PROTEIN-UTILIZATION DURING ENERGY UNDERNUTRITION IN SHEEP SUSTAINED BY INTRAGASTRIC INFUSION - EFFECT OF BODY FATNESS ON THE PROTEIN-METABOLISM OF ENERGY-RESTRICTED SHEEP
Sa. Chowdhury et al., PROTEIN-UTILIZATION DURING ENERGY UNDERNUTRITION IN SHEEP SUSTAINED BY INTRAGASTRIC INFUSION - EFFECT OF BODY FATNESS ON THE PROTEIN-METABOLISM OF ENERGY-RESTRICTED SHEEP, British Journal of Nutrition, 78(2), 1997, pp. 273-282
The effect of body fat content on the protein metabolism of energy-res
tricted sheep has been studied in two experiments, In the first experi
ment, six Suffolk-cross wether sheep, three weighing about 39 kg and t
hree of about 61 kg, were given, progressively increasing amounts of c
asein-N from 0 to 3000 mg N/kg metabolic body weight (W-0.75) daily wi
th constant energy, 91 kJ/kg W-0.75 daily, from a high-propionic acid
mixture of volatile fatty acids (VFA). In the second experiment, two l
ean and two fat sheep of similar body weights were given progressively
increasing amounts of casein with the same VFA mixture. All the anima
ls attained a positive N balance when they were in negative energy bal
ance, N balance was not affected by body fatness of the magnitude stud
ied, although lean animals utilized increasing levels of standard VFA
(acetate-propionate-butyrate 65:25:10, molar proportions) infusion for
N accretion more efficiently than fat animals, Endogenous energy was
utilized for protein accretion with an efficiency of 0.56, Supply of g
lucogenic VPA equivalent to 28 mmol glucose/kg W-0.75 reduced fasting
N excretion by 39 %, Easting heat production decreased from 335 to 300
kJ/kg W-0.75 with the infusion of casein and glucogenic VFA. It is ar
gued that fasting induces additional heat losses due to raised protein
metabolism and is unsuited as a baseline for dietary assessment.