Effect of plant oils and aspartate on rumen fermentation in vitro.

The effect of plant oils and aspartate (ASP) on rumen fermentation in vitro. The objective of this study was to determine the effect of plant oils (rapeseed - RO, sunflower - SO; linseed - LO; 10% wt/wt) and 8 mmol sodium aspartate on rumen fermentation of a diet (250 mg) consisting of hay, barley and sugar beet molasses (60 : 30 : 10). Rumen fluid was collected from two Slovak Merino sheep fed the same diet twice daily. Mixed ruminal micro-organisms were incubated in fermentation fluid (40 ml) containing rumen fluid and McDougall's buffer (1 : 4). Incubations were carried out in batch cultures for 72 h at 39 degrees C two times in a 3-week intervals. When compared to the control, all supplemented diets (RO, SO, LO, ASP) significantly increased the pH, the mol% of propionate (LO + 8.7%; SO + 10.12%; RO + 8.65%; ASP + 5.86%) and the acetate : propionate ratio and numerically decreased methane production (SO -32.8%; LO, RO -30.08%; ASP -21.56%). Lactate production was also significantly decreased. Addition of plant oils to aspartate-treated incubations partly inhibited the decrease of n-butyrate, lactate and the increase of pH and in vitro dry matter digestibility (IVDMD) caused by ASP treatment. The effect of combined additives (RO + ASP, SO + ASP, LO + ASP) on methane production SO + ASP (-19.23%) and mol% propionate SO + ASP (+2.66%), LO + ASP (+4.28%) was less effective. All combined additives caused a significant decrease in digestibility of the given feeds. No effect of plant oils and ASP could be observed on the parameters of rumen fermentation (mainly methane and propionate).

[Digestibility of ungraded crude protein from the rumen and of treated protein feeds in the postruminal part of the digestive tracts of ruminants]. / Verdaulichkeit des im Pansen nicht abbaubaren Rohproteinanteils von behandeltem Eiweissfutter im postruminalen Teil des Verdauungstraktes beim Weiderkäuer.

The effective degradability and intestinal digestibility of CP of untreated and with formaldehyde (F) treated sunflower press--cakes (SF), lucerne meal (LM) and field beans (FB) were measured on polycannulated bulls by "in sacco" and "mobile bag" methods. The feeds were treated by F solution in doses from 0.2; 0.4... to 2.0 g F per 100 g CP. The effective CP degradability after treatment was decreased significantly (for SF from 78 to 33%, LM from 73 to 62%, FB from 70 to 47% with max. dose of F). The effect of F was various on individual feeds. The intestinal digestibility of treated feeds, without previous incubation in the rumen, passed from abomasum to feces has been influenced with doses of F non significantly. The digestibility of FB treated with max. dose of F was lower about 20% in the part duodenum feces than in abdomasum feces. The digestibility in the part caecum--feces for all tested feeds has been decreasing with doses of F, similar as in the rumen. The intestinal digestibility of in rumen undegraded crude protein residues of SF has been influenced by the treatment positively. It increased from 43 to 82%. The effect of F on LM was very low. The digestibility has been changed from 75 to 80%.

[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.

[Effect of physical treatment of rapeseed expeller, wheat, corn and corn gluten feed on the degradability in the rumen and the enzymatic in vitro digestibility of nondegraded crude proteins]. / Einfluss der physikalischen Behandlung von Rapsexpeller, Weizen, Mais und Maiskleberfutter auf die Abbaubarkeit im Pansen und die enzymatische in-vitro-Verdaulichkeit des nichtabgebauten Rohproteins.

The influence of physical treatment-expansion and flaking-on crude proteins degradability in the rumen was studied in maize, maize-gluten feed, rape extracted meal and in the expanded one at 120 degrees C and 150 degrees C, rape cake, wheat and flaked wheat by in sacco method. The enzymatic digestibility of crude protein in the rumen undegraded residues of the above mentioned feeds was determined by an enzymatically in vitro method. The treatment of feed decreased significantly the original solubility and theoretical degradability of crude proteins, and the amount of undegraded crude proteins was increased. Positive influence on the amount of enzymatically digested crude protein was determined in rape expanded at 120 degrees C and 150 degrees C (60, 61 and/or 68%). Flaking of wheat had a similar effect. Enzymatic digestibility at undegraded rests where increased by 8-10% after the heat treatment and it remained almost unchanged in expanded maize-gluten feed.

