Mark Purdey animal feed dates back to at least 1926. In the 1970s attention was directed within MAFF to the danger that this practice would result in the spread of infectious diseases. The diseases considered were those caused by conventional viral and bacterial organisms. No consideration appears to have been given to the risk that scrapie might be recycled in sheep, or even transmitted to other farm animals. This may seem surprising. The answer probably lies in the fact that half a century had elapsed without any indication that animal feed containing ovine protein was infecting sheep or any other animal." Purdey
Alternatives to animal testing create a model of the human immune system on which the efficacy of new vaccines and other compounds may be tested, replacing some steps of the vaccine development process that would otherwise be performed on animals. This process is faster and more flexible than previous methods but critics worry that it may be too simple to be useful on a large scale. Examples of computer simulations available include models of asthma, though potential new medicines identified using these techniques are currently still required to be verified in animal and human tests before licensing. Computer operated mannequins, also known as crash