Protein turnover in growing pigs. Effects of age and food intake.
1. Measurements were made of the nitrogen and energy balances of pigs of 30, 60 and 90 kg given a conventional diet at various daily rates. 2. Body protein synthesis was estimated from the irreversible loss of leucine from the blood following the infusion of [1-14C]leucine, and from the oxidation of the labelled amino acid. 3. Protein synthesis (g/d) increased by 2.17 for each  1 g increase in daily protein accretion and by 1.55 for each 1 g increase in daily protein intake. 4. At 30 kg, pigs close to energy equilibrium synthesized 270 g protein daily compared with 406 g and 512 g when their ration supplied twice and three times their maintenance requirement. 5. There was a close correlation between the daily urinary excretion of urea + ammonia and total amino acid catabolism estimated from the catabolism of leucine, but the latter underestimated the observed excretion by 2.5 g N/d. 6. The results imply that protein turnover accounts for only a proportion of the heat production associated with protein deposition.
D000375:Aging; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001833:Body Temperature Regulation; D001835:Body Weight; D004032:Diet; D004044:Dietary Proteins / Q000378:metabolism; D004734:Energy Metabolism; D005260:Female; D007930:Leucine / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*; D013552:Swine / Q000378:metabolism*
D004044:Dietary Proteins; D011506:Proteins; D007930:Leucine; D009584:Nitrogen