Nest-building performance in rats: impact of vendor, experience, and sex

Abstract

Nest building behavior has been intensely applied as a parameter for severity assessment in mice. In contrast, only a limited number of studies have reported nest building data from rats. Here, we assessed nest building in rats in two different facilities addressing the hypotheses that the vendor, previous experience with the nesting material as well as sex of the rats has an impact on the performance. Data from two study sites and three raters were compared to obtain information about the robustness of nest complexity scoring. The findings demonstrate a generally poor nest building performance in rats with a pronounced day-to-day fluctuation, and site-specific differences. Application of a newly developed scoring system resulted in an intermediate inter-rater reliability. Previous experience with the nesting material did not exert a consistent impact on nest complexity scores. Sex differences proved to depend on vendor and animal facility without consistent findings supporting a superior performance in female or male rats. In conclusion, our findings argue against a robust and consistent influence of sex and familiarity with the nesting material. The comparison between facilities suggests that local conditions need to be considered as influencing factors, which should be explored in more detail by future multicenter approaches. Considering the day-to-day fluctuation and the intermediate inter-rater reliability, we highly recommend to base nest complexity evaluation on means from several subsequent days analyzed by a group of experienced raters.

Toward evidence-based severity assessment in mouse models with repeated seizures: I. Electrical kindling

“…Another difference became evident when analyzing nestbuilding behavior in kindled rats and mice with compromised nest-building only observed in rats [58]. The higher sensitivity of nest building in rats might be related to the lower level of motivation to construct complex nest structures [59]. Related to their smaller body size, thermoregulation in mice depends more intensely on environmental factors, so that it might be that nest building is only affected at higher levels of distress in mice.…”

Where are we heading? Challenges in evidence-based severity assessment

“…59 Therefore, again, standardization is crucial as assessment protocols may vary between laboratories, resulting in the lack or changed manifestation of these behaviours (Schwabe et al, this issue; Jirkof et al, this issue). 60,61 Another motivational-or emotionaldriven behaviour, namely voluntary wheel running, has been utilized to assess the severity of experimental procedures. 62 Benefits include an observer-independent, automatized assessment of severity that has been proposed to serve as an indicator of disturbed wellbeing (Mallien et al, this issue).…”

“…61 In another study, scoring of nesting behaviour as predefined in the respective SOP had to be optimized to enhance inter-rater reliability (Schwabe et al, this issue). 60 Furthermore, effects of predictability and adaptation to procedures as well as effects of the chronology of procedures have to be taken into account. Repeated predictable stress will cause resilience against colitis-induced behavioural changes in mice and behavioural changes associated with learned helplessness do not occur if the stressor is controllable.…”

Phenotyping Young GluA1 Deficient Mice – A Behavioral Characterization in a Genetic Loss-of-Function Model

“…Considering nest building activity in young mice, there are two relevant studies examining the ability of young mice to build nests which show diverging results: An earlier report from Moy et al (2004) found relevant levels of nest building activity in mice aged 3-4 weeks, while Eltokhi et al (2020) detected no relevant nesting behavior in adolescent mice. However, a range of interfering factors have to be considered when interpreting nesting data, among others, body weight, strain and housing conditions (Bult and Lynch, 1997;Martin et al, 2016;Robinson-Junker et al, 2017;Schwabe et al, 2020). Considering burrowing activity, earlier studies indicated relevant burrowing activity in adolescent mice (Hart et al, 2012;McLinden et al, 2012;Eltokhi et al, 2020).…”