PROTEIN-UTILIZATION DURING ENERGY UNDERNUTRITION IN SHEEP SUSTAINED BY INTRAGASTRIC INFUSION - EFFECTS OF PROTEIN INFUSION LEVEL, WITH OR WITHOUT SUB-MAINTENANCE AMOUNTS OF ENERGY FROM VOLATILE FATTY-ACIDS, ONENERGY AND PROTEIN-METABOLISM

Utilization of endogenous and exogenous energy for protein accretion d uring energy undernutrition has been studied, Nine lambs nourished by intragastric infusion were given either progressively increasing or de creasing amounts of casein-N up to 2550 mg/kg metabolic weight (W-0.75 ), With Or without 250 kT/kg W-0.75 of volatile fatty acids daily, Ene rgy balance (respiration calorimetry) and N balance were measured, Whi le all experimental animals were in negative energy balance, N balance increased curve-linearly with the increase in casein-N infusion and a ttained positive N balance, Endogenous energy (presumably body fat) wa s found to meet the energy needs for protein accretion during energy u ndernutrition, It is concluded that body fat can be effectively utiliz ed to support lean-tissue growth during energy undernutrition, so that the classical nutritional concept of dietary energy:protein ratio is only meaningful when both endogenous and exogenous energy are consider ed.