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 degrees C was investigated in fasting geese. Three experimental birds were compared to three controls continuously exposed to 25 degrees C Ta while fasting. During the first 9 days of fasting, when both groups were exposed to 25 degrees C, plasma concentration of beta-hydroxybutyrate (beta-OHB) increased similarly in both, from 0.10 +/- 0.02 to 6.62 +/- 0.71 mmol X L-1. It later plateaued at 8-9 mmol X L-1 in the control birds. When the experimental birds were exposed to 5 degrees 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 X L-1. This decrease was reversed within the 6 days of return to 25 degrees C Ta. In both groups, plasma acetoacetate (AcAc) concentration remained very low during the fast: 51 +/- 1 mumol X 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.