Genetics in the Miniature Horse
Whenever you want to produce seriously, it is important to know the working principle of genetics and the consequences of certain gene crossings. In addition, almost all of the color genes existing in equines are present in the American miniature. If this great variety allows everyone to let their tastes speak for themselves, it also implies making sure to know certain anomalies or diseases which result from precise crossing. In addition, miniature horses are also affected by some genetic diseases that we are now trying to limit considerably.
Most of our horses are tested on their color gene to find out what they have and what they don't have. We will only mention here the color gene which concerns our herd and for which we take our precautions.
Silver: It is a dominant gene that is found quite often in AMHA and which acts on the pigment noir in giving him a silvery appearance. It also adds small pommelures lighter on the coat from time to time, hence its English name of "Silver Dapple". In addition to this action on the coat, the gene acts in the eyes and causes multiple congenital ocular anomalies (MCOA) of varying severity, depending on whether it is present in a heterozygous or homozygous manner. Some anomalies are identifiable thanks to a thorough ophthalmologic examination but it is still more careful not to cross two silvers horses together.
If the AMHAs are generally hardy, they remain concerned by some genetic diseases that it is good to know in order to test and act in full knowledge of the facts.
ACAN D1 to D4: These are the 4 main mutations of Dwarfism found in the American Miniature Horse. Each type having a different form and consequences on the affected subjects. Dwarfism is generally characterized by horses exhibiting hydrocephalus , deviated limbs , prognathism , deformity of the spine , abnormally small and disproportionate size. The internal organs are often damaged as well and the life expectancy of these horses is considerably reduced . This genetic disease is degenerative and affects other breeds such as the Frisian, the Shetland Pony or the Welsh. Two horses that are healthy carriers of one of its genes have a 25% risk of giving birth to an affected foal. For this reason, we have chosen to have a herd that is 100% free from these 4 genes.
Skeletal Atavism : A form of Dwarfism characterized by an imbalance in the growth of the limbs. Rarer than ACAN, it is nonetheless important to test. It is considered that 12% of the global herd (healthy and / or affected carriers) is affected by this form. There are two identified and testable mutations: Del1 and Del2 . Our two stallions, Vivo & Haston, as well as Vendetta were tested unharmed. The other mares will be tested gradually during the year 2020 and their results will be made public.
To learn more, do not hesitate to browse this article co-written by veterinary doctors Mme SACHDE and M. Leclerc for AMHA France.