Bettina Dunkel, Senior Lecturer in Equine Medicine

In relation to health, differences between ponies and horses have long been recognised, particularly regarding metabolic and endocrine responses. It is well established that ponies, in comparison to horses, are more insulin resistant and have higher blood glucose levels.

In addition, ponies and miniature breeds are much more prone to development of hyperlipaemia secondary to disease and a negative energy balance. Many clinicians also feel that treatment of hyperlipaemia in ponies and miniature breeds is more difficult compared to horses, with animals not infrequently succumbing to the condition.

Other dissimilarities between breeds have received comparably less attention. Recently, lactate and glucose concentrations in horses and ponies with gastrointestinal disease were investigated in two large studies based at the RVC including 384 horses and 161 ponies. Results of the first study have been published in the Equine Veterinary Journal and findings of the second study are about to be published the Journal of Veterinary Emergency and Critical Care.

Both studies showed that ponies had significantly higher lactate and glucose concentrations compared to horses with gastrointestinal disease. This discrepancy persisted when the nature of the colic lesions was accounted for and was apparent for a variety of different conditions. Statistical analyses demonstrated that being a pony was one of the main factors influencing lactate concentrations.
Interestingly, lactate concentrations in healthy ponies and horses were similar, refuting the theory that higher baseline concentrations in ponies were responsible for the observed changes. Reasons for these findings are still unknown but differences in ponies’ responses to stress, pain or hypovolaemia have been postulated.

The findings are clinically highly relevant as plasma lactate concentrations remain an important parameter in the assessment of equine colic cases. In particular, high lactate concentrations are used as a marker for the need for colic surgery. Knowledge of these breed predispositions can help clinicians when assessing clinical cases and can avoid misinterpretation of test results.

Ponies not only respond differently to gastrointestinal disease, they also vary in the development of colic lesions. Colon displacements and colon volvuli are rare in ponies. This has been anecdotally reported for a long time but was recently substantiated in an investigation involving close to 600 horses and ponies.

The study found ponies and miniature types were 90% less likely to develop any type of colon displacements compared to light breed types (predominately warmbloods and thoroughbreds), with even smaller chances of developing a left dorsal displacement (LDD). Development of LDD has previously been associated with height, with tall animals being predisposed to encountering this type of lesion. In the study, all animals with large colon displacements were ≥ 142cm and all animals with a colon volvulus were ≥ 145cm.

Several studies have identified an increased risk for strangulating lipomas in ponies and also in Arabian horses. Additional factors include age, with an increasing occurrence in older animals suggesting that lipomas gradually increase in size and/or number over the lifespan of equids. Interestingly, strangulating lipomas seem to be rare in miniature breeds, with only very few cases reported in the literature.
Ponies also had increased chances of developing non-strangulating small intestinal lesions other than enteritis. This was an unexpected finding, particularly as the lesions in ponies were predominately intraluminal obstructions of duodenum, jejunum and ileum, which is traditionally considered a relatively rare finding in horses.At RVC Equine we are well-equipped to handle all types of colic cases in horses and ponies. Due to our active research interest in colic and all other intestinal diseases, particularly colic in ponies, we are able to incorporate the newest research findings in our assessment and treatment. Our state-of-the-art facilities include ultrasonography, endoscopy, CCTV monitored stables, in-house laboratories and dedicated operating theatre. And, last but not least, our dedicated and highly experienced team is onsite 24 hours a day, seven days a week, to provide the highest level of care for our patients.

To discuss a case or make a referral call us on 01707 666667 or email equinehospital@rvc.ac.uk.