Penn also had the highest number of violations of federal law governing animals' care, including many repeat violations and the discovery by inspectors of a dead puppy under a grate, according to a survey of Ivy League schools by a Washington, D.C., physicians group.
In a review of inspection reports from 2008 to 2011 by the Agriculture Department, which regulates research facilities that use animals, the Physicians Committee for Responsible Medicine (PCRM) found that the eight Ivy League universities had what it called "disturbingly high numbers of Animal Welfare Act violations," many of which were repeat or severe.
Penn, which houses up to 5,000 animals a year at its medical and veterinary schools, racked up 115 violations since 2008, more than double the number of violations found at Princeton University, the second worst-ranked school in the survey.
In one incident at Penn, a newborn puppy was found dead, trapped beneath a floor grate. The puppy had slipped through the grate unnoticed, and an unknown amount of time passed before his death. In another incident, three gerbils died when water was just out of their reach due to unsuitable sipper tubes. All of these deaths could have been prevented, the group said.
On multiple occasions, investigators also found that a barn holding cows had an accumulation of feces and urine, and researchers deviated from approved protocols.
In one visit to the school, government inspectors found that a dog was housed alone for two days without positive human contact or contact with other dogs.
Piglets and ferrets were also found living on flooring with holes large enough for their feet to slip through, and horses lived in potentially dangerous enclosures with missing boards, exposed nails, and sharp edges, among other violations.
In an e-mail response, Penn said "we take these issues very seriously and have modified our program to correct the deficiencies noted during that period. We are continually working to improve our animal care program with the goal to eliminate any shortcomings that occur and prevent them from recurring.
"The University has had a good and long-standing record of compliance with the provisions of the Animal Welfare Act," the statement said. "Nothing less than the highest standards for the conduct of research are acceptable."
The physicians group said it focused on the Ivies because of their "prestige" and what it called their "disproportionate" amount of federal research funding.
Penn receives the highest amount of federal research funding of any Ivy League school: $1.4 billion from the National Institutes of Health since 2008, according to the report. Its lead author, John J. Pippin, is a Dallas cardiologist.
The group said the USDA should formally sanction the schools for violations and it wrote to NIH asking the agency to pull research funding from the offending institutions.