FDA recommends that you implement standard operating procedures that permit for adequate periods of quarantine and acclimation, as well as a program of socialization. Background levels of disease and psychological stress should be controlled as much as possible. Farm animals are particularly prone to intestinal parasites, which commonly present sub-clinically but can cause clinical syndromes under the stress of surgery and during recovery. To minimize this confounding factor, FDA recommends that you initiate early and frequent dialogue with the attending veterinarian about ways to detect and eliminate clinical and sub-clinical disease to ensure optimal animal wellness. FDA notes that the laws and policies of other agencies, e.g.,the Animal Welfare Act and Public Health Service (PHS) “Policy on Humane Care and Use of Laboratory Animals,” have resulted in important changes in the use of environmental and socialization protocols that are routinely implemented to control background stress. FDA believes that following these laws and policies enhances the opportunity for and intensity of observations and can potentially result in other useful findings for the investigators.