Despite limited scientific understanding of the impacts on juvenile horses, extra-label use of bisphosphonates is anecdotally reported to be widespread. This study was conducted to determine the effects of clodronate disodium (CD), a specific bisphosphonate, on hormones associated with blood calcium regulation. Thirty-two yearling Quarter Horses were given either saline, 1-dose, 2-doses, or 4-doses of CD over the course of 168 d. Growth measurements (height, weight, and body measurements) and serum samples were collected throughout. Blood samples were analyzed for blood calcium and hormones associated with blood calcium. All physical measurements increased over time but were not affected by CD. Parathyroid hormone temporarily increased following a second dose in horses that received multiple doses. Ionized calcium concentrations decreased over time and growth hormone concentrations tended to decrease over time. The present study provides the framework for future research on the relationship between CD administration in juvenile horses and the endocrine regulation of calcium.

Read the full article in the Journal of Animal Science.