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PubMed2004

Regional inventory of soil surface nitrogen balances in Indian agriculture (2000-2001).

Nitrogen regulates several ecological and biogeochemical processes and excess reactive nitrogen in the environment can lead to pollution problems, including the deterioration of air quality, disruption of forest processes, acidification of lakes and streams, and degradation of coastal waters. Much of the excess nitrogen inputs are related to food and energy production. An important step to understanding the sources of nitrogen and ultimately defining solutions to excess nitrogen is to describe the geographic distribution of agricultural nitrogen contributions from different regions. In this study, soil surface nitrogen loads were quantified for different states of India for the period 2000-2001. Nearly 35.4 Tg of nitrogen has been estimated as inputs from different sources, with output nitrogen from harvested crops of about 21.20 Tg. The soil surface nitrogen balance, estimated as inputs minus outputs, is found to be about 14.4 Tg surplus from the agricultural land of India. Livestock manure constituted a major percentage of total inputs (44.06%), followed by inorganic fertilizer (32.48%), atmospheric deposition (11.86%) and nitrogen fixation (11.58%). Nitrogen balance varied from deficit to surplus for different states. The highest nitrogen surplus was found in Uttar Pradesh (2.50 Tg) followed by Madhya Pradesh (1.83 Tg), Andhra Pradesh (1.79 Tg), etc. A negative nitrogen balance was found in Orissa (-0.01 Tg), Andaman Nicobar Islands (-0.32 Tg) and for some of the northeastern states. Major fertilizer consumption states were found to be Tamilnadu (204 kg/ha), Haryana (132 kg/ha), Punjab (148 kg/ha), followed by others. Similarly, nitrogen inputs from total livestock excretions were found to be high for Kerala (616 kg/ha), Jammu and Kashmir (389 kg/ha), Tamil Nadu (338 kg/ha), etc. The average nitrogen surplus of about 54 kg/ha observed for the agricultural land of the entire country of India is comparatively higher than the average surplus of about 31 kg/ha reported for European countries. These results, obtained from nutrient mass balance calculations, will be useful to formulate nutrient management plans relating to fertilizer usage, livestock management and for adopting some best management strategies at a state level in India.

Agriculture↗
PubMed2003

Nitrogen utilization in a vapor-phase biofilter.

The effect of media nitrogen levels on biofilter performance was investigated in a lab-scale biofilter treating toluene and p-xylene. Nitrogen utilization rates and the quantity of nitrogen recycled to meet microbial demand in the biofilm were estimated using a nitrogen balance approach. Experimental data imply that overall biofilter performance was a strong function of normalized nitrogen levels in the synthetic media. The biodegradation of p-xylene was found to be more sensitive to media nitrogen levels than was the degradation of toluene. However, increasing the nitrogen supply improved both toluene (>99%) and p-xylene removal efficiencies (>90%). Nitrogen balance calculations indicate that substantial recycling of nitrogen occurred in the biofilm even under nitrogen-rich conditions. The fraction of nitrogen demand met by recycling nitrogen increased when the external supply of nitrogen was terminated, and the biofilm became nitrogen limited. However, to avoid severe nitrogen limitation conditions, an external nitrogen source must be provided to sustain high pollutant removals in the biofilter.

Air Pollution↗
PubMedDate not supplied

Urinary nitrogen constituents in the postsurgical preterm neonate receiving parenteral nutrition.

