ADAPTATION OF ENERGY-METABOLISM TO UNDERNUTRITION IN EWES - CONTRIBUTION OF PORTAL-DRAINED VISCERA, LIVER AND HINDQUARTERS

Adaptation of energy metabolism to undernutrition and to the duration of undernutrition was studied in adult, non-pregnant, non-lactating ew es at the whole-animal, portal-drained viscera, liver and hindquarters levels. Arterio-venous and indirect calorimetry techniques were used. Animals were successively fed at 1 times (3 weeks) and at 0.5 times ( 7 weeks) their metabolizable energy requirements for maintenance (MEm) . Portal, hepatic and hindquarters blood flows in quietly standing ewe s decreased by 22, 19 and 11% respectively within the first week of un dernutrition and remained at that level thereafter. Standardizing hind quarters blood flow to that in a given posture (quietly standing) redu ced blood flow by 9.8%. In the portal-drained viscera and liver, O-2 e xtraction rates decreased, leading to 34 and 38% drops in O-2 consumpt ion with underfeeding respectively. In the hindquarters, O-2 extractio n rate increased, partly counterbalancing the drop in blood flow. Thus O-2 consumption of hindquarters tended to decrease but the effect was not significant. All changes appeared to be completed from day 5 of u nderfeeding. Consequently, the portal-drained viscera, liver and carca ss were responsible for 39, 32 and 5% respectively of the drop in,whol e-animal O-2 consumption with underfeeding. At the end of the 0.5 x ME m period, in vivo metabolic rates averaged 1.65, 4.89 and 0.38 mmol O- 2 consumed/d per g fresh weight of adipose-tissue-free portal-drained viscera, liver and boneless hindquarters respectively. Undernutrition imposed a much greater nutritional challenge to splanchnic tissues tha n to hindquarters. The former reduced their energy expenditure whereas hindquarters metabolism adapted by counteracting the slight drop in n utrient supply.