Ambient temperature and ketone body plasma concentration in fasting geese

The effect on ketonemia of alternate exposure to ambient temperatures (Ta) of 25 and 5°C was investigated in fasting geese. Three experimental birds were compared to three controls continuously exposed to 25°C Ta while fasting. During the first 9 days of fasting, when both groups were exposed to 25°C, plasma concentration of -hydroxybutyrate (-OHB) increased similarly in both, from 0.10±0.02 to 6.62±0.71 mmol·L^–1. It later plateaued at 8–9 mmol·L^–1 in the control birds. When the experimental birds were exposed to 5°C Ta between the 9th and 15th day of the fast, it increased further during the first 24 h but thereafter decreased of 57%, from 8.62±1.56 to 3.73±1.24 mmol·L^–1. This decrease was reversed within the 6 days of return to 25°C Ta. In both groups, plasma acetoacetate (AcAc) concentration remained very low during the fast: 51±1 mol·L^–1. This reversible cold-induced effect on ketonemia may be used for investigating the possible role of ketone bodies in protein sparing during fasting.