PREGNANCY MAINTENANCE - EQUINE INFO - EQUIVET AUSTRAILA

Maintenance of pregnancy means prevention of pregnancy loss by abortion or resorption (EED). Success will depend on many factors including condition of the mare, age, stress levels and conformation of the pelvis and vulva. Unfortunately the incidence of abortion is always highest in those mares which are most difficult to get in foal in the first place. No single regime is ever totally effective and the regime of choice will depend on the stage of pregnancy and the value of the foetus.

1. Although more and more evidence suggests that a deficiency in progesterone production by the mare is not a significant cause of pregnancy loss; many mares are treated with natural and synthetic progestogens. P4 is the maternal hormone which maintains early pregnancy and is produced by the ovaries until 100-150 days. The placental unit starts secreting progestens (P4 like hormones) from around 60 days but are only capable of maintaining pregnancy solely after day 80. There are several types of progesterone supplements:-
   • Regumate
     Regumate (Equine 12cc or Porcine 6cc) daily is always the treatment of choice for maintenance of pregnancy. Mares can be started any time from the time of ovulation and maintained until full term. Cost is approximately $5.00 per day. Some may choose to treat only from the time of first pregnancy diagnosis until the placenta takes over production of progesterone (120 days). Alternatively it may be used close to term when faced with threatened abortion ie: running milk. This is the only form of progesterone supplement which has been proved to be effective.
   • Depoluteine
     Depoluteine is a long acting injectable form of progesterone and can be given once weekly throughout the pregnancy. It has not been shown conclusively to be effective but does have a good steroidal effect ie; the mares do well.
   • Progesterone Injections
     Straight Progesterone may be injected on a daily basis. Again effectiveness is inconclusive. Normally this therapy is only used in cases of threatened abortion and is not as effective as regumate.
   • Progesterone Implants
     Implants supposedly slowly release progesterone from a pellet placed in the neck. The amount of progesterone released is very low and is not considered sufficient to be significant. Some broodmare owners are, however, convinced of its efficiency. Implants last approximately 90 days and should be given at 3 months, 6 months and 9 months.
   • Cue-mates, PRIDS or CIDR'S
     These are slow-release progesterone devices which can be placed in the vagina and help to maintain progesterone levels during the early stages of pregnancy. They are cheaper and more convenient than regumate. They do cause a transient vaginitis.
2. Antibiotics
   Although lacking scientific data, many older problem mares will respond to periodic treatment with antibiotics throughout the pregnancy. Treatments vary from long acting Penicillin on the first day of each month of the pregnancy to Neopen or Trimidine for the first three to five days of each month. Evidence suggests that Trimidine achieves the highest antibiotic levels inside the uterus.
3. Maintance of good condition, good pasture (no Penny Royal), low stress and the use of rugs to prevent cold stress will always be useful. Separation of pregnant mares and young horses/competition horses will reduce incidence of Herpes Virus (EHV I & IV) as will regular vaccinations against EHV I & IV. Regular vaccinations cannot be relied on alone. Mares should be vaccinated at 5, 7 and 9 months. Also avoidance of access to progressionary caterpillars may be a factor.

My advice to owners of bad breeding mares is to use regumate until 120 days and then start on the monthly antibiotics therapy at 60 days. If the mare threatens to abort at any stage during the pregnancy (ie: makes up milk or develops a discharge) consult your Veterinarian and start antibiotics and regumate immediately.