Effects of Nesting Material on Energy Homeostasis in BALB/cAnNCrl, C57BL/6NCrl, and Crl:CD1(ICR) Mice Housed at 20 °C.

Discrepancies exist between the preferred temperature range for mice (26 to 32 °C) and current recommendations (20 to 26 °C), which may alter metabolism and negatively affect studies using mice. Previous research indicates that nesting material can alleviate cold stress in mice; therefore, we sought to determine the effects of the amount of nesting material provided (0, 6, or 12 g) on heat energy loss and energy balance in 3 mouse strains housed at currently recommended temperatures during the daytime, a period of presumed inactivity. Groups of BALB/cAnNCrl, C57BL/6NCrl, and Crl:CD1(ICR) mice, balanced by strain and sex, were group-housed and provided 0, 6, or 12 g of nesting material. After a 3-d acclimation period, body weight was determined daily at 0800, food intake was determined at 0800 and 2000, and total heat production was evaluated from 0800 to 2000 on 4 consecutive days and used to calculate energy balance and the respiratory quotient. Although the amount of nesting material had no overall effect on food intake or heat production, mice provided 12 g of nesting material had greater weight gain than those given 0 or 6 g. This increase in body weight might have been due to improved energy balance, which was corroborated by an increased respiratory quotient in mice provided 12 g of nesting material. In summary, although heat production did not differ, providing 12 g of nesting material improved energy balance, likely leading to an increase in body weight during the 0800-2000 testing period.