title: Age-related differences in food intake, body weight, and survival of male F344 rats in 5 degrees C cold.
abstract: Male F344 rats, 3, 12 and 21 months old, were acclimated at 5 degrees C for 7 to 9 weeks. Controls were maintained at 23 degrees C. Food intakes and body weights were monitored weekly. All animals in these age groups survived. However, 25-month-old rats placed in 5 degrees C for 3 weeks had only a 46% survival. All age groups responded to 5 degrees C exposure by different but always significant increases in food intake. Peak food intake was 100% above basal in the 3- and 21-month-olds and 80% above the basal in the 12-month-olds. These increases were sufficient to maintain body weights in the 3- and 12-month-olds, but in the 3-month-olds growth was retarded. The 100% increase of food intake in the 21-month-olds was not adequate to maintain body weight. The 25-month-old rats also increased their food intake significantly in cold, but large weight loss incurred in both the survivors and the non-survivors. Food intake and energy efficiency were different at different ages and under different environmental conditions in male F344 rats.
mesh_terms: D000222:Adaptation, Physiological; D000375:Aging; D000818:Animals; D001835:Body Weight; D003080:Cold Temperature; D002149:Energy Intake; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D011919:Rats, Inbred Strains; D013045:Species Specificity