Influence of Avotan on the microflora and concentrations of ammonia and volatile fatty acids in the rumen.

The influence of Avotan (Firm Cyanamid) was studied on VFA concentration, pH, dynamics of NH3 and on numbers of chosen species of rumen microorganisms in physiological experiments with four young bulls and two wethers with rumen cannulas. It was found no marked physiological change in pH of rumen fluid under the influence of Avotan. Difference between groups were statistical significant. Avotan caused significant (P < or = 0.01) decrease of molar % of acetic acid (from 67.0 to 62.1) and an increase of propionic acid (from 16.41 to 28.21 mol %) in wethers. These changes were nonsignificant with bulls. The acetate: propionate ratio decreased significantly from 4.1 to 2.2 in wethers. Avotan decreased highly significantly (P < or = 0.01) the level of NH3 in the rumen fluid during the observed period (0, 1.5, 3, 4.5 and 6 hours after feeding) in bulls. It was observed the similar effect in wethers 3 hours after feeding (from 170 mmol to 81 mmol/l). Decrease of the total number of microorganisms in the rumen fluid was observed in animals which received Avotan (on the average 3.5 times in young bulls, and 4.5 times in wethers). The number of enterococci decreased significantly (2.8-4.5 times), number of amylolytic bacteria decreased less significantly.

[Effect of growth rate of lucerne on the degradability of crude protein in the rumen and on in vitro digestibility of non-degraded crude protein]. / Einfluss des Vegetationsstadiums der Luzerne auf die Abbaubarkeit des Rohproteins im Pansen und die in vitro-Verdaulichkeit des nichtabgebauten Rohproteins.

The influence of growth rate of lucerne was investigated on the content of crude protein, NDF, ADF and the in situ degradability of crude protein and organic matter in the rumen of bulls. The content of crude protein decreased significantly (P < 0.05) with the increasing growth rate of lucerne, simultaneously the part of soluble N as per cent of total N decreased also. The effective degradability of crude protein decreased about 10% and the same value of organic matter about 5% in relation to the increasing content of NDF and ADF (P < 0.01) in dependence of the increasing growth rate of lucerne. The digestibility of non degraded crude protein in the rumen was investigated in vitro with pepsin, trypsin and chymotrypsin. The highest value resulted with 75.0% digestibility for this crude protein fraction in the stage of the start of flowering of lucerne.

[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.

[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.

[Studies on nitrogen metabolism in the large intestine of ruminants. 5. Metabolism of intra-cecally infused 15N-urea without and with fermentable material in heifers]. / Untersuchungen zum Stickstoffumsatz im Dickdarm von Wiederkäuern. 5. Mitteilung. Umsatz von intrazäkal infundiertem 15N-Harnstoff ohne und mit Zusatz von fermentierbarem Material bei Färsen.

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.

Determination of the dry matter disappearance and the crude protein degradability of the formaldehyde treated feeds in the rumen by in situ method.

Sunflower cake (SC), horse bean (HB), and alfalfa meal (AM) were treated with rising doses of formaldehyde (F) from 0.0, 0.2 ... 2.0 g F per 100 g crude protein. We have followed the differences of crude protein solubility, its degradability and disappearance of dry matter in the rumen as well as the amount of reversible bonded F from the F dose. With AM it was found a significant influence of ADF on the degradability and on the amount of acid-labile bonded F and/or on the decrease of N solubility. From the total N content the share of soluble nitrogen decreased in SC by 31%, HB by 24%, and in AM only by 12.5%. With the increase of the F dose its protective effect on proteins against the degradability mainly in SC and HB also rose significantly. The degradability of AM protein was influenced more by the incubation time than by the effect of treatment. The degradability of the SC proteins fell from 95% with untreated to 27% treated with the maximum dose. With AM it fell slowly from 84% to 74% by the determination coefficient R2 = 0.77. It was observed a marked decrease in HB only from the dose of 1.28% F. The changes in dry matter disappearance were similar to the changes in crude protein degradability and to the changes of solubility in SC and AM. The in situ method proved very suitable for the determination of the extent of degradability of the feed proteins in the rumen.