Minimal information is available defining urinary nitrogen constituents in preterm neonates receiving parenteral nutrition (PN). The study objective was to evaluate 24-hour urine collections for total urinary nitrogen (TUN), urinary urea nitrogen (UUN), and the nitrogen content in creatinine, ammonia, free amino acids, protein, hippuric acid, and uric acid at baseline (days 1 to 2 of PN and days 1 to 3 after surgery) and 7 days later in eight preterm, postsurgical neonates. Calculation of undetermined nitrogen was also completed. Comparisons with historic, normal data were made for each urinary nitrogen constituent. At baseline, PN provided 59 +/- 10 nonprotein kcal/kg.day-1 and 430 +/- 54 mg/kg.day-1. At day 7, PN provided 106 +/- 23 nonprotein kcal/kg.day-1 and 432 +/- 30 mg/kg.day-1. TUN, UUN, and protein nitrogen decreased significantly from baseline at day 7 (p < .05). The percentages of TUN as amino acids, creatinine, and uric acid nitrogen were calculated. Percent amino acid nitrogen (6.0 +/- 2.3% vs 8.4 +/- 1.5%, p < .05), percent creatinine nitrogen (1.6 +/- 0.5% vs 2.9 +/- 0.8%, p < .001) and percent uric acid nitrogen (1.7 +/- 0.9% vs 3.6 +/- 2.1%, p < .05) increased significantly at day 7. The observed urinary free amino acid nitrogen fraction represented a higher percentage of TUN both at baseline and at day 7 when compared with term neonatal reference data, whereas creatinine nitrogen, uric acid nitrogen, and protein nitrogen represented a lower percentage of TUN. However, amino acid and creatinine nitrogen as a percentage of TUN were similar to levels in milk formula-fed preterm infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1995

Partition of nitrogenous substances in the urine of sheep on different dietary protein intakes.

The distribution of nitrogenous substances in urine was studied in sheep fed high (28.71 g N daily) and low (9.32 g N daily) protein diets for 6-8 weeks. The concentrations of total nitrogen and urea, allantoin, free amino acids, uric acid, hippuric acid, creatinine, creatine and ammonia were measured in urine. The nitrogen content of these measured substances was calculated. The results showed that the concentrations of total urinary nitrogen and nitrogen of individual nitrogenous substances were lower in sheep on a low protein diet, except for uric acid nitrogen which was unchanged. Urea nitrogen was responsible for up to 74% of the total urinary nitrogen of both groups of animals without any significant difference. The individual nitrogen portions of nitrogenous substances other than urea in total urinary-N did not exceed 7% during the intake of both diets. The intake of a low protein diet resulted in a significant increase in the proportion of nitrogen from uric acid, hippuric acid, creatinine and free amino acids, while the fraction of ammonia nitrogen in the total urinary N was significantly reduced. It is concluded that different protein or nitrogen intake in the diet do not have any significant effect on the urea nitrogen fraction in the total urinary nitrogen of sheep.

Analysis of Variance↗
PubMedDate not supplied

Nitrogen loads to estuaries from waste water plumes: modeling and isotopic approaches.

We developed, and applied in two sites, novel methods to measure ground water-borne nitrogen loads to receiving estuaries from plumes resulting from land disposal of waste water treatment plant (WWTP) effluent. In addition, we quantified nitrogen losses from WWTP effluent during transport through watersheds. WWTP load to receiving water was estimated as the difference between total measured ground water-transported nitrogen load and modeled load from major nitrogen sources other than the WWTP. To test estimated WWTP loads, we applied two additional methods. First, we quantified total annual waste water nitrogen load from watersheds based on nitrogen stable isotopic signatures of primary producers in receiving water. Second, we used published data on ground water nitrogen concentrations in an array of wells to estimate dimensions of the plume and quantify the annual mass of nitrogen transported within the plume. Loss of nitrogen during transport through the watershed was estimated as the difference between the annual mass of nitrogen applied to watersheds as treatment plant effluent and the estimated nitrogen load reaching receiving water. In one plume, we corroborated our estimated nitrogen loss in watersheds using data from multiple-level sampling wells to calculate the loss of nitrogen relative to a conservative tracer. The results suggest that nitrogen from the plumes is discharging to the estuaries but that substantial nitrogen loss occurs during transport through the watersheds. The measured vs. modeled and stable isotopic approaches, in comparison to the plume mapping approach, may more reliably quantify ground water-transported WWTP loads to estuaries.

Environmental Monitoring↗
PubMed1984

Net absorption of glucose and nitrogenous compounds by lactating Holstein cows.

