Thermographic monitoring of nestsvof nude mice in their early life: technical note

We hypothesized to use Infrared Thermographic Technique (IRT) to detect the phenotype of athymic Nude-Foxn1 nu/nu and nu/þ mice from the very first hours of life, assuming that the presence (in nu/þ mice) or absence (in nu/nu mice) of hair follicles could completely shield or partially reduce the emitted radiation. The experimental phase of three months was carried out at the IRCCS Istituto Mario Negri in Milano, in compliance with institutional guidelines and international laws. Were used: Mice: 3 females Hsd: Nude-Foxn1nu athymic (nu/þ) 6 weeks of age and 3 males Hsd: Nude-Foxn1nu athymic (nu/nu) 6 weeks of age; Cages: 3 IVCages working under positive pressure, at 75 air changes/hour; Bedding: autoclaved hard wood; Food (Standard Diet Harlan) and water (autoclaved tap water) were administered ad libitum. Hood Laminar Flow: CS5 changing station. Nesting material: autoclaved wooden wool (aspen). Thermographic measurements were conducted 2 times per day (10:00 and 14:00) starting from day 0 (day of birth) to day 5 in 2 nests (40 images in 10 minutes). For each shot the camera detects two image formats: “.IRI” (thermography) and “.JPEG” (visible) as a control. The instrument display allows to see in real time the quality of thermographic images thus we preferred to make the filming manually instead of automatically in order to optimize the image’s quality. Statistical analysis was performed on the data obtained by the nests at different ages: day 0, 1, 2, 3, 4 and 5. We were not able to distinguish between nu/nu and nu/þ mice because they stayed all huddled together but we observed an increase in nests temperature between day 0 and day 5 where animals, mainly nude pups, are mostly exposed to heat loss. In absence of effective thermogenic processes, the higher temperature measured in 5 days old nests can be attributed to animals body size. The physiological thermoregulation (BAT activity) and behavioral thermoregulation (huddling) do not allow autonomy thermoregulatory but help to slow the dissipation heat; the only way that the 0 - 5 days old pups can increase their body temperature is the transmission of heat from parents. In this paper we have provided clear and replicable data about the usefulness of IRT in animal welfare monitoring.