Thermoregulation in young adult rats during short- and long-term protein malnutrition

Energy metabolism and thermoregulation were evaluated in malnourished (6% casein diet) or control (25% casein diet) young adult male Sprague-Dawley rats. After 1 week offered the diet, malnourished animals showed a decreased body weight, oxygen consumption (VO2) expressed per unit of body mass [milliliters O2/(gram X hour)] or per unit body surface [milliliters O2/(kilograms body weight0.75 X minute)] and food intake when compared to control animals. Rectal temperature was unchanged while ear temperature was slightly reduced in the protein-deprived animals. As malnutrition progressed, VO2 increased, reaching values significantly higher than controls by week 3. Oxygen consumption then decreased and by week 6 remained slightly higher (but not significantly) than in controls. Food intake followed to some extent changes in VO2. Rectal and shell (paws and tail) temperature measured in room temperature (range 24-25 degrees) showed the following changes: rectal temperature increased after week 1 of malnutrition to values significantly higher than controls and remained so until week 4, after which they declined to values still higher (but not significantly) than controls. Shell temperature in the malnourished animals was lower than in controls throughout the experiment. Exposure to a mild cold challenge (18-19 degrees) significantly increased VO2 and decreased body temperature in malnourished animals to a greater extent than in controls.