Buyers of horses at North America’s three largest auction companies will be able to request that horses at the sale be tested for bisphosphonates, a class of drugs that are approved for use in older horses to treat osteoporosis but that have also been rumored to have been abused in young horses headed for the sales ring, the three companies announced on Monday. The three companies – Keeneland, Fasig-Tipton, and Ocala Breeders Sales Company – said that buyers who request the tests will be able to return horses to consignors if a horse younger than 4 years old tests positive for any of the drugs in the class. The buyer will be responsible for the $500 cost of the test, but that cost will be borne by the consignor if a horse tests positive, the sales companies said. Racing regulators have issued concerns about the use of bisphosphonates in young horses after reports of their administration to young horses prior to sales in order to build bone density. The drugs can have long-lasting effects in horses, and some medical practitioners have claimed that the drugs can lead to fractures due to changes in bone remodeling processes that can be detrimental to young horses. The companies implemented the policies in the wake of a recent spate of catastrophic injuries in horses at Santa Anita that have led to widespread criticism of the racing industry. Though regulators have not yet announced any findings from studies of the deceased horses, the deaths have renewed calls for the racing industry to review its medication practices. Bisphosphonates are approved for use in horses 4 years old or older, but the FDA has also included warnings about the long-term use of the drug in younger horses, saying that the drugs can inhibit the ability of a horse to repair “microdamage” of the bone, especially when used at high doses or for long periods of time. Reports of the use of bisphosphonates on young horses emerged within the last five years. The American Association of Equine Practitioners has issued warnings in recent years about use of the drugs in young horses, and earlier this year, the equine medical director of the Kentucky Horse Racing Commission, Dr. Mary Scollay, said that commission staff had begun looking into the drugs. The Consignors and Commercial Breeders Association called the off-label usage of bisphosphonates in younger horses "unacceptable" in a statement issued Saturday. "The Consignors and Commercial Breeders Association (CBA) and its members are first and foremost concerned about equine health," the statement read. "The recent tragedies in California have led to a full examination of how our industry cares for horses from the moment a foal hits the ground all the way up until an injury occurs. Conclusions have been made that the use of bisphosphonates in horses younger than 4 years old has led to unintended and dangerous side effects that weaken our equine athletes. While it is believed that the rate of usage in foals and yearlings has been limited, the CBA believes any 'off label' use of bisphosphonates in young horses is unacceptable." The sales companies said in a release that the they would implement the policy beginning on July 1, which would cover the yearling and breeding stock sales in the latter half of the year. “This is an integrity issue,” the presidents of the companies said in a joint statement. “We all agree that this policy is critical to strengthen buyer confidence in the entire Thoroughbred auction process.”