Veterinary school lessons sometimes are disproved in the real worldSeveral years ago I was called to care for a mare in the midst of a particularly difficult delivery. The mare, in her late teens, was particularly valuable-she had produced three stakes winners, one graded-and the foal she was unsuccessfully attempting to deliver was the result of a $30,000 stud fee.

When I arrived, I found the mare flat on her side with the foal's head and one leg protruding from her vulva. Contractions had ceased, the foaling man told me, and, "She's just layin' there like she's dead."

She was not dead, though. There was the occasional respiration and the eye away from the stall floor blinked once, but those were her only signs of life.

Trying to get the foal out was the main concern, and he was gettable. The right foreleg was bent at the knee and, although it required a little time and manipulation, he was brought into the world not too much the worse for his ordeal.

But the mare just laid there. She had offered no resistance to my manipulations of her foal and responded not at all to the feeble nickerings of the baby. I turned my attention to her. While I was listening to her heart, she wretched once and extended her head. Then a foul-smelling efflux oozed forth from her mouth and she stopped moving.

"Darn," I said, "she's dying." That is one of the things we learned in veterinary school: Horses do not-cannot-vomit.

They have a band of smooth muscle around the esophagus as it enters the stomach, and peristalsis cannot run backward through smooth muscle; once food enters the stomach, it can only exit through the small intestine. If it goes the other way-back through the esophagus-the horse is dead or nearly so. Or so we learned in school, and so the books tell us.

But then the old girl rolled up on her sternum and called to her foal. In another minute she stood up, shook herself, and began nuzzling the foal.

"When's she gonna die?" asked the foaling man.

I was right. She did die-six years and four foals later, when she was well into her 20s.

As I said, we learned that horses cannot vomit. Maybe this is the only one who can, but she negates all that we were taught.



Hydrops

We also were taught that hydrops associated with pregnancy does not occur in horses. Hydrops is an excessive accumulation of fluid, in this case amniotic or placental hydrops. One textbook said it succinctly: "Hydrops does not occur in horses." That is pretty clear.

My first breeding season out of college, a client asked me to look at a mare who was getting very big but was not due for several months. I looked at her, and he was right. She was huge. On rectal palpation, all I could feel was a gigantic water balloon.

I thought it was hydrops, but I was afraid to say so. I told my employer, a veterinarian of some 20 years' experience. He checked the mare and agreed with me, but said, "I've always believed that hydrops doesn't occur in horses."

Several weeks later, I was called when the mare went into labor prematurely. I got there in time to see her water break. I do not know how much fluid came out-it had to be 50 gallons or more-and the accompanying ten-month fetus was small, gasping, and malformed. It died within minutes.

Since then I have seen two more hydrops cases and read of several others. It does occur in horses.



Dirty maidens

In school, we were told there was no need to culture maiden mares before breeding them. "Maiden mares can't be dirty," we were told. When I left school, cultures on maidens were not required by stallion management.

On routine examination of maidens, however, veterinarians noticed that not all appeared normal, that there were signs of inflammation in some. Many of my clients would not allow them to be cultured, but the occasional culture was taken, and some came back dirty.

Of course, this is easily explained in retrospect. It is usually a function of suturing during their racing careers. Some who should have been sutured were not, allowing contamination to enter. And some were sutured too far down, creating a backflush of urine that entered the uterus through the cervix when that structure was open. In either case, mares who never had a foreign object inserted vaginally nonetheless had uterine infections.

Now, to the best of my knowledge, all breeding sheds require cultures on maidens.

I am not suggesting by this that we will soon learn that all horses vomit regularly and live to tell of it; what I am saying is that "never" is a long time and we should never, or hardly ever, rule out an occurrence just because no one has ever reported it.