Measurement Of Nitrogen Content Research Articles

A study on the simultaneous determination of nitrogen content and 15N isotope abundance in plants using peak height intensities at m/z 28 and 29

A method for simultaneous determination of nitrogen content and 15N isotope abundance in plants was established by Elemental analysis-gas isotope ratio mass spectrometry. Taking poplar leaves and l-glutamic acid as standards, nitrogen content was determined using the standard curve established by weighted least squares regression between the mass of nitrogen element and the total peak height intensity at m/z 28 and 29. Then the 15N isotope abundance was calculated with the peak height intensity at m/z 28 and 29. Through the comparison of several sets of experiments, the impact of mass discrimination effect, tin capsule consumables, isotope memory effect, and the quality of nitrogen on the results were assessed. The results showed that with a weight of 1/x2, the standard curve has a coefficient of determination (R2) of 0.9996. Compared to the traditional Kjeldahl method, the measured nitrogen content deviated less than 0.2 %, and the standard deviation (SD) was less than 0.2 %. Compared to the sodium hypobromite method, the 15N isotopic abundances differed less than 0.2 atom%15N, and the SD was less than 0.2 atom% 15N. The established method offers the advantages of being fast, simple, accurate, and high throughput, providing a novel approach for the simultaneous determination of nitrogen content and 15N isotope abundance in plant samples.

An Electrochemical Approach to in-Situ Continuous Soil Nitrate Monitoring

Soil nitrogen is the most limiting nutrient affecting plant growth. However, due to poor soil management due to lack of soil health information, high-N fertilizer use increased exponentially. The UN has labeled nitrogen pollution one of the most important pollution issues facing humanity[1]. Not only does it affect life on land and underwater, it is also 300 times more potent at heating the climate than carbon dioxide while remaining active for 100 years in the atmosphere. Currently, soil nitrogen assessment techniques require destructive sampling where a soil core is collected then shipped to a lab to measure nitrogen content. Not only does this technique have high costs, it only measures nitrogen levels at that specific time point. In this work, we utilized commercially available screen printed electrodes (SPE) with a nitrate ionophore for low cost real-time continuous tracking of soil nitrate levels. The ionophore coating utilizes tetradodecylammonium nitrate (TDDA) as the selective reagent as it’s highly specific to nitrate ions. Previous work done using TDDA used open circuit potential (OCP) to measure nitrate concentration. Soil water content, pH, environmental noise, and other ions impact OCP thus making it unreliable for long term continuous measurements. This work utilizes electrochemical impedance spectroscopy (EIS) instead as it is more robust against the previously mentioned parameters. By opting to use a higher frequency of 1 kHz to extract nitrate concentration, we avoid environmental noise that are dominant at lower frequencies. The sensor output was calibrated in three different soil textures from 2 – 512 ppm presented in Fig. 1(a) for Clay soil. Then the sensor accuracy was validated to the gold standard cadmium reduction method presented in Fig. 1(b) showing non-significant differences with one sample only having a *p-value of 0.049. Lastly, the sensor stability was measured for 7 days continuously in soil with a coefficient of variation of 17% which is under the acceptable standard 20%.Figure 1 (a) Calibrated dose response for Clay soil with 50% water content. (b) vaidation of proposed sensor against gold standard in various soil types. (c) longitudinal study showing stablity and consistency of sensor performance in-situ Figure 1

Optical Properties of Bulk Single-Crystal Diamonds at 80-1200 K by Vibrational Spectroscopic Methods.

Bulk diamonds show great potential for optical applications such as for use in infrared (IR) windows and temperature sensors. The development of optical-grade bulk diamond synthesis techniques has facilitated its extreme applications. Here, two kinds of bulk single-crystal diamonds, a high-pressure and high-temperature (HPHT) diamond and a chemical vapor deposition (CVD) diamond, were evaluated by Raman spectroscopy and Fourier Transform Infra-Red (FTIR) spectroscopy at a range of temperatures from 80 to 1200 K. The results showed that there was no obvious difference between the HPHT diamond and the CVD diamond in terms of XRD and Raman spectroscopy at 300–1200 K. The measured nitrogen content was ~270 and ~0.89 ppm for the HPHT diamond and the CVD diamond, respectively. The moderate nitrogen impurities did not significantly affect the temperature dependence of Raman spectra for temperature-sensing applications. However, the nitrogen impurities greatly influence FTIR spectroscopy and optical transmittance. The CVD diamond showed higher transmittance, up to 71% with only a ~6% drop at temperatures as high as 873 K. This study shows that CVD bulk diamonds can be used for IR windows under harsh environments.

Predicting Canopy Nitrogen Content in Citrus-Trees Using Random Forest Algorithm Associated to Spectral Vegetation Indices from UAV-Imagery

The traditional method of measuring nitrogen content in plants is a time-consuming and labor-intensive task. Spectral vegetation indices extracted from unmanned aerial vehicle (UAV) images and machine learning algorithms have been proved effective in assisting nutritional analysis in plants. Still, this analysis has not considered the combination of spectral indices and machine learning algorithms to predict nitrogen in tree-canopy structures. This paper proposes a new framework to infer the nitrogen content in citrus-tree at a canopy-level using spectral vegetation indices processed with the random forest algorithm. A total of 33 spectral indices were estimated from multispectral images acquired with a UAV-based sensor. Leaf samples were gathered from different planting-fields and the leaf nitrogen content (LNC) was measured in the laboratory, and later converted into the canopy nitrogen content (CNC). To evaluate the robustness of the proposed framework, we compared it with other machine learning algorithms. We used 33,600 citrus trees to evaluate the performance of the machine learning models. The random forest algorithm had higher performance in predicting CNC than all models tested, reaching an R2 of 0.90, MAE of 0.341 g·kg−1 and MSE of 0.307 g·kg−1. We demonstrated that our approach is able to reduce the need for chemical analysis of the leaf tissue and optimizes citrus orchard CNC monitoring.

