The University of Missouri is defending its research practices after a national pet-adoption group publicly decried an experiment that led to six female beagles being euthanized.

The California-based Beagle Freedom Project (BFP), which is suing the university system over $82,000 in fees it says it is being charged for an open-records request, said it learned of the dogs’ deaths after happening upon a published study about treatment for damaged corneas.

As detailed in April in the Journal of Veterinary Ophthalmology, the study said roughly 1-year-old beagles had their left eyes intentionally damaged while they were anesthetized. Half of the animals then were given a topical acid treatment to determine if that healed the eye damage. It didn’t, and the dogs eventually were put to death.

Kevin Chase, vice president of the BFP, which rescues former research animals ranging from ponies to goldfish for adoption, called the university’s experiment “a colossal failure” and “cruel,” noting the “cornea’s top layer is filled with thousands of tiny nerve endings.”

Animal-rights groups widely say nearly 400 U.S. research labs use nearly 70,000 dogs each year, the majority of which are beagles, usually because of their docility.

The university issued a statement saying the beagles were anesthetized during the procedure and were given pain medications if any discomfort was evident. The research, meant to develop painless or noninvasive treatments for corneal injuries, “improves the quality of life for both animals and humans,” the university said.

“Animal research is only done when scientists believe there is no other way to study the problem, and our researchers respect their research animals greatly and provide the utmost care,” the statement said. “The animals were treated humanely and every effort was made to ensure dogs were as comfortable as possible during the tests to study the effectiveness of the new drug treatment.”