Written by: Sallie S. Hyman, VMD, DACVIM, CVA
They might fit into the back of the Suburban or even hang out in the living room, but Miniature Horses need to cared for like any other horse. Minis have the same health needs and risks as other breeds, as well as a number of more unique issues. Here are 12 medical conditions common in Miniature Horses.
1. Angular limb deformities. These are deviations from a limb's normal axis as viewed from the front or behind. Minis are often born with (in other words, it's congenital) severely crooked legs, which can cause difficulty walking, abnormal hoof wear and discomfort. Surgery can correct some deformities.
2. Upward fixation of the patella. With this condition, the patella (kneecap), which is part of the stifle joint, gets hung up on the femur's medial trochlea (a protrusion on the inner part, above the patella) and "locks" the stifle in extension - basically, this looks like a stiff, outstretched leg. Usually, the horse can eventually "unlock" the patella by backing up. In some extreme cases, both hind limbs are affected and the Mini stands parked out and unable to move forward. Treatment includes blistering, splitting or cutting the medial patellar ligament that connects the kneecap to the tibia below.
3. Luxated patella. This can cause a similar stance as upward fixation of the patella and might result in long-term lameness. The patella luxates (Dislocates) laterally, or to either side, due to congenital abnormalities of the stifle region, including a shallower than normal femoral groove (where the patella slides) and a hypoplastic (abnormally small) or deviated tibial crest, which is the front edge of the tibia. Veterinarians must reposition the tibial crest and deepen the femoral groove surgically.
4. Malerupted teeth. Minis commonly retain their deciduous (baby) teeth, impeding eruption of the permanent teeth and causing overcrowding. Often, the deciduous teeth must be pulled.
5. Overbite/Underbite. Jaw deformities are common and serious. In the brachygnathism, or parrot mouth, the upper incisors hang over the lower ones. In prognathism, or monkey mouth, the lower incisors extend beyond the upper. Both require frequent dental care. Severe cases can prevent Minis from chewing food properly.
6. Sinusitis. The roots of the molars are located in the sinuses of the skull. With overcrowding of the teeth comes overcrowding of the roots in the sinuses. This can prevent normal sinus drainage and allow trapped bacteria to multiply, causing a sinus infection.
7. Fecaliths and enteroliths. Fecaliths are rocklike manure impactions caused by poor mastication (chewing) of food, poor-quality feed, or eating foreign materials. Enteroliths are rocklike masses that occur when minerals form around some nidus, such as a swallowed rock or other foreign material. Fecaliths commonly develop in the small colon, whereas enteroliths can occur anywhere in the gastrointestinal tract. Occasionally, they will pass with fluids and mineral oil, but most cases require surgical removal.
8. Hyperlipidemia/Hepatic lipidosis. Minis store fat easily. If they go off feed or are stressed due to pregnancy, lactation or disease, their bodies begin to mobilize fat into the bloodstream and then to the liver to process into energy. This fat accumulation can cause liver swelling and reduced liver function, failure and death. Any Mini that is off feed for 24 hours is at risk. Signs include anorexia, fever, colic, diarrhea, jaundice, head-pressing and circling. The mortality rate is 60-100%, so swift intervention and treatment is key.
9. Obesity. Minis have evolved to be very efficient at utilizing minimal amounts of calories. Most do not require grain, yet overfeeding is common. Offer hay at 1.5-2% of each horse's body weight per day, minimize grazing and use muzzles as necessary.
10. Dystocia. Due to discrepancy between Mini mare pelvic size and fetal head size, dystocia (difficult birth) is common. Veterinarians often perform a cesarean section.
11. Dwarfism. The two most common types of this genetic condition are achondroplasia (short limbs) and diastrophia (twisted limbs). Achondroplastic dwarfs usually get around well and live normal lives. Diastrophic dwarfs have multiple limb deformities, domed heads and roached backs, and they generally need support, including splints or surgery, to move properly.
12. Anterior segment dysgenesis (ASD). In this condition, certain parts of the eye, such as the cornea, iris, lens, ciliary body and retina, do not develop normally. One of the most common and apparent abnormalities is an enlarged cornea that gives the eyes a "bugged-out" look. Horses with ASD are at increased risk for vision loss.
Owning Miniature Horses can be a fun venture as long as you are armed with the information you need to be prepared for and care for their special needs.
Article provided courtesy of AAEP-Media Partner, The Horse.