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Minature medicine poses big distinctions
Miniature horses require heightened level of care, more reproductive concern


DVM360 MAGAZINE


Reproduction and vaccinations


This normal foal and normal herd are the result of diligent veterinary care and conscientious owners. Veterinarians should see miniature patients twice a year.
Another interesting variation in miniatures involves the descent of testicles in stallions. Most full-size horses are considered cryptorchid or "retained" if the testicles have not dropped or descended into the scrotum after the first year. Dr. J.E. Cox PhD, chairman of Equine Studies at the University of Liverpool (England) has described a condition termed Temporary Inguinal Retention that is observed in small ponies and miniatures. This condition is characterized by small testis that can grow and ultimately descend into the scrotum by the time the animal is 3 years old. This parallels the experiences of many mini breeders who have seen similar situations among their horses. Veterinarians should be aware of this possible variation in miniatures so they can advise their clients accordingly.

Vaccination recommendations are comparable to those for FSH. Dr. Elizabeth Metcalf, a theriogenologist in Sherwood, Ore., who has extensive experience with miniatures, cautions: "Be sure to use the full equine dose of vaccines, especially for killed Rhinopneumonitis in pregnant miniatures since there have been recorded abortion problems when a reduced dosage was attempted."

Metcalf also mentioned a few of the many differences seen in mini reproduction and some of the problem areas as well.

"The sperm of miniature horses is actually smaller than that of FSH," Metcalf says. "But there is no real difference in follicular size and development toward ovulation between mini mares and fullsized mares."




Reproduction is, in fact, the area where mini owners are most likely to need veterinary assistance. Metcalf reports a late-term abortion rate of almost 25 percent, in her clinical experience, compared to 12 percent for FSH.

"This increased abortion rate is largely due to a maternal/fetal mismatch or imbalance since the mare is often carrying a fetus that is disproportionally larger than her uterus," Metcalf explains.

There is simply not enough room, and a placentitis and resulting abortion often occur.

Those miniature mares that do go to full term frequently require veterinary assistance at delivery. The general rule is to breed a larger mare to a smaller stallion, but the quest for smaller and smaller foals can result in many problem deliveries. Veterinarians should strongly advise their clients to be sure that their mare's foaling is definitely observed, and oftentimes, it is advisable to have the mare at a location where assistance can be given quickly if needed.

Foaling detection devices are very useful for miniature clients and can be the difference in a live or dead foal. Because foaling is such a risky and important time for miniatures, it becomes crucial to have accurate breeding dates. Unfortunately many minis are bred naturally at pasture, and many veterinarians are understandably reluctant to perform ultrasound examinations to ascertain exact pregnancy dates. Additionally, the lack of routine ultrasound examination results in many missed reproductive problems, such as persistent Corpora Luteum, uterine infections, cysts and any number of other conditions that currently are handled routinely in FSH through the use of ultrasound.

An article in Equine Practice in May, 1992 explained the use of an ultrasound probe sleeve made from a plastic bovine pill gun. This sleeve can be adapted to fit most ultrasound probes, and it can then be used to introduce only the ultrasound probe rectally into the smallest of miniatures. Some practice is required, but this technique will allow clinicians to perform ultrasound examinations on miniatures to determine ovulation, pregnancy and all of the other information currently available to practitioners working with FSH. Once exact breeding dates are established, it becomes easier to anticipate delivery, and fewer lost foals may result.

Abnormalities

Even with the best of management, difficult deliveries can result largely because of the potential for dwarfism characteristics in miniatures. In an article in the American Miniature Horse magazine, Barbara Ashly writes: "Any breed of animal that attempts to reduce size has to accept dwarfism as an unwanted byproduct."


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Source: DVM360 MAGAZINE,
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