The contribution of body protein to the supply of energy in starved newborn piglets is not preferentially suppressed by intravenous provision of glucose and fat.

Newborn piglets were used to study body protein preservation because it is critical to the survival of premature infants. Quantitative estimates of endogenous fuel use were obtained from 12 to 72 h of age in male piglets. Of the 40 piglets used (1300 +/- 205 g, mean +/- SD), 16 served as a 12-h-old body composition reference (R), 16 were starved (S) and received water only, and 8 received supplemental energy (E), obtaining 70% [210 kJ/(kg x d)] of their resting energy requirement as an i.v. mixture of glucose and Intralipid (65:35 energy ratio). Urine was collected continuously from the bladder via an umbilical urachal catheter. Total body water, glycogen, lipid, ash, and Kjeldahl-N were determined on whole-pig homogenates. Comparative slaughter was used to estimate the disappearance of body constituents of S and E pigs from 12 to 72 h of age. Midpoint body weight was used in these calculations. Supplemental energy decreased use of all body energy sources as indicated by the decrease in body dry matter disappearance, 41.6 +/- 8.8 vs. 25.5 +/- 5.9 g/kg (P = 0.0021) and protein (urinary N excretion), 995 +/- 508 vs. 329 +/- 135 mg/kg (P = 0.0119) over 60 h. Supplemental energy did not preferentially spare the percentage of the resting energy expenditure supplied by endogenous body protein (protein 37.6% +/- 9.6 vs. 41.7% +/- 10.4; lipid 25.7% +/- 5.2 vs. 20% +/- 4.1; glycogen 36.8% +/- 7.5 vs. 38.3% +/- 9.9; S vs. E) because it made up approximately 40% of the total in food-deprived and supplemented piglets.