G. Gebhardt

Methodische Untersuchungen zur Bestimmung der Verdaulichkeit des Rohproteins beim Hühnergeflügel

A comparison of various methods for the determination of the digestibility of crude protein in chickens was made. The chemical methods of dividing faeces and urine according to HARTFIEL and EKMAN were tried out, and a new method based on the determination of alpha-NH2-N was developed and tested. Colostomy of hens served as the basis of the comparison for the correctness of the chemical methods. The best approximation to the digestibility quotient of the crude protein according to colostomy was achieved with the alpha-NH2-N-method, which can to a large extent be well automated and can do without N-determination. Faeces-urine-N-separation according to EKMAN also resulted in a good approximation to the values according to colostomy.

Ernährungsphysiologische Untersuchungen an Schweinen zur Beurteilung von modifizierten Proteinen

Modified proteins were tested in absorption investigations with eight pigs with ileocaecal re-entrant cannulae. The apparent digestibility up to the end of the small intestines showed considerable differences between the feed proteins (77-93%). The same differences could be observed with regard to the apparent absorption of amino acids. Concerning the true N-digestibility resp. the true absorption of the amino acids in the above mentioned section of the intestinal tract there were hardly any differences between the proteins given. The results show that there is a relation between the amount of endogenous N in the chyme at the end of the small intestines and the protein consumed. The amount of endogenous N in the chyme in the small intestines influence N-excretion in urine and thus the intermediary utilisation of feed protein. From the point of view of nutrition physiology it follows that the spun vicia-faba protein/casein (1 : 1) fibres (C) approximate best the value of casein (A). While the treatment of this mixed protein with dyaldehyde starch had a negligible effect on the ascertained parameters only, the treatment of the same protein with aluminium chloride diminished its value more. The isolated vicia-faba (B) was the poorest of the modified proteins tested.: Modified proteins were tested in absorption investigations with eight pigs with ileocaecal re-entrant cannulae. The apparent digestibility up to the end of the small intestines showed considerable differences between the feed proteins (77-93%). The same differences could be observed with regard to the apparent absorption of amino acids. Concerning the true N-digestibility resp. the true absorption of the amino acids in the above mentioned section of the intestinal tract there were hardly any differences between the proteins given. The results show that there is a relation between the amount of endogenous N in the chyme at the end of the small intestines and the protein consumed. The amount of endogenous N in the chyme in the small intestines influence N-excretion in urine and thus the intermediary utilisation of feed protein. From the point of view of nutrition physiology it follows that the spun vicia-faba protein/casein (1 : 1) fibres (C) approximate best the value of casein (A). While the treatment of this mixed protein with dyaldehyde starch had a negligible effect on the ascertained parameters only, the treatment of the same protein with aluminium chloride diminished its value more. The isolated vicia-faba (B) was the poorest of the modified proteins tested.

Untersuchungen zur Bestimmung der endogenen N-Sekretion im Dünndarm bei Schweinen

The method of isotope dilution for the determination of endogenous N-secretion was used with three pigs of a live weight of between 15 and 27 kg, which were provided with simple cannulae at the end of the small intestines. The test animals received a single dose of a semi-synthetic ration with 15N-labelled dried curds as sole source of protein. The passage rate to the ileum ascertained with the help of 51Cr2O3 was 70% in 24 hours. During the test period of 24 hours the endogeneous N-amount in the ileum chyme was 1.11 g resp. 56.6 mg/kg live weight. Of that, 60% were allowed to be absorbed in the chyme at the end of the small intestine.

Untersuchungen zum Zusammenhang zwischen Proteinqualität, Höhe der Proteingabe und endogener N-Ausscheidung

The influence of various protein qualities as well as of different levels of protein on the amount of endogenous N-excretion, metabolic fecal nitrogen (MFN) and endogenous urinary N (EUN) was determined at growing albino rats. The test rations were labelled with admixtures of 15N-DL-methionine resp. 15N-DL-lysine or contained feed protein enriched with 15N. EUN and MFN and their sum (the N maintenance requirement) showed the influence of the respective protein source and its dependence on the protein level. The endogenous N-excretions showed an opposite tendency to the N-balance; for high-quality protein feedstuffs with a high N-balance (e.g. dried eggs) they are lower than for protein source of inferior quality, with a low N-balance only (e.g. wheat gluten). Presumably this interaction of retention and maintenance is due to the complementary effect of exogenous and endogenous amino acids in the N-resp. amino acid-pool. Provided that the N-dose and the liver weight of the animals are comparable, the N-balance appears to be more suitable as parameter for the description of the protein quality and the calculation of the protein utilisation than N-retention, as the sum of N-balance and the values of MFN and EUN (depending on the feedstuffs and the N-level).

