[Nitrogen metabolism of broilers fed N-15 labeled wheat. 3. Blood, liver, spleen, thymus, kidney, brain, pancreas, labile N reservoir]

[Dynamics of amino acid and protein metabolism of laying hens after the administration of 15N-labeled wheat protein. 8. 15N-labeling of nitrogen and 15N incorporation into the amino acids of the liver]

Over 4 days 12 colostomized laying hens received, together with the ration, 36 g wheat with 14.37 atom-% 15N excess (15N'), The basic amino acids were nearly equally labelled. Three animals each were butchered after 12 h, 36 h, 60 h, and 108 h after the last 15N' application. Emission spectrometric determination of 15N' in the liver and in the amino acids was carried out. In addition, atom-% 15N' was determined in the free amino acids and the peptides. The labelling in the liver 12 h after the last 15N' application amounted to 1.75 atom-% 15N' and decreased after 108 h to 0.81 atom-% 15N'. The average TCA precipitable 15N' quota in the total 15N' amounted to 81.4% and was nearly identical at all measuring times. The arginine 15N' amount in the liver was twice as high as that of lysine 15N'. In dependence on the period of time after the last 15N' application the decrease in the labelling of the free arginine is considerable in comparison to free lysine. At the first measuring time (12 h) it was 1.69 atom-% 15N' and at the last one (108 h) 0.57 atom-% 15N'. Based on the results of 15N' labelling of the peptides in the liver further, more detailed series of experiments for studies of the peptide metabolism in the liver should be carried out.

[Evaluation of 15N marked urea in the laying hen. 4. Incorporation of 15N in blood, its fractions and follicles in various developmental stages]

In order to study the utilization of urea in poultry, 3 colostomized laying hybrids were orally supplied with a traditional ration supplemented with 1% 15N'-labelled urea with a 15N excess (15N') of 96.06 atom-% over a period of 6 days. After another 2 days on which the hens received the same ration with unlabelled urea, they were butchered. The atom-% 15N' of the blood on an average of the 3 hens was 0.64, of the plasma 1.40 and of the corpuscles 0.47. The TCA-soluble fraction of the blood had an average 15N' of 1.14 atom-%; the 15N amount is 9.7% of the total amount of 15N in the blood. The amount of 15N' in the urea in the blood was 6.8 atom-%. This shows that the absorbed urea is decomposed very slowly. The quota of 15N' in the basic amino acids from the total 15N' of the blood plasma is only 0.3% and that of the corpuscles 2.2%. The average 15N' of the mature follicles is 2.39 atom-% whereas the smallest and the remaining ovary contain 1.12 atom-%. The labelling level of lysine in mature egg cells was, in contrast to this, only 0.08 atom-% 15N' and in infantile follicles 0.04 atom-% 15N'. 1% of the 15N' quota is in the follicles and the remaining ovary. Of the basic amino acids, histidine is most strongly labelled. The as a whole lower incorporation of the 15N from urea into the basic amino acids shows that the nitrogen of this compound can be used for the synthesis of the essential amino acids to a low degree only.

[Effect of fasting on metabolism of free amino acids of various broiler tissues]

16 male broiler chicken fed with commercial-grade broiler fattening feed were killed in groups of four in intervals of 3, 6, 12 and 25 hours after the last food intake. The content of free amino acids was quantitatively determined in the small intestines, the liver and the complete muscular system. The highest concentration of free amino acids per gram of tissue could be detected in the small intestines between 3 and 6 hours and--phase shifted--in the liver between 6 and 12 hours after the last food intake. The changes of the concentration in the muscular system between the four measuring points were in most cases not statistically significant. The content of free amino acids in the three proofed tissues of fattening hybrids with a high demand of amino acids and a high protein synthesis performance was considerably above the values for rats as they are given in technical literature. The rhythmic changes of the concentration of free amino acids in the tissues in dependence on the interval between the last food intake and the killing require standardized conditions for metabolism-kinetic investigations of which the calculation of the content of free amino acids is part.

[Effect of fasting on N-metabolism of broilers]

Four male broilers each were killed 3, 6, 12 and 24 hours after the last food intake and divided into nine parts, The significant diminishing of the fresh liver mass in the test period amounted to 31%. With the increasing fasting time the N-content per g dry matter increased in liver, pancreas, muscles and the rest of the carcass. Because of the decrease in mass a statistically proved diminishing of the total N mass could be registered. The most significant changes were established in the total content of N soluble in TCA in the organs. The decrease in % from the first to the fourth measuring point amounted to 44% (liver), 40% (kidneys) and 28% (small intestines). Concerning these three organs we can maintain that the changes in the total N-content registered in the 24 hours fasting are chiefly limited to the TCA-soluble quota.

[Nitrogen metabolism of broilers fed 15-N labeled wheat. 4. 15-N concentration in muscles and nitrogen utilization]

Broilers were fed 15N labelled wheat and the concentration of the labelled isotope in muscular tissue was determined. A negative correlation was found to exist between the percentage proportion of N in the muscle fractions and the level of 15N frequency established 12 hrs after administration of the labelled ration. Higher rates of tracer incorporation were observed in the muscles of legs and other muscles (predominatly red muscles) than in pectoral muscles (white muscles). The heart was shown to exhibit the lowest N content and the highest level of 15N frequency of all muscle fractions. In view of the fact that some specific difficulties will arise when certain factors (trace elements, vitamins, ergotropic substances, genetic factors) which influence the N metabolism of fattening poultry, are estimated on the basis of the conventional N balance trials the present tracer technique is recommended for use as an alternative method in studies of the kind just described. In the present trial 20% of the wheat N were utilized for the production of meat N in muscular tissue.