Research note: investigation on the metabolism of glycerol in the rumen of bulls.

Two bulls, each fitted with rumen and duodenal cannulas, received (in addition to a hay-grain diet) twice daily an infusion of 200 g glycerol into the rumen over a period of six days. During this preliminary in vivo investigation, the influence of a glycerol application on the rumen environment over a six-day adaptation period was examined. Samples of rumen fluid were collected daily, two hours after glycerol infusion. An additional 15N-urea application into the rumen was given on days 1 (without glycerol infusion), 3 and 7 (with glycerol infusion). Extra samples of rumen fluid and blood plasma (from puncture of vena jungularis) were taken through the 12th hour following urea application. Rumen fluid pH was reduced due to glycerol intake from 6.3 (day 1, without glycerol) to 5.4 by day 7. Molar proportion of acetic acid to propionic acid decreased from 3.5 (day 1) to 2.1 (days 6 and 7). Average glycerol disappearance rate from the rumen was 4.7 gl-1 h-1 for the first hour. Only small amounts of glycerol could be detected in the duodenal digesta. Blood plasma glycerol content was significantly higher after glycerol application (0.061 mmol l-1 vs. 0.019 mmol l-1). The incorporation of 15N into the rumen bacteria and the proportion of bacterial N (as percent of TCA-precipitable N in the rumen fluid) were lower after glycerol influsion. These results, coupled with the lower concentration of iso-acids (isobutyric and isovaleric acids) in the rumen fluid, indicate that the high amount of glycerol infusion (10% of DMI) reduced protein metabolism of rumen bacteria throughout the experimental period.

[Glycerol as a feed component in fattening pigs]. / Glycerin als Futterkomponente in der Schweinemast.

The production of motor fuel from rapeseed oil forms large amounts of glycerol as a waste product (about 100 g per kg oil). The aim of this experiment was to test glycerol as a component in diets of fattening pigs. In two experiments received 48 pigs (Pietrain x F1, Landrace x German breed) up to 30% glycerol in barley-soya bean oil meal diets. Six pigs per group with an initial weight of 32 kg (experiment 1) and 31.2 kg (experiment 2) in average received the diets semi ad libitum during the whole fattening periods. Barley was replaced by glycerol, that the content of glycerol in diets amounted 5 and 10% (1st exp.) and 5; 10; 20 and 30% in the 2nd exp. respectively. The feed intake was in order of groups up to slaughtering in exp. 1: 1.98; 2.17 and 2.23 kg DM/animal and day and in exp. 2 over 71 days: 2.26; 2.44; 2.54; 2.32 and 2.37 kg DM/animal and day. The sweet taste and the better feed structure of diets with glycerol supplementation is the reason for the higher feed intake in the groups with a glycerol supplement. The daily live weight gain was in the same order 631; 719; 754; 731; 770; 819; 704 and 598 g/animal resp. The feed conversion ratio was only in the group with 30% glycerol significant different from all other groups (3.96 against 2.95-3.30 kg DM/kg live weight gain). 30 min. after feeding the glycerol concentration in blood rose evident with higher glycerol content in diets. It was also found a higher glycerol content in the urine in dependence on the glycerol concentration in the blood. Glycerol in diets changed not the carcass yield and the meat quality. Pathological changes of liver and kidney of animals were not found after glycerol feeding. Amounts of glycerol up to 10% in the diet are recommended.

[In vitro studies on glycerol transformation by rumen microorganisms]. / In vitro Untersuchungen zum Glycerinumsatz durch Pansenmikroorganismen.

