Esophageal Dysfunction in Friesian Horses: Morphological Features.

The research investigates the morphological changes in the esophagus of Friesian horses that have megaesophagus, a condition which appears to be more prevalent in this breed. The findings suggest that megaesophagus in Friesian horses may be hereditary.

Introduction

• The research focuses on Friesian horses, a breed that has a higher prevalence of megaesophagus, a condition characterized by the dilation and often poor motility of the esophagus.
• The study was carried out at the Wolvega Equine Clinic and the Utrecht University Equine Clinic. The research recorded that around 2% of Friesian horses presented to the clinics had megaesophagus.
• The research sought to compare the morphological changes in the esophagi of Friesian horses with megaesophagus to those of six healthy control horses.

Methods and Observation

• Of the 18 Friesian horses with clinically observed megaesophagus, only 12 of them displayed esophageal dilation during necropsy. The dilation generally occurred in the thoracic portion of the esophagus.
• Hypertrophy or abnormal enlargement of the lower or distal esophagus was only observed in one third of the affected horses. This indicated that muscular hypertrophy did not play a significant role in causing megaesophagus in Friesian horses.
• The researchers observed increased deposition of clumped and disorganized collagen in the non-dilated portion of the esophagus in the clinically affected horses.
• On necropsy, there was a decrease in neural elements and elastin, mainly found in horses with megaesophagus.
• It was also found that degeneration and necrosis of the tunica muscularis, the muscle layer of the esophagus, were present alongside the entire esophagus in clinically affected horses whereas it was rarely found in control animals.

Findings

• The findings from the study showed no significant differences between affected and control horses with respect to inflammation, mineralization, and the number of cells of Cajal, which are the cells involved in the contraction of muscles in the gastrointestinal tract.
• The researchers found that the higher prevalence of megaesophagus in Friesian horses compared to other breeds and the presence of abnormal collagen in very young Friesian foals supported the hypothesis that megaesophagus in Friesians might be hereditary.
• The study concludes by proposing a possible hereditary component to the prevalence of megaesophagus within the Friesian breed.