Although a mere quarter of the size of your average horse, the miniature horse lacks none in the size of his personality. In fact, these little guys can act so "big", you may want to treat them just like a big horse. However, it is important to recognize that a miniature horse has some special veterinary needs that don't pertain to the big guys. Here is a short review of some special conditions that are specific to miniature horses.
Probably the most common health issue that miniature horses face is obesity. Obese miniature horses are at much higher risk for acquiring different diseases such as osteoarthritis, laminitis, and metabolic diseases. In particular, obese miniature horses can be affected by a metabolic disorder called "hyperlipemia" where the body mobilizes an excessive amount of fat in the bloodstream. Excess fat in the blood can cause fat to build up in the liver and lead to liver failure.
Because weight control can be very difficult in miniature horses, work with your veterinarian to monitor your miniature horse's weight frequently and devise a "mini-specific" nutritional plan to keep him or her at a healthy weight.
A miniature horse has the same number of teeth as the average sized horse. With their tiny dish-shaped skulls, miniature horses are prone to having teeth that are crowded, deformed, misaligned, or even rotated. These dental abnormalities without proper dental care or floating can lead to sharp spikes, infections of the tooth root, or ulceration of the cheeks and soft tissues within the mouth. For this reason, it is critical to have a complete dental examination performed early in life when the teeth are erupting (before age 2) and frequent regular exams (every 6-12 months).
The breeding process of the miniature horse can be much different than that of their large counterparts. Detection of pregnancy frequently occurs later (approximately 6 weeks after being bred versus 14-17 days) due to the fact that rectal palpation and ultrasound can be difficult to perform in such a small animal. Additionally, miniature horses have a much higher chance to experience a dystocia (or difficult delivery) than big horses. If your miniature is expected to foal soon, it is extremely important to provide excellent monitoring and to call your veterinarian immediately if trouble occurs.
All these conditions certainly make life seem bleak for our short little mini horse friends. However, there is hope! Working closely with your veterinarian for wellness examinations, nutritional counseling, and regular dental work can help prevent many of these diseases, allowing your miniature horse to thrive for many years longer than the average horse.
References: Lyons, D.J. Carey "Maximizing Mini Health" The Horse. Vol XXX, No. 7July 2013, pp. 18-22.