[Production of volatile fatty acids in the rumen of calves during dietary-microbial stimulation and early weaning]. / Produkcia unikavych mastných kyselín v bachore teliat pri dieteticko-mikrobiálnej stimulácii a skrátenom odstave.

The contents of volatile fatty acids in the rumen fluid were studied in calves at an early (seven weeks of age) and traditional weaning term (nine weeks of age). Weaning at the age of seven weeks enabled to save 16.2 kg of milk replacer per calf; there was also a lower content of concentrates in the starter feed with a supplement of Amylastim. The health condition of the calves was good in both groups. The average daily weight gains for the period from the second to the ninth week of age were 0.550 kg in the early weaned calves and 0.690 kg in the calves weaned at a normal time. Early weaning had a positive influence on the development of rumen metabolism. Calves weaned at the age of seven weeks, compared with those weaned at the age of nine weeks, had much higher concentrations of VFA (p less than 0.05) in rumen fluid (at the age of seven weeks: 130.49 mmol per litre vs. 111.53 mmol per litre; at the age of eight weeks: 119.74 mmol per litre vs. 96.98 mmol per litre). Early weaned calves had the statistically significantly (p less than 0.05) higher proportions of propionic acid, butyric acid, i-butyric acid, and valeric acid. Later-weaned calves had the significantly higher (p less than 0.05) contents of acetic acid and i-valeric acid.

Rumen microbial changes in calves fed on alpha amylase diet.

Fifty-six calves in the period of a milk nutrition, randomly assigned to two groups (control and alpha amylase fed) were used to monitor the changes in the rumen microbial populations and total volatile fatty acids (VFA) concentrations associated with feeding Amylosubtilin G10X (0.6 g.day-1). Statistically significant increase was observed for amylolytic counts in experimental calves on 20th or 30th days. The counts of rumen cellulolytic bacteria and selenomonas tended to have increase in the value, but were not significantly different from those in the control valves. The results show that alpha amylase fed calves has a relative higher rumen microbial population.

Study of changes of properties in thermically and hydrothermically treated feeds. 2. N fractions in fermentation medium at the incubation of treated feeds under in vitro conditions.

In the extensive experiments in vitro degradation ability of hydrothermically and thermically treated feeds have been studied. The feeds used were soybean meal, horse bean, alfalfa meal, field pea. The feeds have been treated at 90, 110 and 130 degrees C for 30, 60 and 90 min. The treated feeds have been tested both for microbial degradation ability due to rumen microflora and enzymatic degradation ability via pepsin and trypsin. The fact has been regarded as an important finding that the degradation ability of nitrogenous compounds had been restricted effectively by hydrothermic treatment that was manifested by low ammonia-N levels in fermentation medium (11.3; 8.8; 15.9 and 1.1% out of nitrogen contents in the different feeds). On the other hand improved protein enzymatic digestibility have been recorded in treated feeds as compared with native ones.

[Nitrogen metabolism in the large intestine of ruminants. 2. Metabolism of i.v. infused 15N-urea by additional supply of fermentable material to the large intestine of bulls]. / Untersuchungen zum Stickstoffumsatz im Dickdarm von Wiederkäuern. 2. Mitteilung. Umsatz von i. v.-infundiertem 15N-Harnstoff bei zusätzlicher Versorgung des Dickdarms von Bullen mit fermentierbarem Material.