Rumen fluid from sheep (non adapted to glycerol) was incubated up to six hours under anaerobic conditions with buffer and mineral solution. Wheat starch was added as substrate in an amount of 1g DM per vessel. Glycerol was additionally admitted to rumen fluid in amounts of 5 to 50% of starch. Carrier-free 14C-glycerol (1.3-labelled) or 15N-labelled NH4Cl were added to different incubation vessels. The disappearance rate of glycerol depended from the amount of added glycerol and incubation time. More than 90% of glycerol disappeared in 2 hours (5% addition), 4 hours (10% addition) and 6 hours (15 to 25% addition) respectively. The sum of volatile fatty acids elevated significant with a higher glycerol addition and 6 hours incubation time. The concentration of propionic acid increased also in dependence of the added glycerol amount and the longer incubation time. The proportion of acetic acid to propionic acid changed from high values (3.5 to 4.0, without glycerol) to the lowest value from 2.5 after 6 hours incubation time and 25% glycerol addition. The most radioactivity of added 14C-glycerol was found in propionic acid and only up to 11% in CO2. 14C-radioactivity was not detected in methane, lactic acid and acetic acid respectively. The 15N-labelling of TCA-precipitable N-fraction was not influenced by glycerol supplementation but the 15N-incorporation in the bacterial nitrogen fraction was lower in the vessels with glycerol.

[The effect of a different protein and fiber intake on the ileal flow of endogenous protein in 15N-labeled swine]. / Untersuchungen zum Einfluss einer unterschiedlichen Protein-und Faseraufnahme auf den ilealen Fluss an endogenem Protein bei 15N-markierten Schweinen.

The endogenous N in ileal digesta of pigs was estimated in two experimental variants. In variant 1 the crud protein content of a wheat-maize-fish meal diet was 18% and the crude fibre content was 1.9% (diet 1) and 2.7% resp. (diet 2). In variant 2 the crude protein content was 12.5% (wheat-maize-diet) and the crude fibre content was 4.1% (diet 3) and 5.5% resp. (diet 4). The higher crude fibre content of the diets 2-4 was provided by means of a supplementation with partially hydroyzed straw meal plus pectin (2:1 w/w). Four miniature pigs with an average initial body weight of 29 kg, were fitted with a ileocaecal re-entrant cannula and received each one of the four different diets. 15NH4Cl, added to the diets, was given for 5 days (150 mg 15N-excess/kg0.75 BW*d) to label the animals with 15N. Ileal digesta, urine and faeces were collected over 24 hours on 8th, 10th and 12th day after the first intake of 15N. The 15N-excess of urine N was used as the comparative measure of 15N-excess of endogenous protein. The amount of nitrogen collected in ileal digesta was in order of the diets 1-4 = 258, 299, 200 and 224 mg/kg0.75 BW*d and of these amounts were 50.1, 52.1, 56.1 and 50.4% of endogenous origin. This were corresponding, after conversion into crude protein to 9.1, 11.2, 10.8 and 11.0 g/100 g crude protein intake or 16.9, 19.7, 13.8 and 13.4 g/kg dry matter intake, respectively. The bacterial N-flow were in order the diets 1-4 = 94.0; 72.7; 55.8 and 52.6 mg/kg0.75 BW*d and 73, 46, 50 and 47% resp. of the endogenous N or 36, 24, 28 and 24% of the ileal total N. The results show, that the absolute amounts of endogenous and bacterial N at the terminal ileum were significantly increased by a higher crude protein content of the diet. The percentage of endogenous and bacterial N on the total N of the ileal digesta was not affected neither by the crude protein content of the diets nor by the fibre supplements.

[Glycerol as feed component and 14C-glycerol metabolism in rats]. / Glycerin als Futterkomponente und 14C-Glycerinumsatz bei Ratten.

Male Wistar rats (initial weight 58 g) received in four groups (10 animals per group) 0.0, 10.6, 21.3, and 31.8% glycerol in the dry matter of the diet (groups 1 to 4). The live weight gain of the animals was, after a feeding time of 3 weeks in the groups 1 to 4, 2.01, 2.49, 2.57, and 2.52 g, respectively, per animal and day. The higher gain in the glycerol groups resulted from the higher feed intake in these groups. Four rats per group received on the 22nd day of the experiment, 1 h after the morning meal, an intraperitoneal injection of carrier-free 14C-glycerol. The 14C-excretion in the respiration air and in the urine was measured in the following 10 h. The 14C-excretion in the 14CO2 of the respiration air was in % of the injected 14C-glycerol doses in the groups 1 to 4 = 45.4, 44.2, 39.0, and 33.2, respectively. The 14C-excretion in the urine was 17.0, 18.1, 25.1, and 32.3%, respectively. The higher values in groups 3 and 4 resulted from the high excretion of free glycerol in the urine. In groups 3 and 4 the glycerol content of the blood plasma was 1.9- and 1.5-fold higher than in groups 1 and 2. It was concluded that up to 40 mg glycerol per hour and animal (100 gLW) was metabolized in a physiological way in group 2. As a feeding component glycerol can constitute up to 10% of the diet-DM in monogastric animals.

