TDK conference 2015

The Equus Przewalski is of Asian origin and is the only existing wild horse. Once extinct but with the help of breeding management, the population seems to be increasing nowadays. Not only does the Przewalski breed differ from domestic horses by appearance but also genetically, this wild horse has 66 chromosomes.

Gastric ulcers are common in horses and according to previous studies 60% of performing horses develop equine gastric ulcer syndrome (EGUS) while this number increases to over 90% in racing horses and is much less in freely roaming horses. The chances of developing EGUS does change depending on the use of the horse and that is because of the different causative factors that range from nutrition and training to stress levels of individual animals.

The aim of this study was to evaluate prevalence of EGUS in freely roaming adult Przewalski horses.

Stomach of 11 Przewalski horses (8 males, 3 females) with the age of 2-22 years (m:9,9, sd:6) were examined postmortem for EGUS. Their body condition and general health state was evaluated by observation and reviewing their medical history. These horses spent their lives freely roaming in 2361 ha grassland biosphere reserve in the Hortobágy National Park.

We found ulcers in 3/11 (27%) horses. All affected horses were males, there were two harem stallions and a bachelor. Neither the oesophagus and the nonglandular squamous epithelial mucosa, nor the margo plicatus area did not show any alterations in any of the examined animals. The glandular part was affected with lesion number score of 2 in each case and lesion severity score was 1 in one animal, and 2 in two others. The pyloric region was always free of ulceration. None of the horses showed signs of severe weight loss.

Opposite to other horse populations, freely roaming Przewalski horses had gastric ulcerations exclusively in the glandular region. Since these horses spend approximately 50% of their time grazing, gastric pH stays more constant in the higher range making peptic injury to the squamous mucosa less likely. Most of the ulceration initiating factors described in domestic horses could be exluded based on the living style of wild horses and their medical records. Glandular mucosal erosion and ulceration can originate from stress induced impairment in mucosal blood flow and the mucus-bicarbonate barrier. Stress secondary to male dominance fights and too large harems might be the cause of glandular ulcers in wild horses. Unfortunately due to their way of living, an observational study would have been difficult to perform to see if other factors play a role in disease development or how exactly did the EGUS affect their performance or behavior in the group or alone.

The study was supported by the Przewalski Reserve of Hortobagy National Park.