Effects of semi-starvation on the total body composition and absorptive function of the small intestine of the young adult female rat

Calorimetric measurements made on rats during repeated periods of weight gain and weight loss

1. Rats in respiration chambers were grown for 32 days and their weight reduced by 27-40% on three occasions and realimentated. After the first cycle rats lost body weight more rapidly and regained that weight more quickly than previously. 2. The initial growth phase took 32 days compared with only 8 days in the final period. Each gram of weight gain was associated with 13-14 kJ of dietary net energy during the last two periods of realimentation compared with 19-20 kJ during the first period. 3. Calorimetric measurements showed that although maintenance energy requirement increased during the periods of growth, mean net availability of metabolizable energy was 0.91 compared to 0.60 during weight loss. 4. During the final period much of the weight gain was in the form of lean (67%) but the majority of energy retained was as fat (67-70%).

The efficiency of growth during body weight recovery in young adult female rats

1. Six young adult female rats were subjected to 40% body weight loss in 84 days by food restriction followed by recovery of body weight in 36.2 +/- 4.28 days by ad libitum food intake. The regimen was then repeated, with 40% body weight loss in 105 days followed by recovery of body weight in 22.8 +/- 2.00 days. 2. Food intakes were measured continuously. 3. These rats used digestible energy more efficiently during the second recovery (49.1 +/- 3.11 v. 77.3 +/- 7.91 kJ digestible energy intake per g body wt gain). 4. Seven rats were subjected to one body weight loss and recovery. Five of them had an efficiency of 44.1 +/- 3.34 kJ/g live wt gain which was not significantly different from that of the first group during their second recovery; they may not have been capable of improvement after a second deprivation. 5. It is concluded that some rats can adapt after a period of severe body weight loss and recovery to utilize food more efficiently during body weight recovery after a second episode.

Intestinal absorption of nutrients in rats treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

Impairment of active intestinal absorption of glucose and leucine was observed in rats 2-3 wk after oral treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (5 and 100 mg/kg). At the higher dose level used this response was complicated by the effects of severely reduced food consumption. Malabsorption of specific nutrients may help occasion the body wasting seen in many animals after acute exposure to TCDD.