[The labeling of feed with 15N as a possibility for the determination of the true N-loss during in situ studies in the rumen of sheep]. / Die 15N-Markierung von Futtermitteln als eine Möglichkeit zur Bestimmung ihres wahren N-Verlustes bei in situ Untersuchungen im Pansen von Schafen.

Green rye (fertilized with 15N) with 37.4% crude fibre, 6.2% crude protein in DM; and 0.31 Atom-%15N-excess (15N') was separated into the fractions stem, leaves and ear. In the same order the fractions had 39.3, 36.4, 27.8% crude fibre; 3.7, 8.1, 11.4% crude protein in the DM and 0.30, 0.27, 0.33 atom-%15N'. Differences in the 15N-label between different nitrogen fractions for one part of the plant (total-N, TCA-precipitable N, pepsin insoluble N) were also measured. The reasons for these results are the once head-fertilization with N and 15N and the following 15N-turnover in the plant. The disappearance rate of DM, N and 15N of different parts of the rye plant was measured using the nylon bag technique in the rumen of sheep. The disappearance rate after a 24-hours incubation period was in the order whole plant, stem, leaves and ear as follows: DM = 44.4; 40.7; 50.3 and 71.6% N = 39.0; -8.5 (N-influx); 55.0 and 80.1% 15N' = 88.4; 84.0 88.3 and 92.4% The label of the N-fraction in the residues of bags was differently reduced in the fractions of plant as a result of influx of foreign N. The largest effect was found for the residues of stem. The reason for this result was interpreted with strong processes of adsorption in the fibrous material for N-molecules and N-compounds. A negatively linear correlation was found between the measured N-disappearance after incubation and the relative differences between the values of the 15N- and N-disappearances. These relative differences achieved negligible values when the N-disappearance was about 80%. The labeling of feedstuffs with 15N is a useful method for the estimation of true N-disappearance in experiments with the nylon bag technique.

[The nitrogen metabolism in the large intestine of ruminants. 8. Metabolism of intracecally infused 15N-urea with a supplement of pectin in heifers]. / Untersuchungen zum Stickstoffumsatz im Dickdarm von Wiederkäuern. 8. Mitteilung--Umsatz von intrazaekal infudiertem 15N-Harnstoff mit Zusatz von Pektin bei Färsen.

Three heifers with live weights of 255, 261 and 300 kg were supplied with ileo-caecal re-entrant cannulas, jugular vena catheters and bladder catheters. The ration consisted of 4 kg maize silage and 4 kg wheat straw pellets. In a previous 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 period the re-entrant cannulas were disrupted and the flowing digesta was quantitatively collected. Precollected digesta and pectin were infused into the distal part of cannula hourly for about 30 hours. During the first 24 hours the digesta was also supplemented with 15N-labelled urea. The amount of pectin corresponded to about 10% of digesta dry mater. An analysis of urine, faeces, digesta and blood plasma were carried out. The application of pectin increased the 15N-incorporation in the bacterial protein of faeces from 4.7% (without supplementation in an earlier experiment) to 10.5% of the introduced 15N. The ammonia-fraction of faeces was markedly higher than the bacterial fraction. The 15N-utilization of urea by the microbes of large intestine was lower in the actual trial evident than with supplementation of starch in the anterior experiment. During the pectin administration the amount of urine increased in comparison with earlier experiments and according to the literature to about the 4.5 fold. The amount of passage of 15N at the ileum cannula (recycled 15N) was 3.8% of the 15N intake. It is the same amount as in experiments in which starch was applied.

