Methodical aspects in the determination of metabolic N parameters in pigs using 15N as tracer and based on models of N metabolism. 1

One female pig each of approximately 25 kg live weight was labelled with 15N-glycine and 15N-lysine, resp., over a period of 45 hours by means of continuous infusion. The same unlabelled amino acid solutions were infused for another 72 hours. The main part of the energy was supplied orally. The temporal development of 15N labelling in the blood fractions and in urine as well as differential N excretion in urine were determined at short intervals. There were periodic deviations in the N metabolism, probably determined by habitual metabolic rhythms. The qualitative development of 15N excretion in urine was the same for both animals. If the utilisation of the infusion mixture was high and approximately equal, the animal labelled with glycine excreted - due to the specifics of the amino acid metabolism - more 15N than the one labelled with lysine. (author)