Yearling laryngeal function grades II.2 and below are not associated with reduced performance.

The research examines whether the function of a Thoroughbred yearling’s larynx – graded as Yearling Laryngeal Function (YLF) – impacts its future racing performance. The study shows that 95% of the yearling population had either I, II.1 or II.2 YLF grades and little disparity was noted in their race outputs. However, horses with a III.1 YLF grade performed well in the early stages of their career but underperformed as they aged four years or more.

Objective

• The purpose of the study was to ascertain if there’s a correlation between the YLF grade of Thoroughbreds and their future performance in races.

Methodology

• The researchers carried out a retrospective cohort study.
• They reviewed endoscopic recordings of horses after sales from Australian yearling races in 2018 and 2019.
• The race performance of these horses was evaluated throughout their career and at different ages — as 2-year-olds, 3-year-olds, and 4-year-olds or older.
• A multivariable generalized linear model was used to investigate the association between YLF grades and performance. The risk estimates were presented as coefficients with a 95% confidence interval.

Results

• Out of the 5175 examinations conducted, distribution of YLF grades were as follows: I (29.8%), II.1 (49.0%), II.2 (16.5%), III.1 (3.9%), III.2 (0.8%) and III.3 (less than 0.04%).
• Other observed endoscopic abnormalities included ventroaxial luxation of the corniculate process, arytenoid mucosal lesions, and intermittent dorsal displacement of the soft palate.
• Differences in career earnings were noted based on the YLF grades. However, there was no significant difference in earnings for YLF grades II.2 and III.1 when compared with reference grade I/II.1. Horses with grade III.2 earned noticeably less overall.
• Earnings of horses age four years or older were less for grades III.1 and III.2.

Conclusions

• The retrospective study lacked follow-up data. Additionally, horses that had not raced and those with no prize money were excluded from the analysis.
• Despite these limitations, the study concluded that 95% of the yearling population possessed either I, II.1 or II.2 YLF grades and there was negligible disparity in their race performance.
• Horses with a III.1 YLF grade demonstrated equivalent performance to grades I/II.1 in their early careers, but their performance declined when they were four years or older.