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At least 577 records · Page 32Linked to original sources
PubMed1982

Estimation of the proportion of non-ammonia-nitrogen reaching the lower gut of the ruminant derived from bacterial and protozoal nitrogen.

1. A method for estimating the proportions of bacterial- and protozoal-N in the total non-ammonia-N reaching the lower gut of the ruminant under steady-state conditions was evaluated. Three trials using two different diets were conducted with a Holstein steer equipped with a rumen cannula and duodenal re-entrant cannulas. 2. An intraruminal primed infusion of (15NH4)2SO4 was administered for 68 h during each trial. Bacteria and protozoa samples were isolated from rumen fluid at approximately 6 h intervals during each infusion period. Total non-ammonia-N was isolated from duodenal digesta samples taken at approximately the same times. All of these samples were analysed for 15N enrichment. A computer program was used to fit equations to the 15N-enrichment curves of bacterial- and protozoal-N. Models of both bacterial- and protozoal-N kinetics consisted of a small pool which equilibrated rapidly with rumen NH3 and a large pool with a fractional turnover rate of 0.045-0.070/h for bacterial-N and 0.056-0.069/h for protozoal-N. 3. Abomasal fluid turnover was estimated by a single injection of polyethylene glycol (molecular weight 4000) into the rumen followed by sampling of rumen fluid and duodenal digesta. 4. Estimates of abomasal fluid turnover, bacterial-N turnover, and protozoal-N turnover were entered into an equation which was adjusted by computer iteration to fit the 15N-enrichment curve of duodenal digesta non-NH3-N generated from each (15NH4)2SO4 infusion period. The computer fit of this equation to the observed results gave estimates of 0:39-0.45 and 0.22-0.41 for the proportion of duodenal non-NH3-N derived from bacterial-N and protozoal-N respectively. 5. This method is potentially useful in estimating microbial protein passage to the lower gut in ruminants. Sampling digesta from the omasum rather than the duodenum would simplify the method and possibly increase the reliability of the estimates.

Abomasum↗
PubMed2001

Are the proposed limits of energy intake:basal metabolic rate and dietary nitrogen:urinary nitrogen ratios suitable for validation of food intake?

The validity of 7 d weighed records of diet obtained for pre-menopausal Mexican women was assessed by two independent methods: the energy intake:BMR (EI:BMR) and the dietary N:urinary N (DN:UN). For the latter, complete urine collections are required and completeness was assessed from measurements of para-aminobenzoic acid (PABA) excretion. There were forty-six adult female subjects in the study, thirty-four were from Mexico City and twelve were from a rural population in the Central Highlands, Mexico. However, data were rejected from five urban women for whom the PABA excretion data suggested incomplete urine collection on four or more days. BMR was measured with Oxylog portable O2 consumption meters, and physical activity level was assessed from a self-completed activity diary. An approximate relationship between the EI:BMR ratio and the DN:UN ratio suggested that the rejection limits on the EI:BMR ratio recommended by are wider than the limits on the DN:UN ratio recommended by. Using the recommended cut-off points for EI:BMR but wider limits for DN:UN, twenty-one and twenty-five women respectively had acceptable intake records by the two methods, and sixteen of them by both methods. In conclusion the modification of the DN:UN limits to 0.92 and 1.70 to set acceptable intake values makes the use of measurements of N and energy balance comparable. Urine values with PABA recoveries greater than should be rejected, as should UN values validated by less than 3 d.

Adult↗
PubMedDate not supplied

[Blood urea concentration, a parameter for the assessment of protein metabolism in pregnant sows. 2. Relations between blood urea concentration and urine nitrogen excretion as well as estimation of urine nitrogen excretion from the blood urea concentration].

