S Plevin1, J McLellan. 1. Florida Equine Veterinary Associates, Florida, USA.
Abstract
REASONS FOR PERFORMING THE STUDY: Limited information exists regarding the prognosis for juvenile racehorses sustaining injury to the suspensory ligament branch insertion (JISBI). OBJECTIVES: To investigate the effect of JISBI on racing performance; and to assess whether the severity of JISBI is prognostically important. STUDY DESIGN: Retrospective cohort study. METHODS: Records were reviewed for 896 juvenile Thoroughbreds in training, to identify horses with JISBI limited to one branch (cases). The ability of cases to start a race was compared to their cohorts. Race records of maternal siblings were compared to cases. RESULTS: The prevalence of JISBI for this population was 9.5%. Cohorts were 3.2 times more likely to start as a 2-year-old and 3.6 times more likely to start as a 3-year-old compared to horses with JISBI. Of 58 cases that were compared to maternal siblings, the total earnings per start (EPS), 2- and 3-year-old EPS were all reduced (P<0.01). Cases raced a mean of 3.8 times compared to 7.4 races for controls over the study period and were 113.2 days older by the time of first start (P<0.01). 'Speed figures' and EPS were, however, similar between cases that had raced and controls. Cases with a moderate-severe lesion (≥ Grade 2) were at significantly greater risk of reinjury than mild cases (P<0.05). CONCLUSIONS: JISBI causes decreased racing ability as a 2-year-old. Mild cases perform similarly to controls by their 3-year-old season, but more severe cases demonstrate reduced ability as a 3-year-old, with an increased likelihood of reinjury. Although the wastage was higher in case horses with JISBI, individual cases that make it to a race have similar earnings per start as their controls.
REASONS FOR PERFORMING THE STUDY: Limited information exists regarding the prognosis for juvenile racehorses sustaining injury to the suspensory ligament branch insertion (JISBI). OBJECTIVES: To investigate the effect of JISBI on racing performance; and to assess whether the severity of JISBI is prognostically important. STUDY DESIGN: Retrospective cohort study. METHODS: Records were reviewed for 896 juvenile Thoroughbreds in training, to identify horses with JISBI limited to one branch (cases). The ability of cases to start a race was compared to their cohorts. Race records of maternal siblings were compared to cases. RESULTS: The prevalence of JISBI for this population was 9.5%. Cohorts were 3.2 times more likely to start as a 2-year-old and 3.6 times more likely to start as a 3-year-old compared to horses with JISBI. Of 58 cases that were compared to maternal siblings, the total earnings per start (EPS), 2- and 3-year-old EPS were all reduced (P<0.01). Cases raced a mean of 3.8 times compared to 7.4 races for controls over the study period and were 113.2 days older by the time of first start (P<0.01). 'Speed figures' and EPS were, however, similar between cases that had raced and controls. Cases with a moderate-severe lesion (≥ Grade 2) were at significantly greater risk of reinjury than mild cases (P<0.05). CONCLUSIONS: JISBI causes decreased racing ability as a 2-year-old. Mild cases perform similarly to controls by their 3-year-old season, but more severe cases demonstrate reduced ability as a 3-year-old, with an increased likelihood of reinjury. Although the wastage was higher in case horses with JISBI, individual cases that make it to a race have similar earnings per start as their controls.