[Studies with 15N-labeled lysine in colostomized hens. 1. 15N excretion in urine]

[Methodological aspects of the determination of nitrogen metabolism parameters from 15N-tracer experiments on swine based on nitrogen metabolism models. 2. Calculation of N metabolism parameters from the time of urinary excretion of 15N]

After a 45-hour infusion of 15N-lysine and 15N-glycine resp. with pigs of 25 kg live weight, the infusion of the tracer was disrupted and a 3-day reduction phase was made part of the experiment. The N-metabolism parameters such as protein synthesis and decomposition quotas were calculated on the basis of the temporal development of 15N-amounts excreted in urine. The labelling and reduction phases were evaluated simultaneously. By means of including the total N-amount of the animal body the balance calculation becomes more stable. The possible influence of the tracer amino acid in connection with the 3-pool-model is discussed on the basis of the ascertained parameters.

[Studies of 15N-labeled lysine in colostomized laying hens. 6. 15N incorporation into basic amino acids of the liver, kidney, meat, bones and remaining body as well as 15N balance]

Three colostomised laying hybrids received 91.40 mg L-lysine-15N-excess (15N') each over a period of four days in a metabolism experiment with 15N-labelled lysine. After another four days, during which the hens received the same rations supplemented by commercial L-lysine, the animals were butchered and divided into individual fractions. After the hydrochloric hydrolysis of the organs and tissues the heavy nitrogen of lysine, histidine and arginine were separated, quantitatively evaluated, processed and measured with an emission spectrometer. Atom-% 15N' on an average amounted to 0.20 in the liver, 0.16 in the kidneys, 0.06 in the meat and 0.05 in the bones. Of the rediscovered 15N' applied, faeces contained 8.1%, urine 18.3%, the eggs 24.3%, the blood 4.9%, the meat 20.5%, the bones 5.2%, the gastro-intestinal tract with its contents 4.5%, the liver 3.5%, the kidneys 0.9%, the reproductive organs 3.7% and the rest 6.1%. The quota of rediscovery of the 15N' applied was 95.7%. 62% of the total 15N' was rediscovered in eggs, body and faeces as lysine 15N'. There was significantly more 15N' in the arginine in all fractions than in the histidine. The quota of the lysine-15N' of the total 15N' differed considerably in the fractions: less than 40% bones and blood; 48...56% gastro-intestinal tract, faeces, oviduct, kidneys; 62...63% remaining ovary, rest; 69...71% eggs, meat, liver. It could be proved that the alpha-amino group of lysine is to a large extent incorporated into other amino acids. Further proof that the amino acid metabolism proceeds in two phases was submitted, i.e. hight amounts of amino acids previously deposited in the body are used for egg synthesis.

[15N-labeled lysine in colostomized laying hens. 5. 15N incorporation into blood fractions and the gastrointestinal tract]

In the metabolism experiment three colostomized laying hens received, together with a commercial ration of 120 g, 0,2% 15N-labelled L-lysine with an atom-% 15N-excess (15N') of 48%; subsequently the same ration was fed over a period of 4 days with 0.2% unlabelled L-lysine. After the end of the experiment the hens were slaughtered. The atom-% 15N' was determined in total, in the lysine, histidine and arginine N in the corpuscles, the plasma, the NPN-fraction of the blood in the stomachs, the small intestine, the caecum and the rectum. 15N' in the corpuscles was 0.11 atom-%, in the blood plasma 0.17 atom-%, in the NPN-fraction of the blood 0.09 atom-%, in the tissue of the gastro-intestinal tract 0.11 atom-% and in its contents 0,12 atom-%. On average the blood contained per hen 77.9% lysine-15N', 16.4% arginine-15N' and 5.7% histidine-15N' of the basic amino acid-15N'. For the gastro-intestinal tract 78.7% lysine-15N', 19.0% arginine-15N' and 2.3% histidine-15N' of the 15N' of the basic amino acids were ascertained. In comparison to histidine the alpha-amino-N of lysine is incorporated to a considerably higher degree into arginine. For lysine and arginine the atom-% 15N' in the contents of the gastro-intestinal tract for days after the end of the supplementation of labelled lysine is between 8 and 10 times higher than in the feces of the last day of the experiment. This indicates a considerable secretion of the two amino acids in the gastro-intestinal tract and their re-absorption to a large extent.