[Detection of microbial protein synthesis in the small intestine of sheep using an intraduodenal 15N-urea infusion]. / Nachweis einer mikrobiellen Proteinsynthese im Dünndarm von Schafen mittels einer intraduodenalen 15N-Harnstoffinfusion.

Sheep (3 animals, 50 kg LW) with reentrant cannulas in duodenum and at the end of the ileum received 700 g hay and 800 g alfalfa pellets per animal and day. In a previous 1st period of three days duodenal digesta and in a 2nd period of four days ileal digesta were collected and stored deep frozen. In the main period the digesta flow was interrupted for 28 hours. The duodenal and ileal digesta were collected quantitatively. The previously collected duodenal and ileal digesta portions were introduced hourly. The duodenal digesta was supplemented with 15N-labelled urea for a 24 hour period. 4.5% of the introduced 15N-excess were detected at the end of the ileum in the 24 hour period. 5.6% of the 15N-excess at the end of the ileum were incorporated in bacterial protein. It was measured that the ileal digesta contained 4.62 g N in the TCE precipitable fraction and 24.4% of the TCE precipitable N-fraction was bacterial nitrogen.

[Nitrogen metabolism in the large intestine of ruminants. 7. Metabolism of intracecally-infused 15N urea with supplement of starch in bulls]. / Untersuchungen zum Stickstoffumsatz im Dickdarm von Wiederkäuern. 7. Mitteilung. Umsatz von intrazaekal infundiertem 15N-Harnstoff mit Zusatz von Stärke bei Bullen.

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.

[Nitrogen metabolism in the large intestine of ruminants. 6. Metabolism of intracecally administered 14C and 15N urea in sheep with simultaneous intracecal doses of heat-damaged hay]. / Untersuchungen zum Stickstoffumsatz im Dickdarm von Wiederkäuern. 6. Mitteilung. Umsatz von intrazäkal verabreichtem 14C- und 15N-Harnstoff bei Schafen bei gleichzeitiger intrazäkaler Gabe von hitzegeschädigtem Heu.

Two wethers (28 kg and 33 kg) were supplied with ileocaecal re-entrance cannulae and received a straw pellet ration rich in crude fibre (70.5% straw, 12% chopped sugar beet, 10% cereals, 2% urea, 3% NH4HCO3 and 2.5% of a mineral mixture). In a preliminary period 50% of the digesta flow was collected on 6 successive days for 18 h each. An amount of digesta sufficient for 24 h was apportioned for hourly application and stored at a temperature of -20 degrees C for the main trial. In the main trial the two animals received intracaecally the collected digesta with a supplement of ca. 6 g hay damaged by heat/kg LW(0.75) in hourly portions over 24 h (hay made up ca. 15 and 20% resp. of the DM amount). In addition, each digesta sample was supplemented with 14C and 15N labelled urea (19.7.10(6) Bq 14C urea and 364 mg 15N excess from 15N urea). About 9% of the applied 15N amount was microbially utilized; the utilization quota was thus lower than after the application of partly hydrolyzed straw meal (16% in a previous trial). The 14C activity from 14C urea was quickly eliminated in the form of CO2 in the respiratory gases (at the 18th hour after the end of the infusion 70% excreted as CO2). The half-lives for the urea resulting from the semi-logarithmic decrease of the atom-% 15N excess in the blood plasma were 7.9 and 7.7 resp. 23% and 34% resp. of the applied 15N excess were excreted in urine. The excretion of radioactive carbon in urine, however, was at 2.8% and 4.3% resp. of the applied amount very low 120 h after the beginning of the trial (96 h after the end of the infusion). On the whole one can conclude from this trial that hay damaged by heat has only a low stimulating effect on microbial activity in the large intestine.

[The effect of a reduced drinking water dose on the digestibility of nutrients and several metabolic parameters in sheep. 2. N-balance, water balance and several physiologic parameters]. / Einfluss einer reduzierten Tränkwassergabe auf die Verdaulichkeit von Nährstoffen und einige Stoffwechselparameter beim Schaf. 2. Mitteilung. N-Bilanz, Wasserbilanz und einige physiologische Parameter.

