Health status of experimental pigs

Due to the increase in the use of pigs in research, there seems to be a demand from the scientific community for an improved quality of experimental pigs. Germ-free pigs may be produced by removing fully developed foetuses aseptically from the uterus by hysterectomy and rearing them in isolators, alternatively embryo transfer may be used. Such rederived pigs may be maintained in isolators in the gnotobiotic status or gnotobiotic pigs may be used for the upstart of a breeding colony housed under conditions (i.e. a barrier) protecting them against certain agents, for which a monitoring system is operated. Different categories of barrier-bred pigs, such as, minimal disease, specific pathogen-free and microbiologically defined, are presented and differences between these categories are discussed. Basic principles of health monitoring in pigs, e.g. sample size, testing frequency and methods, are outlined. It is discussed how the lack of positive findings in health monitoring may be due to other factors than freedom from infection, e.g. treatment with antibiotics or a statistically invalid examination. Finally, the risk of infection with certain porcine agents when housing barrier-bred pigs in conventional experimental units is discussed.