Fig. 1

The experimental protocol, and body mass and food intake. A All animals were housed at an ambient temperature of 21 °C before the experiment started (day 0). The animals in 10 °C group were transferred into10°C for 14 days, and those in the 0 °C group were transferred into 0 °C for 14 days, during which the animals in 21 °C group were kept at 21 °C. At the end of day 14, half of the animals in each group were randomly selected for dissection, and the remaining animals were transferred into 30 °C from day 15 to 42 (referred to as 21–30 °C, 10–30 °C, and 0–30 °C groups). Body mass (BM) and food intake (FI) were measured on days 0–42. Gross energy intake (GEI), resting metabolic rate (RMR), non-shivering thermogenesis (NST), uncoupling protein 1 mRNA expression and cytochrome c oxidase (COX) activity of brown adipose tissue, as well as body fat content and serum T3 and T4 levels were measured on day 14 and 42, respectively. B Body mass on days 0–42; C body mass gain on day 14 and 42 relative to that on day 0; D food intake on days 0–42. Data are means ± s.e.m. *, significant difference between the groups (P < 0.05), **, P < 0.01, ns, non-significant difference (P > 0.05)