Biomedical subjects
Publications and source records attributed to H Bergner.
For several reasons the utilisation of 15N for the characterisation of the microbial protein synthesis in the artificial rumen seems to be, in contrast to the incorporation of 35S, not very suitable in order to characterise the feed value of straw materials.
Chymostatin is an effective inhibitor of intracellular proteinases in vitro. In the present experiment male rats were injected intraperitonealy during a 3 days period twice daily with a solution containing 0,9 mg Chymostatin per 100 g live weight. Reference animals received a control injection containing the same solvents but no chymostatin. During this period a daily nitrogen balance was made and metabolic faecal nitrogen and true digestibility of nitrogen were estimated using 15N-labelled animals. Furthermore, apparent biological half lives of proteins in liver and intestinal tissues were determined following the decay curves for radioactivity in proteins 48 hours after injection of L-[5-3H]-arginine und L-[guanido-14C]-arginine. The fractional rate of protein synthesis in tissues was measured by a 6 hours continuous infusion technique with L-[U-14C]-tyrosine and L-[U-14C]-leucine. Among the parameters estimated only the apparent biological half lives of proteins in liver and intestinal tissues were influenced by chymostatin. However, the prolonged half lives seemed to be rather an effect of an increased reutilisation of amino acids resulting from the intracellular protein breakdown than a decreased rate of protein degradation. The in vivo effect of the proteinase inhibitor was by far inferior compared with the action in vitro. Factors like distribution, degradation and excretion of the inhibitor could be responsible for the moderate in vivo action of chymostatin.
After 15N-labelling over 7 days male albino rats (92-95 g live weight) received either a wheat or whole egg diet (10 animals each) for 4 days. On the following day of the experiment 5 animals each continued to receive their diets as their morning meal (group 1 whole egg, group 3 wheat) and 5 animals each after the previous feeding of a wheat diet received a 2.9 g whole egg diet (group 2) and after the previous feeding of a whole egg diet a 2.85 g wheat diet (group 4) resp. This morning meal was supplemented with chromium(III)oxide. The rats consumed their meals within 20 minutes. The animals were killed 3.5 hours after the beginning of feed intake. At that time the following relative amounts (in % of the intake) could be detected in the stomach in the sequence of groups 1 to 4: Cr2O3 = 22.5; 26.5; 57.5 and 64.2; dry matter = 25.4; 22.1; 43.2 and 38.5. The better agreement between the whole egg diet and Cr2O3 can be explained with the hydrophobic qualities of Cr2O3 and the small disposition of the Cr2O3 to decompose in combination with the whole egg diet. In the first third of the small intestines less than 1% of the intake of Cr2O3 and a maximum of 3.5% of the DM could be detected. Between 20 and 36% of the Cr2O3 and between 15 and 20% of the dry matter intake were ascertained in the small intestines as a whole; in the large intestines the values were 12-20% of the Cr2O3 and 16-23% of the DM. Endogenous 15N-secretion could be ascertained in all parts of the digestive tract. According to the method suggested by U. Bergner and H. Bergner (1982), protein digestibility in the last third of the small intestines was calculated as follows: (formula; see text) The following ileal digestibility values were calculated for crude protein: whole egg = 95.6%; whole egg (wheat previously) = 95.5%; wheat = 94.1%; wheat (whole egg previously) = 85.1%. It is a precondition for the application of this method that at the time of killing representative quotas of the diet sample to be tested can be detected both in the stomach and the large intestine so that the decrease of 15N-labelling in the ileum is actually caused by the test protein.
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Four 40 kg castrated male pigs fitted with simple 'T' cannulas in the terminal ileum were given diets of varying crude fibre content in a change-over experiment with two periods. The basal diet was composed of wheat and fishmeal supplemented with minerals and vitamins. To this was added varying levels of partially hydrolysed straw meal to give crude fibre contents ranging from 40 to 132 g/kg. After adaptation to the particular levels of straw meal, faeces and ileal digesta were collected during successive 24 h periods. Nutrient digestibility values were determined by the chromic oxide ratio method. The addition of treated straw meal to the diet had little or no influence on the DM content of digesta or faeces. The excretion of N in faeces increased with increasing fibre intake but there was no effect on urine N excretion. The overall apparent digestibility of N was reduced from 89 to 79% as crude fibre intake increased from 40 to 132 g/kg but ileal apparent digestibility of N remained constant at about 68%, suggesting that the effect was mediated through hindgut bacteria. Increased fibre intake caused increased net secretion of Na in the small intestine and reduced the apparent absorption of P in the large intestine.
