Measuring Temporal Patterns of the Nest-Building Process in Mice for Animal Welfare and Disease Monitoring

Nesting behavior in rodents, used to assess animal welfare/illness and instrumental tasks, is also proposed as valuable for disease monitoring, evaluating potential risk factors and interventions. The reliability of Deacon’s 5-point ordinal scale to score nests at 24 h is well-recognized. However, previous work with the 3xTg-AD mice model of Alzheimer’s disease proposed a 3-day protocol to discard false negatives, thus unveiling genotype-, sex- and age-dependent differences. Here, we propose the size of nesting as a numeric variable, complementary to the ordinal scale, to allow parametric repeated measures analysis for identifying and evaluating temporal patterns in the nest-building process. Thus, nests of male and female mice with normal and AD-pathological aging ‘measured’ during 3-days showed that the nest-building process responded to a linear equation in wild-type animals or when female sex was considered but disrupted in males or the AD-genotype. Genotype per sex interaction indicated the optimal nest-building process in wild-type females, as they build the best nests at 72 h and the worst nests in 3xTg-AD mice at 48 h. On each day, data were consistent with the ordinal scale, but the identification of temporal patterns with the numeric variable confirmed nest-building as a complex process, which is sensitive to sex and genotype