Net absorptions from portal-drained viscera of glucose, ammonia nitrogen, alpha-amino nitrogen, and urea nitrogen were measured in four Holstein cows in first lactations. Cows were fed for ad libitum consumption a completely mixed, 60:40 corn silage:supplement diet (dry basis) in two equal feedings at 12-h intervals daily. Portal blood flow (dye dilution) and net absorption (portal-arterial difference times portal blood flow) were measured at hourly intervals for 12 h for all cows 4 and 8 wk postpartum and for two cows 4, 8, 12, 16, and 20 wk postpartum. Apparent digestibilities of dry matter and nitrogen were measured immediately after net absorption. Milk yield and composition were measured with absorption and digestion. Mean daily dry matter intake and milk yield were 14.1 +/- .6 and 23.8 +/- 1.8 kg. Portal blood flow was not affected by time of day or weeks postpartum; mean was 1371 +/- 123 liters/h. Net absorption of glucose was negative, indicating no uptake of glucose from dietary sources. Means (g/day) for nitrogenous sources were: nitrogen intake 387, fecal nitrogen 121, urinary nitrogen 146, milk nitrogen 116, net ammonia nitrogen absorption 149, net alpha-amino nitrogen absorption 137, and net loss of urea nitrogen from blood to the gut 93. Net absorption of amino nitrogen and alpha-amino nitrogen in blood was greater than in plasma; corresponding losses of urea nitrogen and glucose to the gut were greater from blood than plasma.

Amines↗
PubMed1996

Protein nitrogen appearance in CAPD patients: what is the best formula?

BACKGROUND: The protein equivalent of nitrogen appearance is an indirect index commonly used to assess dietary protein intake in patients on CAPD. Moreover it has been suggested that the ratio between nitrogen appearance and dietary nitrogen intake (fractional urea synthesis) can predict nitrogen balance in uraemic patients. Several formulae to directly calculate the protein equivalent of nitrogen appearance have been published. It has not been established, however, what formulae give the most appropriate estimate of protein intake and nitrogen appearance. STUDY DESIGN: Nitrogen balance studies were carried out in seven stable patients on CAPD. All of the patients were receiving a diet whose protein content (1.2 g/kg/body wt/day) and calorie content (35 kcal/kg/body wt/day) were rigorously controlled. Six formulae for calculating protein equivalent of nitrogen appearance and nitrogen appearance were tested and the agreement of the estimating formulae was evaluated by means of the Bland and Altman method. RESULT: Net nitrogen balance was 1.68 +/- 0.9 g/N day, protein intake (g/day) 81 +/- 19, protein intake (g/kg) 1.05 +/- 0.17. Differences in protein equivalent of nitrogen appearance of up to about 20% were found. The smallest differences between protein equivalent of nitrogen appearance and protein intake were obtained by the formulae of Bergstrom (1 +/- 7 g, limits of agreement -12 and +15 g) and Blumenkrantz (-2 +/- 5 g, limits of agreement -11 and +7 g). The formula of Bergstrom most closely estimated nitrogen appearance (-0.35 +/- 0.89 g). Using such formula, the fractional urea synthesis was 54 +/- 12%, giving evidence of positive nitrogen balances. CONCLUSION: For the routine monitoring of protein equivalent of nitrogen appearance in CAPD patients, we recommend Bergstrom's formula with the determination of dialysate protein losses.

Blood Urea Nitrogen↗
PubMed1981

Nitrate and nitrogen balances in men.

Nitrate is a nitrogen-containing compound that is not detected by the traditional Kjeldahl method of nitrogen analysis. Nitrate balance studies were done in order to determine if nitrate production in the human body contributes to the irrationally positive nitrogen balances that have been reported in healthy adults. Seven healthy young men, confined to a metabolic unit, received five diets for 9 days each: a mixed foods diet, a fiber-free egg formula diet, and egg formula with California small white beans, lima beans, and wheat bran added. Nitrate-nitrogen intake with the mixed foods diet was 75 mg/day and nonnitrate nitrogen intake was 19 g/day; crude Kjeldahl nitrogen balance (intake--(urinary + fecal)) was 0.64 +/- 1.23 g/day. Nitrate-nitrogen excretion exceeded intake by 0.10 +/- 0.05 g/day. With the four other diets, nitrate-nitrogen intake was almost nil (about 2 mg/day) and nonnitrate nitrogen intake was 95 mg/kg body weight; crude Kjeldahl nitrogen balances ranged from -0.63 +/- 0.73 to 0.02 +/- 0.45 g N/day. With these four diets, feces contained about 80 mg nitrate-nitrogen/day and urine contained about 8 mg. Saliva obtained before lunch had about 1 ppm nitrate-nitrogen with the formula diets and 5 ppm with the mixed foods diet. Net synthesis of nitrate is quite variable but appears to be of the order of 100 mg nitrate-nitrogen/day. Although the excess nitrate excretion increased total nitrogen excretion by less than 5%, it could account for as much as 10 to 20% of unexplained positive nitrogen balances previously reported in well-controlled studies.

