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 Medical Experiments that despite the use of microdosing, "animal studies will still be required". Guiding principles for more ethical use of animals in testing are the Three Rs (3Rs) first described by Russell and Burch in 1959. These principles are now followed in many testing establishments worldwide. Cell culture can be an alternative to animal use in some cases. For example, cultured cells have been developed to create monoclonal antibodies; prior to this, production required animals to undergo a procedure likely to cause pain and distress. However, even though cell or tissue culture methods may reduce the number of experiments