Effects of recombinant equine growth hormone on in vitro biomechanical properties of the superficial digital flexor tendon of Standardbred yearlings in training.
Authors: Gerard Mathew P, Hodgson David R, Rose Reuben J, Walsh William R
Journal: Veterinary surgery : VS
Summary
# Editorial Summary This 2005 study investigated whether recombinant equine growth hormone (rEGH) could improve the mechanical strength of the superficial digital flexor tendon (SDFT) in young racehorses undergoing training. Twelve Standardbred yearlings completed a 12-week high-speed treadmill training protocol; six received daily intramuscular injections of rEGH (escalating from 10 to 20 microg/kg) whilst controls received saline, after which SDFT tissue from both groups was mechanically tested to failure using controlled distraction. The rEGH-treated horses demonstrated significantly *lower* yield and ultimate tensile stress compared to controls, with trends towards decreased stiffness and increased strain, suggesting the hormone actually compromised rather than enhanced tendon mechanical properties. For practitioners involved in young horse conditioning and veterinary surgeons considering growth hormone supplementation, these findings carry important implications: using rEGH at manufacturer-recommended doses during the critical training phase of skeletal maturation does not strengthen the SDFT and may increase vulnerability to strain injury by reducing the tendon's capacity to resist tensile loading.
Read the full abstract on PubMed
Practical Takeaways
- •rEGH supplementation at standard doses will not improve tendon strength or resilience in young horses in training—don't expect it to prevent tendon injuries or enhance performance
- •If anything, rEGH may make tendons slightly weaker (lower tensile stress), suggesting it does not enhance physiologic adaptation to exercise stress
- •Focus instead on appropriate training schedules, farriery, and conditioning to develop strong, functional tendons in young Standardbreds
Key Findings
- •Yield and ultimate tensile stress were significantly lower in rEGH-treated horses compared to controls (P ≤ 0.05)
- •Recombinant equine growth hormone showed a trend toward increased maximal displacement and ultimate tensile strain but decreased tendon stiffness
- •rEGH administration at manufacturer-recommended doses did not significantly improve in vitro biomechanical properties of the forelimb SDFT in exercising yearlings
- •Tensile stress correlated significantly with both cross-sectional area and stiffness at yield and failure points