Adult↗
PubMed1983

Nitrogen requirement of amino acid mixture with maintenance energy in young men.

The effect of energy on nitrogen balance was examined in young men given amino acid mixture. The minimum amino acid nitrogen requirement for nitrogen equilibrium was determined together with the egg protein requirement. In experiment 1, the nitrogen sparing effect of energy was evaluated in four male students receiving diet containing an amino acid mixture and a constant nitrogen intake of 3.5 g N/day, which was equivalent to the nitrogen requirement with excess energy intake determined by Rose and Wixom (1). When the dietary energy supply was 45 kcal/kg, which is approximately the maintenance level, the mean nitrogen balance was negative, being -23.9 +/- 9.3 mg N/kg. However, with an excess energy intake of 55 kcal/kg, the nitrogen balance improved significantly, being -6.1 +/- 7.7 mg N/kg. In experiment 2, the nitrogen requirement of egg-pattern amino acid mixture for apparently zero balance was evaluated at maintenance energy intake in 28 Japanese young men and was compared with that of egg protein. After receiving standard diet, the subjects were given a semi-purified experimental diet containing egg-pattern amino acid mixture at nitrogen intake levels of 60, 75, 100, and 130 mg N/kg for two weeks. Then all groups except the 60 mg N/kg group were given isonitrogenous egg protein diet for another week. Energy intake was kept constant at approximately the maintenance level of 44.4 +/- 1.4 kcal/kg throughout the experiment. Nitrogen balance was not significantly different in groups given egg-pattern amino acid mixture and intact egg protein in each nitrogen intake level. From regression analysis, the nitrogen requirement for nitrogen equilibrium of the amino acid mixture was calculated to be 110.1 +/- 50.2 mg N/kg, which was not significantly different from the value of 88.4 +/- 40.6 mg N/kg of egg protein. It was concluded that the total amino acid requirement estimated by Rose and Wixom (1) was too low because they gave excess energy, and that there was no difference between the nitrogen requirement of egg protein and that of the corresponding amino acid mixture.

Adult↗
PubMed2003

Nitrogen purity influences the occurrence of As+ ions in high-performance liquid chromatography/electrospray ionization mass spectrometric analysis of four common arsenosugars.

High-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC/ESI-MS) can provide both elemental and molecular information and, therefore, is a very useful tool for the identification of arsenic compounds. When a method for the identification of four arsenosugars was employed in our laboratory with an HPLC/ESI-MS system equipped with a Whatman model 75-72 nitrogen generator, a signal at m/z 75 (As(+)) could not be observed. When the HPLC/ESI-MS system was operated with nitrogen 5.0 (nitrogen of a purity of at least 99.999%) all four arsenosugars gave a signal at m/z 75. Because of this observation the influence of the quality of the nitrogen drying gas on the fragmentation of the four arsenosugars was systematically investigated. Standard solutions containing the four arsenosugars (0.5 ng As each) were separated on an anion-exchange column and detected with ESI-MS in the positive ion mode by monitoring the signals for [M+H](+), m/z 237, 91, and 75. Nitrogen with defined oxygen concentrations was used as drying gas. The purity of the nitrogen ranged from 99 to 99.999% (10 400 to 10 ppm oxygen impurity). The nitrogen with 99% purity gave no signal at m/z 75, but signals were obtained at m/z 91, 237, and for [M+H](+). When higher purity nitrogen (99.9%) was used, a signal was obtained at m/z 75, which accounted for 0.8-1.1% (depending on the kind of arsenosugar) of the sum of the signals for m/z 75, 91, 237 and [M+H](+). As the level of oxygen in the nitrogen decreased, the m/z 75 signal increased to 2.0-3.1%. This was accompanied by a concomitant decrease in the m/z 91 signal from 5.2-6.6% to 0.7-1.5%, whereas the signals for [M+H](+) and m/z 237 were essentially unchanged. Signals at m/z 75 with intensities comparable with those observed for the 99.9% pure nitrogen were also obtained for all the arsenosugars when the HPLC/ESI-MS system was operated with a Domnick Hunter Nitrox UHPLCMS18 nitrogen generator. Dimethylarsinic acid, arsenobetaine, trimethylarsine oxide, arsenocholine and the tetramethylarsonium cation also gave no signal at m/z 75 when they were analyzed with the Whatman model 75-72 nitrogen generator, but clear signals at m/z 75 were observed with the Domnick Hunter Nitrox UHPLCMS18 nitrogen generator. A nitrogen quality of at least 99.9% is required to obtain elemental information (m/z 75) when arsenic compounds are investigated by HPLC/ESI-MS. Molecular and elemental information from one chromatographic run is a valuable tool for the characterization of unknown arsenic compounds.

