Recombinant Equine Growth Hormone does not Affect the In Vitro Biomechanical Properties of Equine Superficial Digital Flexor Tendon

OBJECTIVE: To evaluate the effect of recombinant equine growth hormone (rEGH) on the in vitro biomechanical properties of normal adult equine superficial digital flexor tendon (SDFT). STUDY DESIGN: Completely randomized design. SAMPLE POPULATION: Nine Standardbred horses, 6 to 9 years of age with ultrasonographically normal forelimb SDFT. METHODS: Six horses were administered intramuscular (IM) rEGH at 10 microg/kg/day for 1 week, and then 20 microg/kg/day for another 5 weeks; 3 horses (control subjects) were administered an equivalent daily volume of sterile water IM. Horses were killed at the end of the 6-week treatment period, and both forelimb SDFT were harvested and stored at -70 degrees C. In vitro biomechanical testing was performed under uniaxial tension. Results were analyzed using a general linear model of analysis of variance; significance was set at P <.05. RESULTS: There were no differences in cross-sectional area, maximal load at failure, yield load, ultimate and yield tensile strain, ultimate and yield tensile stress, or stiffness between tendons from control and treated horses. CONCLUSIONS: Administration of rEGH to adult Standardbred horses for 6 weeks had no detectable effect on the in vitro biomechanical properties of normal SDFT. CLINICAL RELEVANCE: Administration of rEGH does not modulate the in vitro biomechanical properties of SDFT from adult Standardbred horses.