[N-metabolism as modelled by metabolism of 15N-labelled wheat in rat experiment].

Male albino rats of a weight of 90 g received a test ration with 15N-labelled wheat as protein source over a period of 1 to 8 days. The 15N-excess in urine, feces, some organs, the remaining carcass and in the blood was determined in dependence on time. On the basis of two different pool models the N-metabolism values could be calculated. Protein synthesis and disintegration rates calculated by means of the N- and 15N-balances of the pool in the steady state of the pool labelling amounted to 252.9 mg N per day resp 203.0 mg N per day. The calculation based on the time-dependent curve of the daily 15N-excretion in urine resulted in corresponding synthesis and disintegration rates of 197.0 mg N per day and 134.6 mg N per day. Labelling curve and results are discussed.

Untersuchungen zur Stickstoff- und Aminosäurenresorption beim Schwein

The seeming and the actual absorption of amino acids of three pigs with a body mass of 50 kg was determined by inserting re-entrant cannulas at the upper small intestine and its end. The test ration contained dry curds labelled with 15N. The content of N and of amino acids as well as the 15N-excess in the amino acids were determined in the food and the chyme. This served the ascertainment of the actual absorption of amino acids in the small intestines.

Untersuchungen zum N-Umsatz Wachsender Schweine unter Besonderer Beachtung der Lysinwirksamkeit Unterschiedlicher Lysinquellen

The results of measurings of N-metabolism in relation to the utilisation of the limiting amino acids are discussed on the basis of N-balance experiments with 20 growing female pigs (live weight 35-40 kg) with lysine-limited, highly digestible synthetic feed mixtures. Based on an N-utilisation model (Gebhardt, 1963), conclusions are drawn concerning the effectivity of lysine from various lysine sources. In accordance with literature, differences between synthetic lysine and microbial lysine concentrate could not be observed.

Ermittlung von N-Stoffwechselparametern im N-Steigerungsversuch an der Ratte unter Verwendung von 15N-Tracern

3 groups of 8 Wistar rats each of a live weight of ca. 215 g received graded N supplements. A number of N metabolism parameters were ascertained and discussed. Among other things, the protein synthesis and degradation quotas were ascertained by means of the 15N tracer technique. For the assessment a 3-pool model was used, the content of which was in so far extended as growth and metabolic faecal nitrogen are concretely taken into consideration. A quasi-continuous method of supplementing the tracer was chosen; it was discontinued in approximately the middle of the experiment. Thus the labelling and abatement phases in urine could at the same time be included in the calculation. The protein synthesis quota increases with N intake. It can be concluded from the course of the graph that it gravitates towards a saturation value.

Untersuchungen zum Zusammenhang Zwischen Kreatininausscheidung im Harn und der Qualität des Nahrungsproteins bei Wachsenden Schweinen

N-balance experiments, in which creatinine excretion in urine was measured, were carried out with 80 female fattening pigs. 16 protein sources of different quality were used. In addition to that, an N-increase experiment--protein quality remaining the same--and N-free experiment and results from literature were included into the assessment. The b-value (Gebhardt, 1963) served as the criterion for protein quality. The creatinine coefficient (mg creatinine in urine per kg live weight and day) could be determined as 40.2. There was a direct relation between the N-balance value and creatinine excretion, not however, in the N-increase experiment. Significant relations to the protein quality (b-value, Gebhardt, 1963) could only be established when N-excretion in urine was included.

Untersuchungen zur Eiweißverwertung von lysinergänztem Gerstenprotein und zur Wirkungsmöglichkeit der limitierenden Aminosäure Lysin an wachsenden Schweinen

In 57 N-balance experiments with castrated male pigs (20 ... 65 kg live weight) the influence of graded lysine supplements to crushed barley enriched with energy, minerals and vitamins on nitrogen metabolism and lysine effectiveness was tested. Close correlative relations between lysine concentration and the b-value, the NPU-value, N-balance and N-excretion in urine could be detected. In agreement with the law of minimum a constant lysine effectiveness could be observed within the limiting range. The supplemented synthetic lysine distinguished itself by the same effectiveness as the protein-bound barley lysine. When barley supplemented with lysine is used, an amount of lysine supplement should be chosen from the point of view of nutrition physiology which raises the total lysine content to a maximum level of 6.3 g/16 g N because lysine supplementation exceeding this value without the simultaneous supplementation of limiting threonine remains ineffective.