Arsenicals↗
PubMed1987

Nitrogen deficits in aroclor 1254-treated rats.

Nitrogen balance and the efficiency of retaining assimilated dietary nitrogen (biological value) were evaluated in Aroclor 1254-treated (ARO) rats and in vehicle-treated, pair-fed (PF) and ad libitum-fed (AF) rats (150-190 g). ARO-treated rats (300 mg/kg/day, po on 4 consecutive days) lost weight and consumed less chow than the AF group while the weight of the PF rats was not different from those of either the ARO or AF groups. The nitrogen balance and the biological value for the ARO rats were also significantly less than those of the AF rats whereas the PF controls were not different. The ingested calories (expressed in kcal/(kg body wt)0.73) by the ARO and PF rats were equal, but were less than those of the AF group. The ARO and PF groups excreted the same amounts of fecal nitrogen which were less than the fecal nitrogen excretion by the AF rats. The absorbed fraction of the ingested nitrogen was the same among all groups, which indicated that the digestibility and absorption of the dietary nitrogen were not changed. By contrast, the ARO group excreted the same amount of urinary nitrogen and urea as AF rats while the PF group excreted significantly less urinary nitrogen than the latter controls. Thus, the loss of nitrogen by the ARO group was attributed to increased excretion of urinary nitrogen, most likely as urea, in relation to the nitrogen intake. The nitrogen retention and balance in rats with ARO exposure are similar to the response in rats fed a diet of low biological value except that the influence of ARO on nitrogen metabolism occurred during the postabsorption phase.

Amino Acids↗
PubMedDate not supplied

Nitrogen and phosphorus cycling in shrimp ponds and the measures for sustainable management.

Six ponds of age 3 were selected 45 km north from Suzhou in the Tailake region, and research conducted on nitrogen and phosphorus cycling in P. vannanmei (Penaeus vannanme) ponds and M. nipponense (Macrobrachium nipponense) hatchery ponds under normal management. Two treatments each had three replications. The results confirmed that feed was the major path of nitrogen and phosphorus input, each accounted for 61.24% (193.81 kg ha(-1)) and 81.08% (45.20 kg ha(-1)) of the total nitrogen and phosphorus input for P. vannanme ponds; the values for M. nipponense ponds were 43.93% (86.31 kg ha(-1)) and 57.67% (14.61 kg ha(-1)), respectively. Water pumped into ponds contributed on average 83.57 kg ha(-1) nitrogen and 8.48 kg ha(-1) phosphorus for P. vannanmei ponds, and 87.48 kg ha(-1) nitrogen and 7.00 kg ha(-1) phosphorus for M. nipponense hatchery ponds. Shrimp harvest recovered 102.81 kg ha(-1) nitrogen (32.94% of the total nitrogen input) and 7.94 kg ha(-1) phosphorus (14.23% of the total phosphorus input) for P. vannanme ponds; and 43.94 kg ha(-1) nitrogen and 4.46 kg ha(-1) phosphorus for M. nipponense hatchery ponds. The sum of nitrogen losses through volatilization, denitrification and sedimentation was 173.62 and 122.39 kg ha(-1), 54.86% and 62.29% of the total nitrogen input for P. vannanme ponds and M. nipponense hatchery ponds, respectively. Sediment accumulated 41.46 and 14.63 kg ha(-1) phosphorus, 74.37% and 64.85% of the total phosphorus input for P. vannanm ponds and M. nipponense hatchery ponds. Draining and seeping caused 40.06 kg ha(-1) nitrogen (12.66% of total nitrogen input) and 6.36 kg ha(-1) phosphorus (11.40% of total phosphorus input) loss to the surrounding water from P. vannanme ponds in 114 days; 30.14 kg ha(-1) nitrogen (15.34% of the total input) and 4.45 kg ha(-1) phosphorus (17.57% of the total input) to channel water from M. nipponense hatchery ponds in 87 days, respectively. Countermeasures for sustainable pond management include improving feeds and feeding, sediment treatments, machine aerating, chemicals with no pollution, and integrated fish-shrimp cultivation. Management of water resources for pond and methods to reduce nitrogen and phosphorus loading into surrounding water from drainage are elucidated.