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.

[Influence of reduced water supply on the digestibility of nutrients and on some metabolic parameters in sheep]. / Einfluss einer reduzierten Wassergabe auf die Verdaulichkeit von Nährstoffen und einige Stoffwechselparameter beim Schaf.

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.

[Nitrogen exchange in the large intestine of ruminants. 4. Exchange and isotope balance of intracecally administered 14C- and 15N-urea in sheep with simultaneous intracecal dose of a partly hydrolyzed straw meal]. / Untersuchungen zum Stickstoffumsatz im Dickdarm von Wiederkäuern. 4. Mitteilung. Umsatz und Isotopenbilanz von intrazäkal verabreichtem 14C- und 15N-Harnstoff bei Schafen bei gleichzeitiger intrazäkaler Gabe von teilhydrolysiertem Strohmehl.

Two experiments were performed with wethers (Body weight 34 to 44 kg) receiving a ration rich in crude fibre at maintenance level. The animals were fitted with ileocaecal cannulas into which 14C-, 15N-labelled urea together with digesta was introduced hourly for a 24 hours period (V1; 2 animals). In experiment two (V2; 3 animals) in addition HCl-partly hydrolysed straw meal was introduced. After ureolytic degradation the intracaecal applied urea entered mainly the intermediary metabolism. The resulting ammonia was resynthesized to urea without any time lag. The rate constant for the increase in 15N labelling of urea was 3.2 d-1 in both experiments. Urea leaves the plasma with half lives of 10.6 (V1) and 5.2 (V2) hours. More than 60% of the applied urea were excreted with urine. Formed 14CO2 appeared at proportions of 66% (V2) and 71% (V1) in the respiration gases. Both, the decline of the 14C-activity in blood plasma and the specific 14C-activity of CO2 in the respiration gases after the end of the labelling period do not follow a kinetic of first order. The 15N-labelling of the NH3-N in ileal digesta was very high and reached plateau values similar with those of plasma urea (2.54 vs. 2.56 atom-% 15N-excess). A direct entry of plasma urea into the small intestine was concluded.

[Nitrogen metabolism in the large intestine of ruminants. 3. Microbial utilization of intracecally administered 14C- and 15N-marked urea in the large intestine of sheep in simultaneous intracecal administration of partially hydrolyzed straw meal]. / Untersuchungen zum Stickstoffumsatz im Dickdarm des Wiederkäuers. 3. Mitteilung. Mikrobielle Verwertung von intrazäkal verabreichtem 14C- und 15N-markiertem Harnstoff im Dickdarm von Schafen bei gleichzeitiger intrazäkaler Gabe von teilhydrolysiertem Strohmehl.

Two experiments were performed on sheep, receiving on maintenance level a pelleted straw ration high in crude fibre (straw, 70.5%; dried sugar beet pulp, 12%; cereals, 10%; urea, 2%; ammonium hydrogen carbonate, 3%; minerals 2,5%). The animals were fitted with ileo-caecal re-entrant cannulas. The effects of the introduction of HC1-partly hydrolysed straw meal into the digesta of the large intestine on the digestion processes in that segment were studied. Under these conditions the metabolism of 14C and 15N labelled urea, which was given into the caecum, was estimated. In experiment 1 (E 1; 2 animals) unlabelled, precollected digesta were hourly reintroduced together with 14C and 15N labelled urea via the caecal cannula. In experiment 2 (E 2; 3 animals) the digesta were supplemented with partly hydrolysed straw meal (10% of the mean daily DM-intake with the ration). The supplement of partly hydrolysed straw meal caused an increase of the 15N excretion with faeces from 13.4% (E 1) to 19.8% (E 2) of the dose. The 15N was mainly incorporated in the bacterial fraction (98% E 1; 96% E 2). As a reason for the increased 15N incorporation into the bacterial fraction of 106.4 mg15N' in E 2 vs. 67.3 mg15N' in the experiment without straw meal supplement the higher supply of energy as fermentable carbohydrates was assumed.

