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Effect of feeding pattern on the energy metabolism of rats given low-protein diets

Published online by Cambridge University Press:  25 March 2008

K. J. McCracken
Affiliation:
Agricultural and Food Chemistry Research Division, Department of Agriculture and Queen's University, Newforge Lane, Belfast BT9 5PX
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Abstract

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1. The deposition of fat and protein and the utilization of energy by growing rats offered diets ad lib. or in controlled amounts by gastric intubation has been investigated. Diets contained 50, 75, 100 or 200 g protein/kg, mainly as casein

Gain of body-weight and protein increased with increasing dietary protein concentration when animals received the same energy intake, although the reverse was true for fat deposition. However, the differences in live-weight gain were almost entirely due to changes in body water. The dry-matter content of the gain in animals given low-protein diets was 770 g/kg compared to 360 g/kg in those given the control diet

2. Energy retention was unaffected by dietary protein level in groups given the same energy intake by gastric intubation. In Expt 1 daily heat production increased significantly (P < 0·05) with increasing protein level (50, 75 and 200 g protein/kg diet) when energy intake was constant, but in Expt 2 there was no significant effect of protein level (50, 100 and 200 g protein/kg diet). Problems arose in the selection of a suitable basis for comparison of heat production between groups because of the differences in body-weight and body composition

3. The energy requirement for zero energy balance was approximately 10% lower for the low-protein groups than for those given the diet containing 200 g protein/kg when food intake was just above the maintenance level. When the requirement was expressed per unit metabolic body size (W0·75 kg) dietary protein level had no significant effect. The mean values for Expts 1 and 2 were 452 and 436 kJ respectively

4. The energy cost of weight gain increased as dietary protein level decreased in pairs of groups gaining at the same rate. The extra energy ingested by the animals given the lower protein level was converted to body tissue with an efficiency of at least 0·70

5. Striking differences were observed in body composition and energy retention of the two pairs of groups used for the comparison of tube-feeding and ad lib. feeding. With the diet containing 50 g protein/kg, tube-fed rats gained significantly more weight (P < 0·01) and more fat, dry matter and energy (P < 0·001) than their ad lib. counterparts given an iso-energetic intake

6. The results demonstrate that dietary protein level has little or no effect on the utilization of energy by growing rats when the pattern of intake is controlled by gastric intubation.

Type
General Nutrition
Copyright
Copyright © The Nutrition Society 1975

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