Aquaculture↗
PubMed1993

Utilization of non-protein nitrogen in whey-dominant formulae by low-birthweight infants.

1. The effects of increasing non-protein nitrogen intake on nitrogen balance and alpha-amino nitrogen flux rate using [15N]glycine were examined in 30 low-birthweight appropriate-for-gestational-age infants (birthweight 1.5-2.0 kg). The compositions of the three whey-dominant formulae were similar except for the ratios of non-protein nitrogen/protein nitrogen, which were 6.5:93.5, 11.4:88.6 and 17.5:82.5. 2. Infants in the three diet groups each received similar total nitrogen intakes (395 mg of N day-1 kg-1, SD 2.6; n = 3). Protein nitrogen and non-protein nitrogen intakes were different as expected. Energy absorption (449 kJ day-1 kg-1, SD 13; n = 3) did not differ significantly between groups. A similar weight gain was observed in all groups. 3. Nitrogen absorption (76%, SD 4; n = 3) was not significantly different between groups. Apparent urea balance was significantly increased and became positive in the group receiving the formula with the higher proportion of non-protein nitrogen and urea nitrogen. Nitrogen retention, however, was significantly depressed in this group, indicating decreased efficiency of nitrogen utilization at this level of non-protein nitrogen despite an enhanced urea salvage. 4. The enrichment of the 15N label in urinary urea at isotopic steady state was significantly reduced in infants receiving the highest urea-containing formula, presumably due to the dilution of 15N-labelled urea by dietary urea. No difference, however, was found in the enrichment of the 15N label in urinary ammonia. Rates of alpha-amino nitrogen flux, protein synthesis and protein breakdown calculated from the ammonia labelling did not differ significantly between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Caseins↗
PubMed1980

[Influence of various feedstuffs containing fat and protein on the nitrogen metabolism of calves].

Experiments concerning the nitrogen metabolism of 3-, 5-, 7-, 9-, and 11-week-old calves were carried through. The calves were daily fed 146, 219, 323 g milk replacer and differing amounts of dried skim milk (697, 761, 717, 723, 653 g). Energy consumption was dependent on the consumption of milk replacer. With increasing age, N-digestibility and N-retention from the feedstuffs diminished gradually. The smallest decrease of N-retention was observed with those animals receiving the highest amount of milk fat energy. The decrease of nitrogen digestibility can be attributed to the higher consumption of plant feedstuffs and the decrease of the biologic value of the protein. The experiments concerning the nitrogen metabolism show that a higher dosage of fat had a favourable influence on nitrogen retention. At an age of between 7 and 9 weeks correlation coefficients of between +0.50 and +0.36 were ascertained between the fat content of the feed ration and nitrogen retention. At the same age correlation coefficients of +0.60 resp. +0.53 were ascertained between the energy content of the ration and nitrogen retention. These investigations are the basis for the statement that for the nitrogen retention of calves at the age of 7 to 9 weeks feed energy (fat) is the most important factor. A close positive correlation could be observed between the crude protein consumed with the feed ration and the amount of digested nitrogen. Moderately positive correlation coefficients were calculated between the amount of nitrogen taken in resp. the amount of digestible nitrogen and the assessed amount of nitrogen at the age of 7, 9 and 11 weeks. The experiments with the nitrogen metabolism are the basis for the statement that protein and fat together determine the amount of nitrogen retention for calves fed wth moderate milk protein. For calves fed with less milk protein, 23 to 34% fat in the dry matter of the milk replacer proved to be successful. The favourable effect of a higher amount of milk replacer on nitrogen retention can also be attributed to the higher amount of chemotherapeutic sustances (vitamins, antibiotics) taken in with the milk replacer.

