title: Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 3. In vivo ultrasonographic assessment of the cross-sectional area and echogenicity of the superficial digital flexor tendon.
abstract: OBJECTIVE
  To determine if the superficial digital flexor tendon (SDFT) of young Thoroughbred horses changed in size and echogenicity in association with early race training.
  
  
  METHODS
  Cross-sectional area (CSA) and echogenicity were determined ultrasonographically at five levels of the SDFT of the forelimbs of 2-year-old fillies (n=14), corresponding to 4, 8, 12, 16 and 20 cm distal to the accessory carpal bone (DACB). Measurements were made before and after a 13-week period in which a trained group of seven horses was compared with another group of seven untrained horses.
  
  
  RESULTS
  Level below the accessory carpal bone had a significant effect on CSA and Level 8 was smaller than all other levels except Level 12, while Level 12 was smaller than Levels 4 and 20 but not different from Levels 8 and 16. There was a significant interaction between level and time due to effects observed at Level 8. The CSA at Level 8 measured pre-training was different from that of Levels 4 and 20 in both pre- and post-training groups (p<0.05), but when measured post-training was not different from any other measurement. There was also a significant interaction between treatment group and time. There was no difference between CSA for the untrained and trained groups at the pre-training observation (p=0.9), but post-training the CSA (pooled over all levels) in trained horses was significantly larger than that of the untrained horses both post-training (p=0.019) and pre-training (p=0.034), and was not different from the pre-training CSA recorded in the trained group (p=0.29). Treatment group had no effect on echogenicity (p=0.43), while echogenicity was less at the end of the trial in both trained and untrained horses (p<0.001).
  
  
  CONCLUSIONS
  Early training for racing was associated with an increase in mean CSA of the SDFT. Other factors such as age and maturity may play a role in limiting this increase.
authors.affiliation: Epicentre, Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
authors.forename: N R
authors.initials: NR
authors.lastname: Perkins
authors.forename: C W
authors.initials: CW
authors.lastname: Rogers
authors.forename: E C
authors.initials: EC
authors.lastname: Firth
authors.forename: B H
authors.initials: BH
authors.lastname: Anderson