Oxytetracycline as a Treatment for Contracted Tendons in Foals

Contracted tendons are a common issue that occurs in newborn foals. In mild cases, the problem often resolves on its own in a short period. In more severe cases, intervention and therapy may be required. One therapy veterinarians can apply is the use of an intravenous antibiotic called oxytetracycline.

Contracted tendons are a congenital flexural deformity that occurs when the foal’s tendons are too tight or short for the foal’s legs. All horses have two major tendons running directly behind their cannon bone (the large bone between the horse’s knee and fetlock). They are appropriately named the superficial and deep digital flexor tendons. Because the deep tendon attaches to a bone inside the horse’s hoof, if it is contracted or shortened, it causes the foal’s leg to curl up beneath itself, which is exactly what happens in cases of contracted tendons.

The prognosis for newborn foals with contracted tendons is good. In moderate cases, veterinarians can correct the deformity in many ways, such as prescribing controlled periods of exercise and rest or, in some cases, using aids like special shoes with toe extensions or leg splints. All foals with contracted tendons should be monitored closely to ensure their reduced mobility does not hinder efforts to stand, nurse, and consume adequate nutrition and hydration.

In severe cases, the foal will have considerable difficulty standing, walking, and nursing unaided. These cases require round-the-clock care and may benefit from oxytetracycline treatment. The viability of treating contracted tendons with an antibiotic may sound odd, but it has been used with much success in horses, often yielding rapid results. Research has shown that oxytetracycline prevents the influx of calcium ions into the muscle fibers, allowing the tendon to relax.

Despite its therapeutic potential, administering oxytetracycline is not without risks. There have been reported cases of acute kidney injury associated with oxytetracycline administration, highlighting the nephrotoxic effects that can arise, especially if this antibiotic is used excessively or without proper hydration in foals. The risk of renal impairment underscores the necessity for veterinary practitioners to exercise caution when administering oxytetracycline and to monitor the foals closely for any signs of adverse reactions. Additionally, oxytetracycline's role in promoting tendon relaxation must be balanced against these potential drawbacks, necessitating careful consideration regarding dosage and monitoring of renal function during treatment.

References

Ellero, N., Freccero, F., Lanci, A., Morini, M., Castagnetti, C., & Mariella, J. (2020). Rhabdomyolysis and acute renal failure associated with oxytetracycline administration in two neonatal foals affected by flexural limb deformity. Veterinary Sciences, 7(4), 160. https://doi.org/10.3390/vetsci7040160

Woodie, J. Protocols for Foals with Contracted Tendons. Online Article. May 5, 2017

Arnoczky, S. P., Lavagnino, M., Gardner, K. L., Tian, T., Vaupel, Z. M., & Stick, J. A. (2004). In vitro effects of oxytetracycline on matrix metalloproteinase-1 mRNA expression and on collagen gel contraction by cultured myofibroblasts obtained from the accessory ligament of foals. American journal of veterinary research, 65(4), 491–496. https://doi.org/10.2460/ajvr.2004.65.491