The experiment was carried out on 3 bulls with body weights of 201, 168 and 190 kg, respectively. The animals were equipped with a ileo caecal re-entrant cannula and with catheters in the jugular veins on both sides. The pelleted ration was composed of straw 70-72%, cereals 10%, molasses 12-41%, ammoniumhydrogencarbonate 3%, urea 2% and mineral mixture 1%. During a preliminary period ileal digesta were collected, deep-freezed and stored. During the main experiment 15N-urea was infused intravenously for 24 hours. In this period and during the following 6 hours outflowing ideal digesta were collected quantitatively. At the same time precollected, unlabelled digesta together with a supplement of partly hydrolysed straw meal were reintroduced into the caecal part of the cannula. Plasma urea-N, urinary-N as well as several N-fractions of faeces and digesta were analysed for 15N abundance. A urea flux rate of 27.9 +/- 3.4 mumol per minute per kg 0.75 was estimated. It was calculated that 52% of this amount of urea was transferred into the digestive tract. In both, digesta and faeces NH3-N was highest 15N-labelled indicating a direct urea entry and degradation in both segments of the digestive tract. The amounts of 15N-excess found during the period of digesta replacement were in faeces 0.25 and in ileal digesta 4.02% of the infused amount of 15N. Although the microbial utilization of endogenous urea-N was generally low in the large intestine there was a clear stimulation of this process due to the additional supply of the large intestine with a fermentable source.

[Nitrogen metabolism in the large intestine of ruminants. 1. Metabolism of i.v. infused 15N-urea without additional carbohydrate supply to the large intestine]. / Untersuchungen zum Stickstoffumsatz im Dickdarm des Wiederkäuers. 1. Mitteilung. Umsatz von i. v. infundiertem 15N-Harnstoff ohne zusätzliche Kohlenhydratversorgung des Dickdarms.

The experiments were carried out on 3 bulls (body weight: 172, 229 and 193 kg), equipped with ileo-caecal cannulas and with catheters in the jugular veins on both sides. The offered pelleted ration consisted of straw 73%, molasses 12%, cereals 10%, ammonium hydrogen carbonate 3% and urea 2%. Feed intake amounted to about 3 kg per animal and day. During a preliminary period of 5 days 50% of ileal digesta were collected for 12 hours daily, deep-freezed and stored. In the main experiment 15N-urea was infused intravenously for 24 hours. During this period and during the following 6 hours ileal digesta were collected and replaced by precollected, unlabelled digesta. The urea metabolism was estimated by the 15N-labelling of blood urea, by the 15N-excretion via faeces and urea, by the appearance of 15N in ileal digesta and by the 15N-labelling of faecal NAN, NH3 and bacterial fraction. The time course of the 15N-labelling of plasma urea during infusion can be described by an exponential function. The urea flux rate was estimated from the calculated plateau value. The flux rate for the 3 animals was 28.8, 30.7 and 34.8 mumol per minute per kg0.75, respectively. During the infusion of 15N-urea 1.0-2.4% of the infused amount of 15N' appeared in ileal digesta, half of it in the TCA precipitable fraction. At the same time the 15N-labelling of faecal NH3 increased sharply, however, the 15N-labelling of the faecal bacterial fraction was smaller by one order of magnitude. Deficiency of fermentable substrates and problems of inhomogenity of the NH3 pool are supposed as reasons for this result. 30 to 50% of the urea flux entered the digestive tract, the direct entry of urea into the large intestine seems to be only very low.

[Effect of the content of crude plant protein in the ration on the utilization of urea in dairy cattle. 2. 15N-urea metabolism]. / Untersuchungen zum Einfluss des Gehaltes an pflanzlichem Rohprotein in der Ration auf die Verwertung von Harnstoff bei der Milchkuh.