[In-vitro studies on the catabolism of acetyl urea in liver tissue]. / In vitro-Untersuchungen zum Azetylharnstoffabbau durch lebergewebe

In vitro-studies were carried out with hepatic tissue from freshley slaughtered cows using 14C acetyl urea (in which the urea-C-atom was labelled). Methods of thin-layer chromatography were used to investigate the process of acetyl urea degradation. The cows had not previouslybeen adapted to acetyl urea. The test mixtures used contained 3.3 mg or 20 mg acetyl urea per 100 ml of the homogenate. The pattern of acetyl urea degradation in these mixtures was investigated after 1 min, 3 mins, 10 mins and 30 mins. The degradation rates were found to be the same for both types of test mixtures. This indicated that a saturation of the substrate had not been accomplished, even when higher concentrations of acetyl urea were used. Supplementary addition of urease to the test mixture for decomposing the quantity of urea always produced did not alter the rates of acetyl urea degradation. From this it may be concluded that even under in vivo-conditions some urea will be liberated when acetyl urea passes through the liver.

[Isobutylidene-di-urea as a new NPN source for ruminants. 2. Metabolism of 14C-15N-isobutylidene-di-urea in sheep]. / Isobutylidendiharnstoff als neue NPN-Quelle für Wiederkäuer. 2. Mitteilung: Stoffwechsel von 14C-15N-Isobutylidendiharnstoff bei Schagen

2 male sheep (weighing 45 kg and 44 kg) were fitted with a ruminal fistula and a jugular vein catheter and received isobutylidendi-urea for a 42-day period of adjustment. The diet contained 25% starch, 23.8% glucose, 29.0% cellulose, 10.0% straw, 1.7% sunflower seed oil, 4.3% isobutylidendi-urea, 5.6% minerals and vitamins. Each animal received 60 g of isobutylidendi-urea in daily amounts of 1.4 kg of the ration-4.4% of the total dietary N came from the straw. At the begin of the trial each sheep received 30 g of 14C15N isobutylidendi-urea (C1-siobutyl labelling) administered as a suspension. The animals were then placedin respiration cages. The peak of specific 14C activity in the expired air (including ruminal gas) was observed 2 hrs after the beginning of the trial. 18--30 hrs after the beginning of the trial the highest level of 15N incorporation into the TCE (trichloroacetic acid) soluble fraction of the ruminal fluid was noted resulting from the reflow of urea via the rumeno-hepatic circulatory system in the rumen. A high concentration of 15N was shown to be present, for prolonged period, in the TCE soluble fraction of the ruminal fluid (up to the 30 hr of experiment). The 15N concentration in the blood plasma (TCE soluble portion) was found to increase reaching a peak value 23 hrs after administration of the isotope. The highest level of 14C activity in this fraction appeared 1 hr after isotope administration. The 15N incorporation into the protein fraction of blood plasma reached a constant high level between the 29th and 47th hr of experiment. The highest 15N concentrations in urine were noted after 1 day. 3.5% of the administered dose of 14C activity and 23% of the supplied amount of N were excreted in the urine. 20% of the total amount of 15N excreted in the urine could be detected as 14C isobutyl residues. An excess of between 0.05 and 0.17 atom% of the isotopes were found in muscular tissue and in different organs of the sheep when these were slaughtered on the 7th day of experiment (liver: 0.17%, kidneys: 0.14%, muscle: 0.05%, heart: 0.08%). The results obtained in the present trial clearly indicate that ruminants are able to utilize nitrogen from isobutyldi-urea.

[Isobutylene diurea as a new source of NPN for ruminants. 1. Nitrogen balance and plasma amino acid composition after feeding of isobutylene diurea to sheep]. / Isobutylidendiharnstoff als neue NPN-Quelle für Wiederkäuer

