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
Animal welfare of Agriculture Animal and Plant Health Inspection Service (APHIS) enforces the Animal Welfare Act. APHIS inspects animal research facilities regularly and reports are published online. According to the U.S. Department of Agriculture (USDA), the total number of animals used in the U.S. in 2005 was almost 1.2 million, but this does not include rats, mice, and birds which are not covered by welfare legislation but make up approximately 90% of research animals. There are many different approaches to describing and defining animal welfare. Positive conditions - Providing good animal welfare is sometimes defined by a list of positive conditions which