Animal Feed↗
PubMedDate not supplied

Free amino acid formula: nitrogen utilization and metabolic effects in normal subjects.

A previous study indicated increased urea production and low nitrogen (N) retention on a free amino acid elemental formula (FAA; Vivonex-HN). The limitations of this earlier study were: irregular nitrogen absorption in the malabsorption patients, high nitrogen intake, and failure to match FAA to control formula (hydrolyzed casein; CAS; Criticare-HN) with respect to kcal/nitrogen. A more critical test of FAA quality was sought in the current study. Four healthy males received the minimal daily nitrogen requirements (0.6 g protein/kg) from either FAA or CAS in a 10-day balance study; a second balance on the alternate formula followed. Maintenance energy, minerals, and vitamins were supplied in each period. The results indicated a higher apparent nitrogen absorption (p less than 0.05) from FAA relative to CAS in the first 5 days of the balance, although these differences were no longer present in the remaining 5 days of the period. Urinary total nitrogen increased on FAA, most of which could be accounted for by urea nitrogen; urinary creatinine nitrogen, ammonia nitrogen, and uric acid nitrogen were nearly identical between formulas. The unmeasured fraction of urinary nitrogen was markedly diminished on FAA while the urea nitrogen to total nitrogen ratio was significantly increased (p less than 0.05) compared to CAS. During the initial 5 days of study nitrogen balance was lower on FAA than on CAS and this difference became significant during the last 5 days of the period (mean +/- SD for FAA = -0.42 +/- 0.59 g/D vs CAS = 0.98 +/- 0.30 g/day, p less than 0.001). Hyperglycinemia was consistently present during FAA infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

The integration of energy and nitrogen balance in the hummingbird Sephanoides sephaniodes.

Floral nectars are rich in energy but contain only traces of amino acids, and it has been hypothesized that arthropods may be an important source of energy and amino acids for hummingbirds. We studied the nitrogen requirements of hummingbirds as well as how they use small arthropods to satisfy their nitrogen and energy requirements and how organ mass varies with nitrogen intake. Non-reproductive green-backed firecrowns Sephanoides sephaniodes were maintained for 10 days on diets containing 0%, 0.96%, 1.82%, 4.11% and 11.1% nitrogen (dry-matter basis). A second group of individuals were fed with varying amounts of nitrogen-free nectar supplemented with fruit flies. Finally, non-reproductive hummingbirds were captured as a control group for analysis of organ mass and size as well as fat content. The maintenance nitrogen requirement of green-backed firecrowns determined by regression was 1.42 mg N day(-1), yet they required nearly 10 mg N day(-1) to maintain body mass. When arthropods were available, we observed that hummingbirds required approximately 150 fruit flies to maintain body mass, which corresponds to a 5% nitrogen diet. Interestingly, when nectar was restricted (to 4 ml day(-1)), or was absent, arthropods alone were not able to satisfy the body mass balance requirements of hummingbirds, suggesting that arthropods are not adequate as an energy source. In the group offered an 11.1% nitrogen diet, the size and surface of the small intestine, and liver and kidney mass increased in comparison with the control group (non-reproductive field hummingbirds) or the nitrogen-free group, suggesting a nitrogen overload. Our results are in agreement with other studies showing low nitrogen requirements by nectarivores. An important point to stress is that nitrogen digestibility declined in the 11.1% nitrogen diet, which strongly supports our nitrogen absorption saturation hypothesis.

Analysis of Variance↗
PubMed2002

Implication of maternal nitrogen balance in the regulation of circulating levels of insulin-like growth factor-I in human pregnancy.

