Over the last century, the place of the horse in society has shifted from that of an absolute necessity, primarily used for transportation and labor, to more of a pleasure animal.
Today, horses are most commonly companion animals, lesson horses, breeding stock, and sporting competitors, with more limited use for farm and ranch work. This change in usage has resulted in an increasing geriatric horse population, and accordingly, the need to better understand the complexities of geriatric horse health.
The University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) plays an important role in its support of Kentucky’s horse industry. Between June 1, 2010, and June 30, 2012, one hundred and thirteen horses aged fifteen years and older were submitted for necropsy to UKVDL.
Review of these necropsy cases revealed that the main organ system contributing to the death of this group of aged horses was the digestive system, followed rather closely by the cardiovascular system.
Specific diagnoses of the digestive system that were noted in this group of geriatric horses included but were not limited to: strangulating lipoma; small intestinal entrapment, devitalization, and/or rupture; gastric rupture; large colon displacement, torsion, impaction and/or rupture; and necrotizing colitis of bacterial or unknown etiology.
Although prevention of these disorders is not generally possible, certain steps can be taken by own- ers to improve the digestive health of their horses. A consistent diet with sufficient roughage promotes a healthy digestive system for horses of all ages.
However, as horses age, their teeth can wear unevenly and crack or break, preventing proper mastication and hindering the digestion of food. Therefore, proper dental care is crucial for older horses, along with appropriate nutritional substitutions for horses that can no longer chew forage adequately.
Maintaining an appropriate deworming regimen for horses of all ages can also go a long way to preventing digestive dysfunction. For example, poorly-managed parasitic infections can contribute to the formation of adhesions, leading to intestinal obstruction, and tapeworm infection can lead to colic due to cecal impaction.
Once an owner notices signs of colic and digestive distress, timely veterinary intervention can sometimes improve the outcome for a horse, particularly if corrective surgery is warranted by a specific diagnosis.
Death due to disease or dysfunction of the cardiovascular system may be somewhat unexpected.
However, after delving more deeply into necropsy records, a not-so-surprising story emerged. Uterine artery rupture was responsible for approximately half of the cases where the main cause of death was attributed to the cardiovascular system. This statistic appears to be associated with the presence of numerous breeding farms in Central Kentucky.
Increased risk of uterine artery rupture is an important issue for owners and veterinarians worldwide to consider when breeding mares over fifteen years of age. Additionally, the potential high risk for uterine artery rupture in older mares may highlight the option of embryo transfers to surrogate mares to obtain offspring from highly valued aged mares.
As with any medical procedure however, embryo transfer and surrogacy are not without risk and may be restricted by certain breed registries.
While the main causes of death identified in this preliminary review for horses over the age of fifteen in Kentucky certainly highlight potential problem areas for the medical management of older horses, a more extensive review of past cases is needed to fully establish significant trends from this study.
Article courtesy of Ashton B . Miller, Graduate Research Assistant, in collaboration with Alan Loynachan, DVM, PhD and Amanda Adams, PhD. Maxwell H. Gluck Equine Research Center, University of Kentucky, Lexington, KY. Published in Equine Disease Quarterly, April 2017