Which piece of evidence would best support reason #2? Animal research is extremely costly, so it is in the best financial interest of scientists to pursue other means of testing before deciding to utilize animals in their research. With just 115 inspectors and over 7,500 facilities involved with the research, breeding, or handling of animals in some way, regulation of the Animal Welfare Act is virtually impossible. Enacted in 1966, the Animal Welfare Act is a US federal law that regulates the care and use of animals in a variety of circumstances, including medical research and testing. People will not tolerate the suffering of animals, so it is only logical that scientists will only use animal testing as a last resort when all other measures have failed.