Nutrition plays an important role in regulating the circulating levels of insulin-like growth factor-I (IGF-I). We have demonstrated that reduced nitrogen balance is related to changes in serum IGF-I levels but not serum growth hormone levels in pregnant rats. In the present study, we investigated the effects of changes in nitrogen balance on serum IGF-I levels in normal and malnourished pregnant women (defined as having negative nitrogen balance). Forty-eight pregnant women (threatened miscarriage and premature labor, 39; pre-eclampsia, 3; hyperemesis, 3; ileus, 2; bleeding from the colon, 1) and 19 non-pregnant women admitted in Kobe University Hospital were enrolled in this study. Blood samples of normal pregnant controls were also obtained from 172 healthy pregnant women attending the outpatient clinic. Serum IGF-I levels and nitrogen balance were measured serially in 9 pregnant women with threatened miscarriage and premature labor and 9 malnourished pregnant women out of 48 pregnant women. Serum IGF-I and urinary nitrogen levels were measured by radioimmunoassay with acid-ethanol extraction and the Dumas method, respectively. Nitrogen balance was expressed as the difference between daily nitrogen intake and nitrogen excretion assessed by urinary nitrogen levels. Serum IGF-I levels in normal pregnant controls significantly increased in the third trimester of pregnancy compared with non-pregnant controls. No difference in serum IGF-I levels in any trimester of pregnancy was observed between normal pregnant controls and pregnant women with threatened miscarriage and premature labor. There was no significant difference in nitrogen balance between the pregnant women with threatened miscarriage and premature labor and non-pregnant controls. In the longitudinal study, no correlation was found between the changes in serum IGF-I levels and those in nitrogen balance in the 9 pregnant women with threatened premature labor (daily nitrogen balance > 0 g/day) on the basis of linear regression analysis. On the other hand, the changes in serum IGF-I levels in the 9 malnourished pregnant women were significantly correlated with those in nitrogen balance (y = 1.72x + 17.5; r = 0.60; P < 0.05: linear regression analysis). These results indicate that maternal nutritional states have a major effect on serum IGF-I levels in malnourished pregnant women, but not in pregnant women with daily nitrogen balance > 0 g/day. Serum IGF-I levels can be a potent index of nutritional states under malnutrition during human pregnancy.

Adult↗
PubMed2001

The role of leaf nitrogen content in determining turtlegrass (Thalassia testudinum) grazing by a generalized herbivore in the northeastern Gulf of Mexico.

In shallow marine environments the variability in grazing on seagrasses has been hypothesized to be controlled, in part, by the nutritive quality (i.e., nitrogen content) of their leaves. The few existing studies of the relationship between leaf nitrogen content and seagrass grazing have all found a positive relationship between leaf nitrogen content and preference by selective vertebrate grazers (i.e., the bucktooth parrotfish, green sea turtles, and dugongs). However, most marine herbivores (both vertebrate and invertebrate) are thought to be extreme generalists with broad diets of variable nutritive quality (e.g., detritus, living plants, and animals), suggesting the currently held view on the role leaf nutrient content in explaining the variability of seagrass grazing is an oversimplification.In this study, we evaluated how leaf nitrogen content influenced grazing on turtlegrass by a generalist invertebrate herbivore (the pink sea urchin Lytechinus variegatus) in the northeastern Gulf of Mexico. Using a short-term laboratory test and a longer-term field experiment, we tested the hypothesis that leaf nitrogen content controls sea-urchin grazing on seagrass leaves. We hypothesized that if poor nutritive value of seagrasses is responsible for reduced rates of feeding, then increasing leaf nitrogen concentrations should lead to increased rates of seagrass consumption by sea urchins.In the field experiment, we significantly enriched seagrass leaf nitrogen concentrations (some 10-20% depending on month) in experimental plots with a commercial fertilizer and we manipulated grazing intensity by enclosing adult sea urchins at densities that bracketed the range of average densities observed in the region (i.e., 0, 10 and 20 individuals/m(2)). Comparisons of changes in aboveground seagrass production and biomass showed no evidence that sea urchins grazed significantly more in treatments where leaf nitrogen was enriched. Because the statistical power of our test to detect such differences was low and aboveground seagrass production varied significantly among treatments, we also used a mass balance equation to estimate sea urchin consumption of nitrogen-enriched and unenriched leaves. This showed that sea urchins compensated for low nitrogen levels in our unenriched treatments by eating more leaves than in treatments where leaf nitrogen was elevated. Using a laboratory test, we also found that sea urchins ate less nitrogen-enriched seagrass than unenriched seagrass. In combination, these results show that, in contrast to findings reported for vertebrate herbivores, sea urchins feed at higher rates when offered seagrass leaves of lower leaf nitrogen content, and that low levels of leaf nitrogen are not always an effective defense against herbivores.

Journal Article↗