PITTSBURGH (AP) — The federal government has ordered the Pittsburgh Zoo & PPG Aquarium to have its human handlers stop using cattle dogs to cause "behavioral stress" to its elephants.

The inspection report by the U.S. Department of Agriculture was released Monday by People for the Ethical Treatment of Animals. PETA complained about the practice late last year and trumpeted the USDA decision.

"When elephants, dogs, and human handlers freely mix, everyone is in danger," Delcianna Winders, a lawyer for PETA, said in a statement. "PETA is calling on the Pittsburgh Zoo to switch to safe and modern elephant-management method — or, better yet, to retire the elephants to an accredited sanctuary where they'll be free from harassment for the rest of their lives."

According to the Jan. 7 inspection report, the zoo was ordered to immediately stop using the dogs in ways that upset the elephants.

Barbara Baker, the zoo's president and CEO, issued a statement saying: "The dogs read the behavior of the animals and alert the keepers to any disruption in the heard, preventing potential safety concerns for the staff and elephants. This method of animal management, in the livestock field, is referred to as a low-stress method."

Officials with the USDA's Animal and Plant Health Inspection Service visited the zoo on Jan. 6 and asked an unnamed manager to demonstrate how the dogs are used, according to the report.

The manager called one dog "to create a barrier between the husbandry staff and an elephant which had reached its trunk through the enclosure bars," the report said. "The dog showed aggressive behavior, growling and lunging at one elephant and entering its enclosure before being called back by the manager."

"The manager also reported the dogs' having bitten the elephants doing the course of their work," the report said. A television news clip from May, which was verified by zoo officials, "showed the elephants exhibiting signs of distress when charged by one of the dogs, including ear flapping, trumpeting, and turning and running away," the report said.

The USDA report said the zoo must control the elephants without causing them "behavioral stress" and ordered the change "from this point forward." The USDA didn't return calls seeking additional comment on the agency's findings.

Baker said that during the inspection, "our elephant manager demonstrated a drill simulating the dog's response to a keeper being in an extreme and unlikely situation. We showed how valuable the dogs can be should a keeper's safety be in question."

Zoo officials started using Australian cattle dogs to help handlers control the elephants in 2012 and Baker said that, since then, no dogs, elephants or handlers have been harmed.

But PETA contend zoos should use barriers to separate handlers and elephants at all times and use only positive reinforcement to control elephants. Zoo officials have said they don't punish their elephants for not complying with human handlers and use only positive reinforcement to control their behavior.

Baker said the zoo has also begun working with the USDA on a study "that examines a variety of facets regarding the welfare of elephants, including a unique examination of stress."

The USDA also noted that a sea lion at the aquarium had swollen corneas from too much chlorine in her water, and that a zoo veterinarian determined most "marine mammals have had issues with corneal disease" likely caused by too much chlorine. The zoo was supposed to have addressed that by Jan. 21, the report said.