June 2000

End of the Season

by LEIGH ANN HOWARD

With the breeding season essentially over for the year 2000, now is a good time to sit down and review the reproductive problems we have had during the past season.

The foal heat breedings, as mentioned last month, were not very productive, but we were able to get most of those mares pregnant on the second heat.

We had three "lactating anestrus" mares, one of whom we managed to jump-start and get pregnant. This complete shut down of the reproductive system on nursing mares, at least in our experience, seems to happen with young mares after having their first or second foals. No one knows why this happens. Sometimes injections of GnRH will stimulate the mare enough to go ahead and cycle.

Transitional mares are always a big problem. When an owner ships a mare in to be bred and the mare is showing 'in heat' at home, it is difficult for the owner to understand that the mare is not really in heat. She can be exhibiting all the external signs of estrus but not doing anything inside. We had one mare here for four months who never went 'out of heat' as far as our teaser was concerned. But her uterus and ovaries functioned normally and she is now pregnant and still teasing 'in'. The only way we were able to determine when to breed, when ovulation occurred and when she was pregnant was by palpating her regularly using the ultrasound machine. 

UTERINE CYSTS
With the help of modern ultra-sound machines we can gather useful information by taking a good look at the uterus and ovaries. Uterine cysts are one of the many issues we are able to deal with fairly successfully because of our ultra-sound machines.

Uterine cysts can be a very real problem. It is thought that the movement of the pre-implanted conceptus in the uterus somehow triggers fetal recognition by the mare. If there are many cysts and the conceptus gets lodged against one, so that it can't swim around, it is possible the mare never gets the signal that she is pregnant. Consequently she cycles again and the conceptus is lost through the open cervix.

Uterine cysts also hinder the determination of pregnancy by the veterinarian. Many cysts look just like a 15 to 20 day old conceptus. 

Two situations come up repeatedly on the breeding farm with mares that have uterine cysts:

1) If a mare has had at least two ovulations she could have twins. A mare with the possibility of twins that has uterine cysts is a real headache. A twin needs to be eliminated early if you hope to retain a single conceptus. So how do we determine what we have in that uterus? How do we know which structures are the twins and which structures are the cysts?

2) The other common case is the mare with several cysts and a single ovulation. We often can't tell whether the structures are cysts or a conceptus and the mare might feel pregnant. What if she is not coming back in heat. Do we assume she is pregnant? We could miss the next cycle making that assumption.

In both of these examples we might need to "look" at the uterus several times before a positive determination of pregnancy can be made. All cysts should be 'mapped', that is, their location and size be recorded after ovulation. This will give the veterinarian a much better idea of what he/she is looking at during the first pregnancy scan.

Owners often question the number of "re-scans" that show up on their bill. Repeated scanning becomes necessary when a correct determination of the mare's status is in question. The last thing any of us want is a mare that 
dumps twins in the fall.

In many cases we might have to wait until an embryo starts to develop in the conceptus. This is usually twenty seven to thirty days. In the center of the embryo a heartbeat should be visible.

The veterinarian can also get a pretty good idea of the health of the conceptus with use of the ultra sound machine. A conceptus with poor definition, unusual size or irregular borders should be rechecked to be sure it continues to grow and develop.

RANDOM THOUGHTS ABOUT MARES
So if we have an empty or barren mare how do we prepare for next year? 
Probably the number one aid in preparing an open or barren mare for next season is to have a Caslick procedure done. Most Thoroughbred mares eventually need this procedure done to keep them from contaminating their reproductive tract. If, in the opinion of your veterinarian, your mare may or may not need a Caslick, my advice is to have it done. It is not going to hurt and it might help.

If the mare foaled and is not being bred back she should be flushed out, given oxytocin and caslicked, if she needs it, during her foal heat. This will give her a better chance to be clean and ready for next year. Be sure to do pregnancy exams on all the mares prior to September, so stud fees can be billed and paid. And these exams should be done again in late fall. The biggest, most pregnant looking, mares can be empty in December, especially if they are on Regumate. It's pretty embarrassing to send a mare to a breeding farm to foal in April or May only to find out she is not pregnant about the time she should be making a bag. Mares bred in May and June should be checked in February. Neglecting these late pregnancy
exams will eventually cost you considerable time somewhere along the line.

FOALS
Physitis (epiphysitis) in the growing areas above the knees (below right) and ankles (below left) is very common in the two to six month old sucklings. Physitis is defined as inflammation of the growth plates of the long bones. So physitis is the result of growth. If there is too much physitis then the growth of the foal is usually determined to be too rapid. Combine the rapid growth with our hard California ground and too much exercise and you can have some serious developmental problems showing up.

Physitis in the knees.	Physitis in the ankles

Now is the time to take a good look at your suckling. Does he have bumps 
just above his ankles? Does he have ugly lumps just above his knees? Are the bumps and lumps about the same on both legs? Is the baby pretty round and plump all over? If the answer to these questions is "yes", then you need 
to make some adjustments right away. 

The number one thing you need to do is reduce the high calorie feed intake. Cut down or eliminate the grain. Add some grass hay to the alfalfa. Be sure your calcium/phosperous ratio is acceptable. Cut the high growth feeds down.
Often the lumps and bumps are hot and the foal is a bit sore. You can certainly "mud" the hot sore lumps with a cooling, drawing poultice and make him feel better. And you should limit his exercise until his body catches up with his growth rate. Placing the mare and foal in a smaller, soft, paddock for a while would be an excellent idea. 

Remember though, if the mare and foal are housed in a smaller enclosure for any length of time, to be sure to release them gradually back into the herd. Trauma induced OCD lesions are thought to occur when a cooped up baby is suddenly turned out in a large pasture and overextends unused muscles and ligaments.

VACCINATIONS
We have been bombarded with new research and material about vaccination schedules for the past year or so. We have been told that we might as well be squirting our Flu/Rhino vaccine into the dirt instead of giving it to our foals before they are 9 or 10 months old. If the mare has been vaccinated within the last trimester of her pregnancy with Flu/Rhino, the foal should be covered under a 'maternal antibody influence' until some time after the nursing has stopped. 
This sure goes against what most of us have been doing for more years than I can count. Maybe this is also true of the other vaccines we routinely give our sucklings. I guess we won't know until more research is done.

I have noticed for years that I get far fewer coughs and respiratory tract infections in my young horses in training at San Luis Rey Downs than most trainers. This is probably because I vaccinate with Flu/Rhino about 30 days before the yearlings go in and then give them a booster thirty days later. So, from the recent research it looks like my yearlings main protection is coming from these vaccinations, not the ones I did back when they were sucklings.

Another point the researchers have stressed is that the longer you can wait before doing the series of the Tetanus Toxoid and Encephalomyelitis (Sleeping Sickness) vaccinations, the more effective they will all be. The consensus is if you can manage to keep your herd healthy until they are four months old your vaccination program will be much more effective.

You might want to go back and read 'Ask The Vets', based on Dr. David Wilson's presentation at the 14th annual Horseman's Day seminar at Davis, in the California Thoroughbred July 1999 issue.

QUIZ
Questions: Are there twins? Where is the conceptus? Which mare is pregnant?
Answers here.

Answer: No pregnancies exist, all ultra-sound objects are cysts.

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