The metabolism of 15N-urea in the rations of dairy cows was investigated in dependence on the crude protein content of the rations. With energy concentration remaining unchanged, the rations contained 10.7 (I), 13.7 (II) and 17.1 (III)% plant crude protein and, after the supplementation of 150 g urea per animal and day, a total of 13.8, 16.7 and 20.2% crude protein in the dry matter. The urea was intraruminally infused during the feeding in the morning and the evening. In the morning feeding of each 1st measuring day it was labelled with 27.5 atom-% 15N-excess (15N'). The degree of labelling with 15N' of the N-fraction of rumen fluid, contents of the duodenum, faeces and milk, precipitable with trichloric acetic acid (TCA) decreased with the rising protein level of the ration. This effect was bigger than could be expected considering the low 15N'-quota in the total-N of the ration. In the sequence I ... III, 52.7, 32.2 and 30.6% of the 15N'-amount taken in passed the duodenal re-entrant cannula in TCA-precipitable form within 72 hours after the 15N-application. 33.3, 21.9 and 22.6% were apparently absorbed in the intestines as TCA-precipitable N within 120 h after the 15N'-application. In the same period 31.7, 43.1 and 72.8% of the 15N' taken in were excreted in urine. 12.3, 9.6 and 5.8% of the applied 15N' were found in milk protein. One can conclude that the utilisation of urea-N decreases with the rising level of crude protein in the ration and that, however, urea-N is still biochemically utilised when there is an excess of plant-N in the ration.

[Effect of the content of plant crude protein in the ration on the utilization of urea by the milk cow. 1. Nitrogen digestibility and utilization of urea for bacterial protein synthesis in the rumen]. / Untersuchungen zum Einfluss des Gehaltes an pflanzlichem Roh-protein in der Ration auf die Verwertung von Harnstoff bei der Milchkuh. 1. Mitteilung. Stickstoffverdauung und Verwertung des Harnstoffs für die bakterielle Proteinsynthese im Pansen.

The utilisation of feed urea in the rumen was tested in 2 experiments with a total of 4 newly lactating dairy cows (13 . . . 15 and 17 . . . 19 kg resp. milk/animal and day) with rumen and duodenal re-entrant cannulae. With the energy supply remaining constant in each case, the rations in experiment A contained 8.7, 12.4 and 14.6 and those of experiment B 10.7, 13,7 and 17.1% crude plant protein in the dry matter. After the supplementation with 120 and 150 g resp. urea/animal and day there were 11.9, 15.7 and 17.8 (A) and 13.8, 16.7 and 20.2 (B) % resp. crude protein in the dry matter. The rations consisted of maize silage and a pelleted mixture of straw and concentrated feed (A) resp. maize silage, alfalfa hay and concentrated feed (B). They contained 10.3 . . . 10.6 (A) and 13.6 (B) kg dry matter with 5.6 . . . 6.0 (A) and 8.2 (B). With the increase of the crude protein level of the ration to 16.7 . . . 17.8, the absolute amount of non-NH3-N (NAN) in the duodenum increased as well. Between N-intake (g/d, x) and NAN-passage corrected by the amount of the endogenous quota (g/d, y) the relation y = 87.3 + 0.55 x (r = 0.80) could be established. NAN-passage (y) as related to N-intake decreased with the N-concentration in the dry matter of the ration (x) according to the equation y = 0.35 + 1.22x-1 (r = 0.57). 70, 62 and 61% (experiment A) and 55, 61 and 51% (experiment B) of the consumed amount of N were apparently absorbed in the intestines as NAN (without endogenous quota). The bacterial N-yield of the rumen (g, y), determined with diamino pimelic acid as microbe marker, was dependent on the consumed digestible organic matter (g, x) as follows: y = 67.3 + 0.021x (r = 0.69). There was no connection with the level of N-supply. The measuring results of the bacterial N-yield show that the utilisation rate of the urea-N decreased rapidly when there was more than 11 . . . 12% crude plant protein in the dry matter of the ration. For the tested ration type (570 . . . 600 EFUcattle/kg dry matter) the urea utilisation potential in the rumen for crude plant protein concentrations of 8.7, 10.7, 12.4, 13.4, 13.7, 14.6 and 17.1% in the dry matter was 13.0, 6.9, 4.1, 2.6, 1.3 and -9.6 g urea/kg dry matter.