Pregnant mares should be vaccinated 4-6 weeks before foaling. a) Ultrasound scanning: This is by far the commonest and most preferred method of determining pregnancy. It is also a key time to make sure your mare is well vaccinated against a variety of pathogens that can affect her overall health and reproductive capacity. The foal has specialized cells in the small intestinal lining that are able to absorb the large antibody molecules present in colostrum. An inflammation of the placenta often caused by an infection invading the uterus via the cervix, placentitis is responsible for up to 40% of late-term abortions in mares. A. The spring transitional period (time to come into first heat in which ovulation occurs) is longer in thin mares than in mares in good body condition.
As well, infected foals may be prematurely born alive but soon fade and die while others are born dead at full term. Horses can be asymptomatic carriers of the disease, shedding the virus that may infect other horses without appearing clinically ill at the time. Most adult horses will have developed some immunity against the respiratory form of the disease from exposure early in life. However, exposure to the abortigenic form does not appear to be protective long term, necessitating a frequent vaccination protocol to protect against this form of the disease. Within 24-48 hours of foaling, the ligaments around the tail head and the vulva begin to sag as the mare’s body readies itself for foaling. It should also be noted that the “non-neurotropic strain of EHV-1 can also cause EHM. The colostrum is the only protection your foal has against diseases until his own immune system develops.
Ingesting colostrum in the first 12 hours post‐foaling is critical to acquiring these antibodies, as they are too large to cross the placenta while the fetus is in utero and the young foal’s gastrointestinal tract is only able to absorb them for a short period of time. These maternal antibodies provide protection until the foal is old enough to receive its primary series of vaccines and result in a stronger immune response at the time of foal vaccination than in foals from previously unvaccinated mares. DOUBLE: A Breeding Shed Form must accompany the mare each time she is presented to be bred. Now that we are in the home stretch of pregnancy, our focus shifts from the general to the specific. Abortion is defined as the situation in which the mare actually delivers a non-viable foal, somewhere between 40 and 300 days. This vaccine requires a three dose series given one month apart, beginning in the 8th month of gestation. A comprehensive health plan for your mare that includes parasite management with anthelmintics (dewormers) and booster vaccinations will set the stage for the health of your newborn foal.
Of course, vaccination only goes so far and is not a substitution for good management. “Diagnosis is made by recovery of the bacteria, which are very difficult to grow, requiring special media and a low oxygen/ high carbon dioxide environment,” Asbury states. Pregnant mares should also ideally be moved to the place where they will foal 4‐6 weeks prior to their due date in order to allow their immune systems to adjust to the pathogens present in the foaling environment. This natural exposure will also induce antibody production to these pathogens, again allowing for antibody passage to the newborn foal via colostrum. This will result in the foal being well prepared to handle the challenges of the outside world.