Wednesday, 15 September 2010 08:17


Written by  A.J. Neumann, D.V.M
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When that question is put to me the only way I can possibly answer it is to refer back to the many phone calls I have received from people who have a problem with the pregnant mare and they are seeking help.

This past foaling season I received many calls asking for advice in dealing with one or two conditions which can occur in the pregnant mare. These are health problems which seem to have been fairly common in the past foaling season.

They are, in order of their frequency; ventral edema, occurring on the lower abdomen and chest of the pregnant mare, and mastitis which can occur in the udder prior to or after foaling.

The individual who calls about one or both of these problems wants to know the cause, treatment and prevention of them.

Let’s talk first about the pregnant mare with the abdominal-thoracic ventral edema. According to the phone calls I receive on the subject, the number of cases could be on the rise or a new generation of draft horse breeders have never seen it occur in their stock. I suspect both factors are at work here.

The ventral edema of the abdomen-thorax area will occur in some pregnant mares in the last trimester of their pregnancy. The first indication of fluid retention will usually occur just ahead of the udder. As the days and weeks pass the edema will worsen and move forward on the bottom of the belly. It will eventually involve the whole area of the ventral portion of the abdomen and spread into the underlying tissues of the ventral chest area. In the extreme worst cases, the rear and front legs will become swollen and edematous. The edematous area on the underside of the belly will be three to four inches thick and as wide as the whole abdomen.

A person can place his or her hand on the swelling and by applying pressure with their fingers easily “dent” the area. These dents will remain in place for several minutes. This simple test will prove the area swelling is edematous and the tissue is filled with lymphatic fluid.

As the edematous area continues to expand, the mare will continue to eat well and appear normal with no evidence of a temperature rise. If the mare’s legs should stock up she often will not move too far from food or water. These same mares will be reluctant to lie down and spend all of their time on their feet.

When diagnosing this condition, especially in its early stage when the swelling first occurs just ahead of the udder, the party checking the mare must examine the udder and be sure it is healthy and not showing any evidence of mastitis.

Another condition which must be ruled out is the presence of a wound in the area. Even one as small as a puncture could cause an infection to occur in these tissues. Of course, if this were to be the case, the mare would be carrying a higher than normal temperature and her appetite would soon be affected.

Purpura Hemorragica is an auto-immune disease of the horse which could be confused with ventral edema in the pregnant mare. This condition, when present, will cause edema on the underline of the thorax and abdomen. In most cases all four legs will be swollen as well as the neck and head of the animal. Purpura Hemorragica has to be ruled out in the diagnostic process.

The cause of the ventral edema is simply the fact that the pregnancy has interfered with the return of venous blood from the ventral area of the mare which includes the abdominal area, thorax and legs.

This condition almost always occurs in the mare who is being very well fed and who is confined to
a relative small area with little or no exercise.

The treatment of these cases is symptomatic. First, cut down on the feed. Usually these mares are being overfed especially with grain. The most important therapy is to exercise the animal. Actually a heavy pregnant mare can be used for light work around the farm right up to foaling. Do not push them when working them or ask them to back a heavy load in difficult surroundings. If one does not have work for this mare just hitch her and drive her around as she needs exercise.

The ventral edema condition can be prevented by providing exercise for the mares and by not overfeeding them. Pregnant mares, which are not being worked, should not be confined to a small yard. Instead they should have their hay fed, during the day, out in some field where they have to walk out to get it. Any exercise place that can be adopted for them is the best for their health.

If your mare has ventral edema do not give her a diuretic drug. This is a drug which causes the animal to urinate and remove fluid from the body. Do not use this class of drugs on these pregnant mares!

A mare suffering from mastitis is very different from the mare with ventral edema.

Upon examination one or both sides of her udder will be swollen, warm to the touch, and the contents of the udder will not resemble milk. It may be “stringy” or have the consistency of “curds” or be “pasty”. It may be brown colored to bloody.

As a rule the mare is “sick” in that she is off feed and has a high body temperature. A mare suffering with mastitis often will not let an individual touch the udder because it becomes swollen and very painful. If she is nursing a foal the foal may not be able to nurse if one-half of the udder is good. The mare simply does not want the udder touched.

The diagnosis of mastitis in the mare is easy but the treatment of it is sometimes difficult. The affected udder must be “milked out” at least twice a day, if possible. Usually the mare must be restrained, in some fashion, to accomplish this. If she is nursing a foal the job will often be much simpler. If she is not nursing and the udder is painful and sore to the touch the individual horseman will have his or her work cut out
for them.

The mare with mastitis must be treated with adequate doses of antibiotics. The best results are obtained by giving some of these by the intravenous route as well as administering others intramuscularly.

I treat some of the difficult cases by giving them oral antibiotics for 30 days after they have had their initial IV and IM course of antibiotics. This program works very well for mares with difficult cases of mastitis.

Pregnant draft mares have many other health problems which their owners have to confront and deal with. However the ventral abdominal thoracic edema and mastitis entities are the two conditions where by owners seek advice from me. As a result I have to rank these two as the most common health problems of the pregnant draft mare.

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