Cushing’s May Affect Digestion in Horses

In healthy horses, absorption of many nutrients takes place in the small intestine. The lining of the small intestine is covered with countless villi, tiny finger-like tissue projections that greatly increase surface area and allow blood vessels to absorb nutrients and carry them throughout the body. The lining also contains crypts, glands that secrete digestive enzymes and aid in nutrient absorption.

Horses with pituitary pars intermedia dysfunction (PPID), an endocrine disease that affects many older equines, often lose weight. Weight loss, poor nutrient absorption, and malnutrition in humans and some other animals have been tied to reduced integrity of the small intestine tissues.

Research at Michigan State University was designed to test the hypothesis that a similar loss of condition in horses with PPID might be related to changes in the small intestinal villi and crypts that could prevent nutrients from being absorbed. Conclusions from the research were presented at the 7th European Workshop on Equine Nutrition held in Leipzig, Germany.

To compare tissue characteristics in the small intestines of PPID horses and normal horses, the researchers used a group of 15 horses, 11 with PPID and 4 healthy horses. The mares and geldings were 25 years of age or older and were of several breeds. They were fed hay and senior feed for five days after which they underwent an overnight dexamethasone suppression test to confirm the diagnosis and severity of PPID. They were then euthanized and tissue samples from three locations in each horse’s small intestine were gathered.

Examination of the tissue samples showed crypt changes and shorter villi in the PPID horses compared to horses that did not have the disease. These changes indicated differences in nutrient digestion that had the potential to reduce absorption capacity in animals with PPID. The researchers concluded that continued work will be necessary in order to develop alternative nutritional strategies and medications to manage horses with PPID.

Kathleen Crandell, Ph.D., an equine nutritionist at Kentucky Equine Research (KER), suggested that when horses absorb only a limited percentage of ingested nutrients, it is sometimes helpful to increase the intake level of these nutrients so that a larger amount is available for use. Micro-Max is a low-calorie, low-starch source of vitamins and trace minerals. It supports optimal digestibility through the inclusion of yeast culture and is suitable for use in both horses and ponies. Horse owners in Australia can use a similar product, Gold Pellet. Both nutritional supplements are produced by KER.