, and she was pregnant. She teased in heat again 16 days later. I reexamined her, and she still was pregnant.

This went on for 11 months. Every 16 to 20 days, she would show in heat to the teaser.

Breed early

"The book" says to breed a mare within 24 hours of ovulation, and she will usually get in foal. A friend sent a maiden mare to me to have her bred. She did everything right up until it was time to see if she was pregnant. She was not, so she went back to the stallion.

We did this four times, and each time she had ovulated by the morning after she was bred. By July 3, it was looking as if she would go home barren, but that day she teased in heat. She had a small follicle, but it was probably four or five days away from ovulation, and the breeding shed was scheduled to close for the season the next day (July 4).

I called the stallion booking office and explained the situation. I asked if I could bring her on July 6 or 7. No, the booking secretary said, but I could bring her on July 4, which I did, figuring she would not get in foal if she were not bred. I also figured she would not get in foal anyway.

She was bred on July 4 on a little-bitty bump of a follicle. I followed her along, and she built a lovely follicle that ovulated on July 8. I called my friend and told him that he had a barren mare. But because she was still with me a month later, I decided to check her. She was pregnant.

Never in, never out

This mare I owned, so I will tell you her name: Game Squaw. She was a sweetheart, the easiest mare I ever had worked on. A twitch was never needed to do anything with her or to her. To palpate her, all I had to do was place her facing a wall or a fence so she could not walk forward. No one needed to hold her.

But old Squaw never teased--in or out. She was always the same: noncommittal. She cycled right on time, though. One day when I knew she was not in heat, I decided to jump her with the teaser to see what she would do. Nothing. Another time, when she was in foal, I jumped her with the teaser again. All she did was stand there.

Never in, always out

I imagine most people who work with mares have seen one like this: a mare that always has a headache. I have seen three of these. They always fight the teaser and resist being bred. Like Squaw, they cycle normally, but the hormonal message just does not reach the brain.

Kicker

"The book" tells us that usually a mare will not kick while she is being palpated because the veterinarian's arm in the rectum turns off the kicker impulse.

At another November sale, I was sitting with an out-of-state client while he bid on mares, mostly unsuccessfully. Finally he got one.

As I left the sales arena to go and palpate the mare, a veterinarian friend stopped me.

"Brent, was that your man who bought that mare?" he asked.

I said it was.

"Be careful," he continued. "She's the only mare I've seen in years that will kick when your arm's in her."

I thanked my friend and went out to check the mare. He was right; she fired both hind feet at me while I was palpating her.

She came to my place to board. She was not due until May, so she was pretty much forgotten, other than being fed.

She foaled on May 5. As it was getting late in the season, my client wanted to breed her on her foal heat. By this time, I had forgotten my friend's warning. My arm was in her when she fired those hind feet. Fortunately, I was standing slightly to the side, but her foot caught the leg of my coveralls, tearing it. It scared the dickens out of me.

Short gestation

"The book" says the length of a mare's gestation is about 340 days, plus or minus a few days.

Another mare that was purchased in November was one carrying her first foal. She began building a milk bag shortly after nine months of pregnancy, and my client was afraid this was a sign she was going to abort. By ten months, she had a foaling bag, and that is what she did: foal. Everything was normal, so we assumed the breeding date was wrong.

We checked the date. She had been bred only once, and the date was correct. We arranged the next mating, and she was bred--again only once--and she conceived. Ten months later, she foaled--and so forth, for several years. She never carried a foal 340 days plus a few days; it was always minus about a month.

Brent Kelley, D.V.M., is a retired veterinarian living in Paris, Kentucky.