The impact of reduced frequency of cage changes on the health of mice housed in ventilated cages

Abstract

SummaryOur purpose in this investigation was to determ ine if we could reduce cage changing frequency without adversely affec ting the health of mice. We housed mice at three different cage changing frequencies: 7, 14, and 21 days, each at three different cage ventilat ion rates: 30, 60 and 100 air changes per hour (ACH), for a total of nine experimental conditions. For each condition, we evaluated the health of 12 breeding pairs and 12 breeding trios of C57BL = 6J mice for 7 months. Health was assessed by breeding performance, weanling weight and growth, plasma corticosterone levels, immune function, and histological examinat ion of selected organs. Over a period of 4 months, we monitored the cage microenvironment for ammonia and carbon dioxide concentrations, relative humidity, and temperature one day prior to changing the cage. T he relati ve humidity, carbon dioxide concentrations, and temperature of the cages at all conditions were within acceptable levels. Ammonia concentrations remained below 25 ppm (parts per million) in most cages, but, even at higher concentrations, did not adversely affec t the health of mice. Frequency of cage changing had only one signi®cant effect; pup mortal ity with pair mat ings was greater at the cage changing frequency of 7 days compared with 14 or 21 days. In additi on, pup mortality with pair matings was higher at 30 ACH compared with other ventilat ion rates. In conclusion, under the conditions of this study, cage changes once every 14 days and ventilation rates of 60 ACH provide optim um conditions for anim al health and practical husbandry.

Housing breeding mice in three different IVC systems: maternal performance and pup development

“…However, it is also important to consider the optimal microclimate for the growing pups. ReebWhitaker et al 5 found that, although more pups survived, they had lower weaning body weights at 100 ACH than at 30 ACH, which might indicate a too cold environment for them. These pups did not have access to nesting material which is important for modulating the microclimate and likely reduces the cooling effect on them.…”

“…Several studies have assessed the levels of CO 2 and NH 3 , relative humidity (RH) and temperature in the cages with different cage changing intervals, air changes per hour (ACH) and population densities in the cages. [2][3][4][5][6][7] However, the effect on animals housed in this type of cage environment has just started to be evaluated in recent years. Studies have shown that rodents in general prefer non-ventilated cages to ventilated ones, that they prefer cages with the lowest number of ACH, and larger cages to smaller ones.…”

Long-term effects of cage-cleaning frequency and bedding type on laboratory rat health, welfare, and handleability: a cross-laboratory study

“…In the long term, frequent cleaning causes chronic stress in mice; more frequent cleaning reduces weight gain (Beynen & Vantintelen 1990) and increases pupmortality (Reeb-Whitaker et al 2001, Peters et al 2002. If lower cleaning rates benefit rodents, their application would also be more economical for animal units, leading to less waste and reduced workloads for technicians.…”

A Quick Method to Assess Rodent Cage Ammonia Levels

“…Even when not clinically recognized, elevated ammonia may significantly affect drug studies and liver function [11] and may contribute to elevated corticosterone values [9]. Excessive ammonia accumulation emerges with reduced cage changing frequency [10], in the presence of inadequate ventilation [9,12], under conditions of higher humidity, and with increased animal densities or nitrogen load [13]. Certain bedding types accentuate ammonia production [14,15] while excessive ventilation rates may affect breeding success (Wimsatt, unpublished data).…”