Many Americans may question the practice of scientifically experimenting on lab animals, but there's been a sharp rise in the number of animals used for such research, according to a new study.
A team at People for the Ethical Treatment of Animals (PETA), an animal welfare organization, found about a 72 percent increase in the number of animals being used in federally funded labs between 1997 and 2012 — mostly mice.
The average number of lab animals used in a year rose from 74,619 to 128,846 over those 15 years, the team reports in the Journal of Medical Ethics.
"Animal use data were obtained from species inventories — reporting the 'approximate average daily inventory' of vertebrate animals held at the institution — contained in the Animal Welfare Assurances filed at least once every four years by NIH-funded institutions," PETA'S Dr. Alka Chandna wrote in the report.
"Only one species (cats) showed a consistent decrease in use over time, but the decrease was only marginally significant," Chandna added.
"These patterns contradict industry claims of reduced animal use but are consistent with international trends in experimental use of animals in recent years that show an increased use of mice (mainly for gene modification purposes) and, in some cases, fish while reporting declines in the use of cats, dogs, primates, rabbits, guinea pigs and hamsters. Concerns about these trends have been raised by the general public, scientists and animal welfare community."
They noted that federal policies are discouraging the use of "higher" animals such as chimpanzees.
"This bias persists despite extensive evidence that — like dogs, cats and primates — animals such as mice, rats and fish experience pain, stress and distress, and suffer in laboratories and have complex social, emotional and cognitive lives," Chandna wrote.
An official at the National Institutes of Health disagreed with the findings.
"The article may be right on the numbers taken from the Animal Welfare Assurances, but those numbers do not accurately reflect the numbers of animals in use in research studies and thus we do not support the rationale and conclusions of the study," the NIH official said in a statement emailed to NBC News.