The influence of supplementing the ration with the limiting amino acid lysine on N-excretion in urine and the urea concentration in the blood (UCB) is investigated in an experiment with pregnant young sows. In contrast or the basic ration the most satisfactory N-utilisation reflects itself after a lysine intake of 8.2 g/animal and day during the early phase of gestation and 8.6 g during the last phase of gestation both in a diminished N-excretion in urine and a lower UCB. The following correlation coefficients were calculated for the relation between UCB an N-excretion in urine: early phase of gestation: 0.177 (n = 37); last phase of gestation. 0.431 (n = 30); gestation as a whole: 0.416 (n = 67). In a second experiment methionine supplementation in the feeding of a ration with a deficit of sulphur-containing amino acids led to a significant decrease of N-excretion in urine (alpha = 5%). While UCB also significantly decreased 5 hours after feeding, UCB virtually did not react to a changed level of amino acid intake when the blood sample was taken before feeding. In a third experiment, in which 49 g N/animal and day were taken in, differences regarding N-excretion in urine and UCB between pregnant and non-pregnant animals could not be established. When the results published in the first communication (Herrmann and Schneider, 1981) are included, the following correlation coefficients for the relation between N-excretion in urine and UCB are the result: 0.716 (n = 182) for sampling before feeding and 0.808 (n = 133) for sampling 5 hours after feeding. The confidence range of the estimated function y = -2.97 + 1.233 chi for the relation between N-excretion in urine (y; g/animal and day) and UCB 5 hours after feeding (chi; mg/100 ml serum) as well as the variability values do not make it possible to estimate N-excretion in urine from UCB with satisfactory accuracy.

Animals↗
PubMed1985

[Nitrogen and amino acid resorption in the small intestine of growing swine. 1. Animal study method, nitrogen content and amino acid composition of the small intestine chyme by administration of various proteins].

The amount of endogenous N in the chyme at the end of the small intestine and the amino acid composition of the ileum chyme were ascertained with growing pigs with ileorectostomy after feeding qualitatively differentiated protein sources. In dependence on the protein used, distinct differences turned out for some amino acids with regard to their content in the ileum chyme. Bacteriologic and histologic investigations subsequent to the dissection of the test animals showed that - in comparison to the control animals-the functions of the small intestine remained the same during the time of the experiment. The experiment method described appears to be suitable for absorption investigations up to the end of the small intestine of growing pigs.

Amino Acids↗
PubMed2005

Nitrogen supply after removing the shoot apex increases the nicotine concentration and nitrogen content of tobacco plants.

BACKGROUND: and Aims High nicotine concentrations in leaves, especially in the upper leaves, offer a serious problem for the cultivation of tobacco (Nicotiana tabacum). Preliminary field experiments showed that rapid mineralization of soil N during late stages of growth may contribute to high nicotine concentrations in leaves. METHODS: A sand-culture experiment was carried out in the greenhouse. The N supply was controlled during the experiment, and different amounts of 15N were supplied during late stages of growth (after removal of the shoot apex), to investigate the contribution of the N taken up at this time to the N content of and nicotine concentration in tobacco plants. KEY RESULTS: Addition of 1.6 g or 4 g 15N-labelled NH4NO3 after removing the shoot apex and flushing out the 14N did not increase leaf dry weights; however, it did result in delayed leaf senescence, more lateral bud formation, and an increase in 15N as a proportion of total N, and nicotine-15N as a proportion of total nicotine-N in each organ. The nicotine concentration, 15N and nicotine-15N abundances were increased from the bottom to the top leaves. When more 15N-labelled NH4NO3 was supplied, the nicotine concentration in leaves increased, and so did the 15N abundance in nicotine-N. CONCLUSION: Enhanced N supply in the later growth stages (after removing the apex) increased N content and nicotine concentration in tobacco plants. Nicotine was synthesized de novo during the late growth stages.

Nicotine↗
PubMed2001

Nitrogen nutrition and the role of root-shoot nitrogen signalling particularly in symbiotic systems.

To obtain and concentrate reduced N from the environment, plants have evolved a diverse array of adaptations to utilize soil, biotic and atmospheric N. In symbiotic N(2)-fixing systems the potential for oversupply exists and regulation of activity to match demand is crucial. N status in plants is likely to be most strongly sensed in the shoot and signals translocated to the roots may involve phloem transported amino compounds or very low concentrations of specific signal molecules. The mechanism for sensing N status in plant cells is not understood at the molecular level although it may be expected to be similar in all plants. Mechanisms for the regulation of symbiotic N(2) fixation may be very different in the different symbiotic types. Rhizobia, Frankia and cyanobacteria are all symbiotic with different species of plants and the provision of O(2), carbohydrate or other nutrients may control symbiotic activity to varying extents in the different symbioses.

Adaptation, Physiological↗