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We previously showed that parenteral nutrition (PN) compared with formula feeding results in hepatic insulin resistance and steatosis in neonatal pigs. The current aim was to test whether the route of feeding (intravenous [IV] vs enteral) rather than other feeding modalities (diet, pattern) had contributed to the outcome.

We previously showed that parenteral nutrition (PN) compared with formula feeding results in hepatic insulin resistance and steatosis in neonatal pigs. The current aim was to test whether the route of feeding (intravenous [IV] vs enteral) rather than other feeding modalities (diet, pattern) had contributed to the outcome.

Three studies were conducted to measure the effect of plane of nutrition on visceral organ growth and metabolism. In study 1, rats fasted for 72 h generally had lower visceral organ mass, RNA content and ratios of RNA/DNA and protein/DNA than fed rats. In vitro oxygen consumption and valine incorporation rates expressed per unit of tissue did not differ between treatments. However, nutrient restriction decreased total liver oxygen consumption by decreasing organ and cell size. In study 2, lambs were fed ad libitum (ADLIB) or a maintenance (MAINT) diet for 21 d. During the 21-d period at 7-d intervals, four lambs per treatment were slaughtered and measurements of visceral organ size and metabolic activity obtained. During the 21-d period, ADLIB lambs had higher visceral organ mass, protein and RNA contents but lower DNA concentrations than MAINT lambs. Ratios of visceral organ RNA/DNA and protein/DNA in ADLIB lambs were higher than MAINT lambs. Estimates of in vitro oxygen consumption, valine incorporation and substrate oxidation per unit of tissue were relatively similar between treatments, however, estimates of total liver metabolic activity were higher in ADLIB than MAINT lambs. Plane of nutrition affected visceral organ size and metabolic activity through changes in cellular hypertrophy. The design, feeding regimen and duration of study 3 was identical to study 2, and blood flow and nutrient fluxes were measured in the liver and portal-drained viscera (PDV). During the 21-d period, ADLIB lambs had higher liver and PDV blood flow and oxygen consumption than MAINT lambs. In the control period, total splanchnic tissues (liver + PVD) represented an average of 52% of whole body oxygen consumption which increased to 69% in ADLIB lambs and decreased to 41% in MAINT lambs after 21 d. Net portal absorption of NH$\sb3$-N, $\alpha$-amino-N (AAN) and essential amino acids and hepatic uptake of AAN, essential and nonessential amino acids in ADLIB lambs was higher than MAINT l