Ammonia and CO2 in static cages

Static cages are a convenient means of housing rodents, although gases such as ammonia and carbon dioxide tend to accumulate in these cages rather quickly. A newly introduced disposable static mouse cage may reduce expenses and labor associated with the use of conventional reusable static cages. Silverman et al. investigated whether the two types of static cages differed in their capacity to dissipate carbon dioxide and ammonia. They housed groups of female mice in disposable and in reusable cages for 7 d and evaluated concentrations of ammonia and carbon dioxide in each cage daily. They then carried out a 'cage crossover' and repeated the experiment. The two cage types were similar in their ability to dissipate carbon dioxide and ammonia, which rose to high concentrations in all cages. See page 16

Enriching mouse breeding performance

In a previous study, Whitaker and colleagues showed that cage size had little effect on the reproductive performance and behavior of C57BL/6 mice. In this follow-up study, they added environmental enrichment into the mix. Breeding trios of mice were housed in cages of two different sizes (standard and large). Half of the cages of each size contained four enrichment items, and the remaining cages were barren. The authors measured several reproductive parameters and evaluated the behavior of a subset of weaned pups raised in each cage condition. Though cage condition did not clearly or consistently affect pups' performance in behavioral tests, enrichment (regardless of cage size) significantly benefited reproductive performance. See page 24

No need to bend over backwards

A standard method of identifying the gender of mouse pups involves measurement of the anogenital distance, which is greater in males than in females. This method, however, may be unreliable, particularly when pups are young and the animal handler is inexperienced. Wolterink-Donselaar et al. show that in pigmented mice, a pigment spot on the scrotum of male neonates can be used as a marker of gender. Female pups lack visible pigmentation in the anogenital region. Identifying this marker is a quick, easy and reliable technique for 'spotting' the gender of pigmented neonatal mice. See page 35