In studies with 16 breeding sows of the country species the feed value of straw materials and their fitness for use were ascertained in a long-term experiment. On the feeding basis of a concentrate ration (IV) untreated (I), HCl treated (II = HCl treatment without steaming) and partly hydrolysed straw meal (III = HCl treatment with subsequent steaming) were tested. In the course of the experiment and at a nutrient level of 1 (maintenance requirement), the digestibility of the organic matter of the ration and that of some major and trace elements, N and mineral balances as well as feed passage rate and water excretion in faeces were ascertained at selected measuring times. The following mean results were achieved: The integration of all straw materials tested lead to a significant reduction of the digestibility of the organic matter of the total ration, the least negative effect was caused by partly hydrolysed straw meal (III). The fractions crude protein, crude fibre and N-free extracts were mainly affected. Straw meal integration had a gravidity-conditioned influence on the daily N balance. Increased N excretion in faeces could only be compensated by non-pregnant animals by a decreased N excretion in urine. The mineral balance (Ca, P, Na, Cu and Mn) remained largely uninfluenced by the straw supplement. The feed passage rate was reduced by the use of all straw meal variants to ca. 50% of the value measured after the sole feeding of concentrate (IV). Feed passage rate and water excretion in faeces were approximately reciprocal. The digestibility of the organic matter of the straw materials ascertained according to the difference method amounted to 7.4 (I), 18.1 (II) and 27.9% (III); that of the N-free extracts in the same sequence to 10.0, 22.0 and 34.9%. The calculated energetic feed value was for I = 70.7, for II = 154.9 and for III = 240.7 EFUpig/kg DM.
N intake in the form of protein has neither got an upper nor a lower limit for agricultural working animals within a diet and there is no control mechanism for it. A high surplus of certain amino acids results in a reduction of feed intake. N excretion in faeces depends on 1) the excretion of N containing indigestible feedstuffs, 2) bacterial nitrogen synthesis in the large intestine and 3) the excretion of true endogenous N containing substances (digestion enzymes, intestinal epithelium, N containing endogenous secretion). There are no other control mechanisms for N excretion in faeces. N excretion in urine mainly comprises the nitrogen from the degeneration of amino acids and nucleic acids. The interrelations between urea, NH3, allantoin, creatine and creatinine, uric acid and hippuric acid depend on the species (monogastric or ruminants), on the nitrogen and N amount consumed and on the recycling ratio of the amino acids. The absolute amount of N excretion is not subject to any control mechanism, it depends on the intake of protein and NPN substances, the interim stages, however, which lead to the formation of excretory products, are intermediately controlled. The most important interim stage is protein biosynthesis, which is a fixed, intermediately controlled value in maintenance level. Under growth conditions only, the protein synthesis quota can exceed the protein degradation quota of the total organism (positive N balance). The control mechanisms of protein biosynthesis have, according to current knowledge, the following structure: Stimulation: 1) growth hormone (STH) stimulates protein synthesis by means of somatomedins; 2) hormones of the thyroid gland (T4 and T3) are controlled by the hormone stimulating the thyroid gland (TSH); 3) insulin. Inhibition: 1) somatostatin inhibits STH, TSH and insulin; 2) cortisol directly inhibits protein synthesis and stimulates protein degradation. The control mechanisms of protein turnover in addition to genetic coding and proteolysis extend in the framework of evolution over the period of 3,400 million years from the existence of the bacterial cell to the development of mammals, which is 74% of the age of the earth and approximately 90% since the existence of the first traces of life. The control mechanisms of protein turnover in mammals do not permit gene manipulation in protein synthesis as in bacterial cells since the control mechanisms mentioned are missing there.
A digestibility experiment was carried out under conditions of reduced water supply (1/3 in comparison to the control group) and feed supply ad libitum or on maintenance level with 5 wethers of an average body weight of 43.2 kg. They were fed with alfalfa pellets with a Na supplement in the form of NaH2PO4. The water restriction increases the apparent digestibility of the nutrients (except crude fat), significantly so, however, only in the group fed ad libitum as a result of the lower digestibility in ad libitum feed intake. In the group with water restriction the absolute amount of digested nutrients is diminished, however, and in group Ib (feed supply on maintenance level) falls clearly below maintenance requirements. In a comparison of the values of apparent digestibility of the nutrients acquired by various methods (traditional method and indicator method - HCl insoluble remaining ash) the latter method is more susceptible to error. This method is, however, considerably easier in its execution. In comparison to ad libitum water supply the mean retention time of the feed increases due to restricted water supply. The decreased feed intake seems to have a bigger influence on the mean retention time of the marker than water restriction.
