SummaryReasons for performing study: P roximal sesamoiditis has been a common and confusing radiographic diagnosis in T h o ro u g h b red yearling surveys. This study categorised the radiographic appearance of yearling proximal sesamoid bones and determined their e ffect on the number of races s t a rted and earning potential for racing at ages 2 and 3 years. as 2-year-olds. T h ree or m o re enlarged vascular c a n a l s a ffected horses at ages 2 and 3 years, which should be taken into account when examining radiographs for p o t e n t i a l p u rchase of young horses.

Although PRP-treated horses were more likely to start a race during the 2-year-old racing year versus control group horses, results for horses in each group were not significantly different for the 3- and 4-year-old racing years. Therefore, the PRP treatment protocol evaluated in this study did not seem to improve future racing performance of yearling Thoroughbreds with proximal sesamoid bone inflammation and associated SLB desmitis, compared with injection of saline solution.

Incomplete ossification, especially Grades 1 and 2, is associated with a short gestation length. Foals with Grades 2 and 3 incomplete ossification were less likely to race and Grades 1, 2 and 3 earned around $30,000 less than their maternal siblings.