title: Castration eliminates conspecific aggression in group-housed CD1 male surveillance mice (Mus musculus).
abstract: Microbiologic surveillance is essential for murine health maintenance. At our institution, female progeny of inhouse-bred CD1 mice are used in both the transgenic facility and health-surveillance program. To reduce overall animal use, the male progeny, otherwise slated for euthanasia  due to a lack of utility, also were enrolled as sentinels. However, veterinary technicians noted excessive fighting among cohoused male surveillance mice that was not resolved by environmental enrichment. After review of factors known to influence aggression in male mice, early castration  was selected as the most likely approach to eliminate aggressive behavior among cohoused male mice. Male mice were castrated before 1 mo of age and then placed into the surveillance program. Each week, veterinary technicians recorded all incidences of fighting in cages of castrated and noncastrated  male surveillance mice to determine differences between groups. Over a 3-mo period, the overall prevalence of fighting in cages of intact male mice was 64% (14 of 22 cages); although all intact male mice were used preferentially for complete necropsy surveillance time points, one of these  cages required separation and 4 cages housed mice that incurred severe fight wounds requiring both separation and euthanasia. In comparison, a 0% (0 of 16 cages) prevalence of fighting was observed among castrated male mice. Castration eradicated pain and distress associated with fighting,  thereby constituting a refinement, and allowed the use of male mice from the breeding colony for surveillance, thereby reducing the total number of mice bred for surveillance. In conclusion, castration is a minimally invasive, safe, humane, rapid method to eliminate conspecific aggression  among male CD1 surveillance mice.
authors: Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. Lofgren@mit.edu
authors: Jennifer L S
authors: JL
authors: Lofgren
authors: Susan E
authors: SE
authors: Erdman
authors: Christine
authors: C
authors: Hewes
authors: Catrina
authors: C
authors: Wong
authors: Rebecca
authors: R
authors: King
authors: Tony E
authors: TE
authors: Chavarria
authors: Allan R
authors: AR
authors: Discua
authors: James G
authors: JG
authors: Fox
authors: Kirk J
authors: KJ
authors: Maurer
mesh_terms: D000374:Aggression; D000827:Animal Welfare; D000818:Animals; D000830:Animals, Laboratory; D001522:Behavior, Animal; D004777:Environment; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice / Q000502:physiology* / Q000523:psychology / Q000601:surgery*; D009919:Orchiectomy; D015995:Prevalence; D013047:Specific Pathogen-Free Organisms