Six heifers with a live weight of 215, 227 and 238 kg (experiment 1) and 220, 227 and 233 kg, resp. (experiment 2), were supplied with ileocaecal re-entrance cannulae, jugular venous catheters and bladder catheters. The ration consisted of 4 kg maize silage and 4 kg wheat straw pellets per animal per day. Up to 3.5 kg of the straw pellets, consisting of 73% wheat straw, 10% barley, 12% molasses, NPN salts and a mineral mixture, were consumed per animal per day. In a preliminary period 50% of the digesta flow was collected over 12 h/d on 5 consecutive days and stored in a deep-freeze. During the main trial the re-entrance cannula was disrupted and the flowing digesta were quantitatively collected at the end of the ileum; previously collected digesta were supplemented with 15N urea and every hour over 24 h infused into the caecal part of the re-entrance cannula. Between the 24th and 30th hours the digesta were infused without 15N urea supplement. In trial 2 the digesta were also supplemented with partly hydrolysed straw meal between the 1st and 30th hours (approximately 10% straw meal DM related to digesta DM). There were no differences between trials 1 and 2 with regard to the increase of atom-% 15N excess (15N') in the plasma urea. The 15N labelling decrease of the plasma urea N shows that the half-life is 7.9 h in trial 1 and 7.0 h in trial 2. The NH3 nitrogen in faeces was distinctly higher labelled in trial 2 after the supplement of straw meal than in trial 1. The total N in faeces was also twice as highly labelled as in trial 1. Atom-% 15N' in urine was significantly higher in trial 2 than in trial 1 between the 6th and 16th hours after the beginning of 15N urea supplementation. In the decrease curve of atom-% 15N' (after the 26th hour of trial) the values in trial 1 were generally higher than in trial 2. The higher bacterial protein synthesis in the large intestine in trial 2 (after the supplement of partly hydrolysed straw meal) had the effect that 13.6% of the supplemented 15N' was excreted in faeces by the 30th hour of trial, in contrast to this only 4.7% in group 1. Up to the 4th day after the 15N urea infusion these values increased to 16.2 and 6.1%, resp., only.
Wethers of an average live weight of 43.2 kg received alfalfa pellets either according to maintenance requirement (1.3 kg = group I) or ad libitum (1.5 times the amount; 2.0 kg = group II). In variant a both groups received water ad libitum, in variant b the animals received 1/3 of the amount of water, which was taken in ad libitum. Apparent digestibility was between 59 and 64%, the lower value of which was ascertained with the higher feed intake in variant a. 85% of the apparently digested nitrogen were excreted in urine after optimal water supply and ca. 100% after reduced water supply, so that a slightly negative N balance (Ib) and an N balance of +2.3% res (IIb) were achieved. The N balances amounted to +9.4% (Ia) and +8.4% (IIa) resp. after sufficient water supply. The water intake in liters/kg consumed DM reached the following values (in brackets total water intake from drinking water + water in the feed): Ia = 3.16 (3.30), Ib = 1.38 (1.52), IIa = 2.94 (3.08) and IIb = 1.58 (1.72). The water balance (in % of the total water intake) reached the following values in the same sequence: 13.7, 13.2, 17.2 and 25.3. The water content of the body (according to the phenazone dilution method determined from one sheep each) decreased in Ib by 4.7% and in IIb by 5.7% and thus did not reach critical limits. The quota of urea N in urine significantly increased after water restriction. Urea concentration and haematocrit in the blood plasma did not show any significant changes in dependence on water intake; the same was ascertained for the molar quotas of volatile fatty acids in the rumen fluid and in faeces.
Three bulls with an average live weight of 228 kg were fitted with ileo-caecal reentrant cannulas for the experiment. The rations were composed of 3 kg maize silage and 3 kg wheat straw pellets per animal and day. In a previous period 50% of the digesta was collected over 12 hours and stored deep-frozen. In the main period the digesta flow was interrupted for 30 hours. The digesta flow was collected quantitatively. In the caecal part of the re-entrant cannula previously collected digesta and starch (over 30 hours) as well as 15N urea (over 24 hours) were supplemented. The amount of starch corresponded to about 10% of the DM of the digesta. Analyses of the urine, faeces, ileum digesta and blood plasma were carried out. The quota of starch clearly stimulates bacterial processing in the large intestine so that 20.5% of the supplemented 15N was excreted in faeces within 24 hours. 91.2% of the 15N in the faeces was localised in the bacteria fraction. Individual differences of the animals distinctly show the connection between the excretion of the 15N in faeces and urine. A decreased isotope excretion in faeces of 17.2% for animal 3 in contrast to the 23% for animals 1 and 2 showed an increased elimination of the 15N through the kidney with 32.7% instead of 25.2%. The largest proportion of the ileum digesta, i.e. 46%, can be localised in the 15N urea fraction; the NH3-fraction is also distinctly labelled. With time progressing, the 15N quota flowing from the rumen to the small intestine increases.