[15N-labelled lysine in colostomized laying hens. 4. Incorporation of 15N-lysine into various amino acids of egg yolk and white]

Each of three colostomized laying hens received per os 0.2% L-Lysine with 48 atom-% 15N-excess (15N') labelled in alpha-position in addition to a pelleted laying hen ration of 120 g over a period of 4 days. On the following 4 days they received equal amounts of unlabelled lysine. The eggs laid during the 8 days of the experiment were separated into the white of egg, the yolk and the eggshell, and the to and heavy nitrogen in the individual fractions were determined. Above that, 17 amino acids and their atom-%15N' were determined in the 19 samples of the white and yolk of egg. Of the total 15N' from the lysine fed in the 4 days, 10.1% were found in the yolk, 10.5% in the white of egg and 1.1% in the eggshells of the eggs laid during the 8 days of the experiment. 85% of the total amino acid-15N' of the yolk and 86% of the white of egg detected to be lysine-15N'. The 15N'-amount of the other 16 amino acids was mainly concentrated in the two acid and basic amino acids. Approximately 50% of the non-lysine 15N' in the egg are contained in aspartic acid, glutamic acid, histidine and arginine. A very low incorporation of the labelled lysine only could be detected in the aromatic and sulphur-containing amino acids from both the yolk and the white of egg. 43% of the 15N' was detected in the 10 essential and semi-essential (except lysine) and 57% in the 6 non-essential amino acids of the yolk and 52% and 48% resp. of the white of egg. One can summarize that the incorporation of 15N' into the egg shows the same development as that of the labelled amino acids of the wheat protein and that 15% of the lysine-15N' could be detected in the 16 other amino acids.

[Studies of 15N-labeled lysine in colostomized laying hens. 3. 15N incorporation into the amino acids of the follicle, residual ovary and oviduct]

In a metabolism experiments with 15N-labelled lysine 3 colostomized laying hybrids received over 4 days 0.2% L-Lysine with 48 atom-% 15N-excess (15N') in addition to a ration conventionally produced and, subsequent to this, unlabelled lysine for four days. At the end of the experiment the hens were butchered: individual organs and tissues were prepared for 15N-analysis. The incorporation of the lysine-15N' into the further amino acids in the follicles, the ovary and the oviduct is described. The atom-% 15N' of the complete range of amino acids was analysed in the individual follicles. Various levels of heavy nitrogen could be detected in all essential and non-essential amino acids. Of the total amount of 15N' detected in the follicles 64.0% 65.0% and 61.2% resp. could be detected in lysine and 25.2%, 25.4%, 28.7% resp. in the other amino acids (hens 1 to 3). In the ovary on average 61.6% and on the oviduct 54.2% of the respective 15N'-amount was detected in lysine. In the ovary 10.9% and in the oviduct 8.4% 15N' of the total 15N' of these samples were incorporated into the arginine molecules.

[Studies with 15N-labeled lysine in colostomized hens. 2. 15N excretion in feces]

Over a period of four days colostomised hens were given 15N-lysine, and the development of 15N-excretion both in the TCA-soluble and the TCA-precipitable fraction of the faeces was measured over eight days. In both fractions the total, lysine, histidine and arginine N and 15N-excess (15N') was determined. The average apparent digestibility of 14N was 81.2% +/- 1.1% and of 15N' 93.2% +/- 0.7%. Labelled N is already excreted in faeces 3 hours after its application. The TCA-precipitable N is less strongly labelled than the TCA-soluble N. During the application of 15N' the labelling in faecal lysine is nearly one power of ten higher than in total N. The atom-% 15N' of the lysine could also be distinctly detected in arginine and histidine. The quotas of the total 15N' in faeces were 3.5% for arginine-15N' and 0.8% for histidine 15N'; 15N' can mainly be detected in the soluble fraction.