The paper first presents a survey of the existing literature where studies on the effects of isobutylidene diurea (IBDH) as NPN source for ruminants are discussed. Following this the authors discuss their own experiments on IBDH turnover. IBDH showed no toxi cation when tested in toxicity studies with rats which were carried out under standardized conditions. Within the framework of metabolism trial 4 growing male sheep (average liveweight: 30 kg) were fed a semisynthetic diet containing IBDH as sole N source. Each animal received 60 g IBDH per day. The average value for the apparent N digestibility was found to be 77.6%, the percentage for the average N ballance was 27.6%. The blood of the sheep was investigated, on a comparative basis, for the behaviour of free amino acids after the administration of an experimental semisynthetic diet containing IBDH or extracted soya bean meal as sole N source. The use of IBDH produced a higher concentration of free amino acids and a five-fold increase if urea concentrations in the blood plasma but reduced the Asp, Cys and Tyr levels when compared with the feeding of extracted soya bean meal. Similarly, IBDH supplementation increased the relative proportions of Gly, Lys, and His in blood plasma but reduced those of Asp, Val and Tyr. A positive relationship between the rate of IBDH hydrolysis and the decrease in pH was found in experiments studying the hydrolysis behaviour of IBDH at pH values from 1-7.

[Excretion of acetyl urea in milk following oral 14C-acetyl urea administration to dairy cows]. / Untersuchungen zur Ausscheidung von Azetylharnstoff über die Milch nach oraler 14C-Azetylharnstoffgabe an Milchkühe

2 experimental cows were fed acetyl urea several weeks before the trial was started. The first cow received a daily amount of 200 g and the second cow 855 g. On the first day of experiment both cows were given 5 mCi of 14C acetyl urea intraruminally. Up to 6 hrs after the beginning of the experiment acetyl urea in blood plasma was shown to contain a higher proportion of 14C activity than urea. 0.21 g urea and 0.18 g acetyl urea were contained in 1 kg of milk from cow No 1 while 1 kg of milk from cow No 2 contained 0.18 g urea and 0.12 g acetyl urea. The feeding of acetyl urea to dairy cows is not recommended on the basis of the fact that any further contamination of human nutrition with foreign substances should be possibly avoided.

[Metabolism of 15N-14C-acetylurea in the sheep]. / Der Umsatz von 15N-14C-Azetylharnstoff beim Schaf

3 male sheep (phi 48.3 kg) were fed a semisynthetic diet containing acetyl urea as sole protein source and 15N-14C labelled acetyl urea (urea-C labelled) by intraruminal tube. A half life period of 4 hrs was established for the removal of labelled acetyl urea from the TCE-soluble portion of the ruminal fluid. The degree of 14C labelling in ruminal proteins was very low whereas the extent of 15N labelled protein synthesis was quite marked reaching a maximum between the 18th and 24th hour of experiment. The steepest rise of 15N incorporation into ruminal proteins was found to occur between 8 to 12 hrs after start of the experiment, i.e. at the time of peak level of 15N returned from 15N urea via the rumino-hepatic circulation. 23.3% of the amount of 14C activity administered (mean of all 3 experimental animals) was excreted through respiration. The curve patterns of both isotopes in the TCE soluble portion of the ruminal fluid were similar to that of the degasified TCE soluble portion of the blood blasma. At the peak time (8 hrs) a concentration of the nitrogen isotope of about 4 atom% excess of 15N was observed. The level of 14C labeling in blood plasma proteins was insignificant when compared with that of 15N labelling. The ratio at the peak time was 1:10; the same ratio was found for ruminal proteins. From this it can be concluded that the process of labelling of blood plasma proteins proceeds mainly through microbial protein synthesis. Sheep I and III excreted an average of 60.6% of 14C activity and 57.0% of the administered excess of 15N in the urine. 6 hrs after the beginning of the experiment 81% of the amount of urinary 14C activity was found to occur as acetyl urea; after 48 hrs this amount had decreased to 50%. All experimental sheep excreted a urinary sediment consisting mainly of acetyl urea. The level of faecal 14C excretion (1.4%-2.9% of the amount administered) was considerably lower than that of 15N excretion (9.1%--15.6% of the administered dose). The TCE soluble fraction of the faeces contained up to 2% of the 14C dose and 3% of the 15N dose. The true digestibility data of 15N from 15N acetyl urea varied between 96.4% and 98.2%. An average of 40.9% was obtained for the 15N balance over the 7-day trial period.