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.

[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.

[15N-labeling of fishes using 15N isotopes in aquarium water and the effect of a different protein nutrient on the 15N elimination after the labeling period]. / 15N-Markierung von Fischen über 15N-isotope im Aquarienwasser und der Einfluss einer unterschiedlichen Eiweissernährung auf die 15N-Eliminierung nach der Markierungsperiode.

In a preexperiment of 12 days fishes (Cyprinus carpio L.) were labelled with 15N by means of 15NH4Cl and 15N-urea resp. in the aquarium water and by feeding a protein free diet. 15NH4Cl yielded a higher atom-% 15N excess (15N') in the tissues of fishes. In the main experiment 75 fishes (Cyprinus carpio L.) were 15N-labelled with 100 mg 15N'/l water from 15NH4Cl (95 atom-% 15N') in a protein free preperiod of 12 days. In the following main period the fishes received different protein sources in their diets in maintenance. A group of 20 fishes received an animal protein (fish meal) and two groups of 20 fishes each received plant proteins (soybean meal and wheat gluten resp.). The atom-% 15N' reached after the 15N-labelling period following values: digestive tract with content--7.15, liver--5.65, gills--5.89, muscle--0.81 and chorda dorsalis--1.09 respectively. During the main period (with protein feeding) the atom-% 15N' decreased in the tissues with high protein turnover (liver and gills) on the 2nd and 4th day to 4.31 +/- 0.11 (animal protein) and 4.64 +/- 0.14 (plant proteins) in average. The corresponding values in the tissues with low protein turnover (muscle and chorda dorsalis) were 0.73 +/- 0.04 and 0.80 +/- 0.04 atom-% 15N' in average. From the measurements on the 6th, 8th and 10th day of protein feeding resulted an atom-% 15N' in average of liver and gills of 4.08 +/- 0.13 (animal protein) and 4.11 +/- 0.15 (plant proteins). In muscle and chorda dorsalis the atom-% 15N' ascended in this time upon 0.80 +/- 0.04 (animal protein) and 0.90 +/- 0.03 (plant proteins). It seems that the protein metabolism of fishes is favoured from the amino acid of plant protein in comparison to animal protein to reduce the 15N-loss of the 15N-labelled body in maintenance, like the results from experiments with rats (Hernandez et al., 1981).

[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.

[Postileal nutrient digestibility in cattle]. / Untersuchungen zur postilealen Nährstoffverdaulichkeit bei Rindern.

Four heifers of an average live weight of 301 kg supplied with ileocaecal re-entrant cannulae received rations consisting of 4 kg hay (variants A und B), 1 kg coarse wheat meal, 0.4 kg molasses, 100 g urea and 30 g mixed minerals per animal and day. After a 14-day preliminary feeding period the ileum digesta was quantitatively collected at the re-entrant cannula over 24 h. 10% of the digesta were used for analysis, the remainder was heated to 37 degrees C and returned. Under consideration of the digesta passage through the colon the 24-hour collection of faeces was started after a 6-hour delay after the first replacement of digesta. Losses of nutrients were calculated from the values analysed from digesta and faeces. No differences could be ascertained between the two hay variants. On an average of the two rations the nutrient losses of the scaffold substances-equivalent to the digestibility in the colon-showed the following values: crude fibre = 10.6%, NDF = 10.4%, ADF = 11.9% and hemicellulose = 7.4%. The losses of the other nutrients, corresponding to their apparent digestibility, had the following values: crude protein = 12.1%, crude fat = 10.7%, N-free extracts = 18.9%, ash = 31.2%, dry matter = 17.5%. The water balance showed that 8.2 l water of the 23.4 l supplied with the ileum digesta were excreted in faeces.

[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.