Cohort study examining long-term respiratory health, career duration and racing performance in racehorses that undergo left-sided prosthetic laryngoplasty and ventriculocordectomy surgery for treatment of left-sided laryngeal hemiplegia.

This research study explores the long-term respiratory health, racing performance, and career length of racehorses that have had left-sided prosthetic laryngoplasty and ventriculocordectomy surgery for left-sided laryngeal hemiplegia, revealing that these horses are at increased risk of respiratory issues, which can potentially shorten their racing careers.

Study Overview

The main focus of this study was to investigate the impact of prosthetic laryngoplasty with ventriculocordectomy (PLVC) surgery on long-term respiratory health, the duration of a racing career, the number of starts, and the number of starts earning stakes money. This surgery is often performed on racehorses to treat a medical condition known as left-sided laryngeal hemiplegia (LLH). The study adopted a retrospective cohort design, drawing data from the record of Thoroughbred racehorses from the time of importation to retirement.

Methods

• The racehorses that had undergone PLVC for LLH and met certain inclusion criteria made up the surgical cohort that the researchers examined.
• The researchers matched each surgical case to two unexposed racehorses according to their trainer, year of import into Hong Kong, and pre-import international handicap rating.

Findings

• The results showed that the surgical cohort had a significantly higher incidence of respiratory disorders such as excessive tracheal mucus and severe exercise-induced pulmonary haemorrhage (EIPH) compared to the unexposed matched cohort.
• Racehorses in the surgical cohort had significantly shorter racing careers primarily due to retirement caused by EIPH.
• The surgical cohort had fewer race starts after surgery/matching, but the number of starts for which they earned stakes money was not significantly different from those in the unexposed cohort.

Conclusions

• Based on the study’s findings, the researchers concluded that racehorses with LLH that are subjected to PLVC surgery are at an increased risk of developing severe respiratory disorders (IAD and EIPH).
• This increased risk can potentially reduce a racehorse’s career compared to those with normal laryngeal function.
• For performance in terms of race starts, racehorses that had undergone PLVC surgery had fewer starts, but this did not affect the number of starts for which stakes money was earned, which was similar among those in the unexposed cohort.
• Therefore, owners and trainers should be aware of these risks and understand that the surgical intervention for LLH may potentially affect respiratory health and shorten the horse’s racing career.