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MINIATURE HORSES

PREGNANCY & FOALING

ABORTION & PROBLEMS OF BIRTHING
BASIC HEALTHCARE MAINTENANCE IN MINI’S

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ABORTION & PROBLEMS OF BIRTHING

Although the majority of pregnancies are without complication, miniature mares do seem to have more problems with certain aspects of pregnancy. Horses experience the majority of pregnancy losses before day 40, mini’s lose their foals more frequently after the 40th day of pregnancy. Not many studies have been done on the subject, but one report showed a range for abortion between day 120-215 which as mentioned is not the time most foals are lost in mares.
Dystocia or difficult delivery, as might be expected, is much more common in mini’s than horses. Miniature horses have genes for large foals and occasionally dystocia occurs because a foal is too large for its mare. Although size mismatch is a common cause of dystocia in dogs, it is extremely rare in the mare. Often after a dystocia, miniature mares revert to the non cycling segment of their reproductive cycle and are commonly referred to as “anestrus”. Anestrus mares cannot become pregnant; perhaps this is a safety mechanism in the mini to effectively induce reproductive rest after a traumatic incident. Another possible consequence of dystocia in mini’s is a higher incidence of uterine and vaginal adhesions. These adhesions or scars are often the direct result of dystocia and serve to increase the potential for dystocias in the future because they often decrease the size of the birth canal.

Another complication of pregnancy in mini’s seems to be the increased incidence of premature placental separation and failure to “break water”. The placenta is the connection between the mares uterus and the fetus. It is responsible for supplying the fetus with nutrients and oxygen. During the birth process a foal usually doesn’t try to breathe until they are fully delivered. If the placenta is attached properly regardless of whether the foal breathes or not it is still getting oxygen from the placenta. The consequences of premature placental separation is that the foal is deprived of oxygen and can suffer brain damage in a very short time. The failure to break water is actually the placenta not opening at the proper time to allow delivery of the foal. The effects on the foal are unfortunately similar to premature separation.

Congenital Abnormalities: Type A vs. type B
Although many of the problems described above are more common in minis than horses type A miniatures are more prone to many of these abnormalities than type B. Miniatures are classified into 2 categories according to size; type A are less than 34 inches and type B are 34 - 38 inches tall. Type A mares fail to break water more frequently and have more embryonic losses. Type A 2 and 3 year olds also have lower conception rates. Lower conception rates mean that the mare must be bred more times during the breeding season to achieve a pregnancy. Type A mares also have more dystocia and foals with congenital problems (abnormalities developed during the pregnancy) like dwarfism and jaw malalignment. Dwarf foals are minis which look like dwarfs rather than miniature horses. They may have one or all of the following: domed head, short leg to body, short stubby necks and large heads. Some foals grow out of these abnormalities as they mature.

Another abnormality observed in many miniature foals are flexural limb deformities in two or more legs. Flexural limb deformities are abnormal contractions of the tendons in the front legs which result in the foal not being able to straighten its legs. Frequently, exercise and corrective shoeing and trimming eliminates the problem. The kneecap is also an area of particular weakness in minis as is the eye; problems in these parts of the mini are all too common.

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