On the experimental determination of the nitrogen content of thermally upgraded electrical papers

In this paper, the nature of thermally upgraded Kraft electrical insulating papers and their characterization by measurement of nitrogen content is discussed. A historical context and explanation of the basics of the various chemical methods used to measure nitrogen content in electrical papers is presented. The Kjeldahl and Dumas methods for quantifying nitrogen content were compared using six insulating papers in different laboratories in an effort to correlate the results obtained with both techniques. The results provide an insight into the viability of the Dumas combustion method as a proposed industry standard test for measuring the nitrogen content of paper. Moreover, data on the accuracy, reproducibility, and repeatability of the Dumas method is provided for the analysis of thermally upgraded electrical papers.

Nitrogen content determinations in different stages of thermal treatment involved in conversion of ammonium diuranate to uranium metal

Determination of nitrogen content in the uranium metal and uranium oxide based reactor fuels is important to meet the requirement of specifications given by fuel designer. Therefore, a systematic study was carried out to determine the variations in nitrogen content during the conversion of ammonium diuranate (ADU) to uranium oxides (UO3 and UO2), and finally to uranium metal by inert gas fusion-thermal conductivity detection (IGF-TCD) technique. To understand the measured nitrogen content variations, the thermal decomposition study of ADU was carried out using thermogravimetry (TG)/differential thermogravimetry (DTG) and differential thermal analysis (DTA) in the temperature range of 25–1073 K. Powder X–ray diffraction (XRD) technique was used to confirm the formation of uranium oxide precursors at different temperature.

Melamine dependent fluorescence of glutathione protected gold nanoclusters and ratiometric quantification of melamine in commercial cow milk and infant formula

Companies processing the milk for the further production of powdered infant formulation normally check the protein level through a test measuring nitrogen content. The addition of melamine which is a nitrogen-rich organic chemical in milk increases the nitrogen content and therefore enhances its apparent protein content. However, the melamine causes kidney failure and death owing to the formation of kidney stone. Thus the determination of melamine in humans and milk products have gained great significance in recent years. The gold nanoclusters (AuNCs) have attracting features due to its unique electronic and optical properties like fluorescence nature. Therefore one can use AuNCs in the field of biosensor, bio-imaging, nanobiotechnology, drug delivery, diagnosis etc. We report, a new ratiometric nanosensor established for the selective and sensitive detection of melamine based optical sensing using glutathione stabilized AuNCs. The AuNCs were characterized by high-resolution transmission electron microscopy (HR-TEM), UV–visible and Photoluminescence (PL) spectroscopic techniques. In the presence of melamine, the PL intensity at 430nm increases owing to the (turn-on) enhancement in fluorescence, whereas PL intensity at 610nm decreases due to the melamine-induced aggregation and subsequent aggregation-enhanced emission quenching. The observed changes were ascribed to the hydrogen bonding interaction between melamine and AuNCs, which led to the aggregation of the nanoclusters. This was confirmed by dynamic light scattering and HR-TEM measurements. The present probe showed an extreme selectivity towards the determination of 28.2μM melamine in the presence of 100-fold excess of common interfering molecules such as Alanine, Glycine, Glucose, Cystine etc. The proposed method was successfully applied to determine melamine in cow milk.

Heating Has No Effect on the Net Protein Utilisation from Egg Whites in Rats.

Egg whites (EW) are a good source of protein; however, they are typically heated prior to consumption. Therefore, we investigated the effects of different heating conditions on the protein utilisation rate of EW. Male Sprague-Dawley rats (n = 36, 198 ± 1 g) were divided into six groups and fed American Institute of Nutrition-76 chow containing unheated EW, soft-boiled EW, boiled EW, milk whey protein, soybean protein, or no protein over a 10-day period using pair-feeding. Urine and faeces were sampled daily beginning on day 5 to measure nitrogen content and the net protein utilisation (NPU) rate. The soybean protein group had a significantly lower level of food intake and was thus excluded from subsequent analyses. The NPU value was similar among the unheated, soft-boiled, and boiled EW groups (97.5 ± 0.4, 96.5 ± 0.1, and 96.5 ± 0.7, resp.). The EW group values were significantly higher than the whey group values (90.5 ± 1.0). These results show that EW serve as a good source of protein, irrespective of heating.

Materials characterisation by angle-resolved scanning transmission electron microscopy.

Solid-state properties such as strain or chemical composition often leave characteristic fingerprints in the angular dependence of electron scattering. Scanning transmission electron microscopy (STEM) is dedicated to probe scattered intensity with atomic resolution, but it drastically lacks angular resolution. Here we report both a setup to exploit the explicit angular dependence of scattered intensity and applications of angle-resolved STEM to semiconductor nanostructures. Our method is applied to measure nitrogen content and specimen thickness in a GaNxAs1−x layer independently at atomic resolution by evaluating two dedicated angular intervals. We demonstrate contrast formation due to strain and composition in a Si- based metal-oxide semiconductor field effect transistor (MOSFET) with GexSi1−x stressors as a function of the angles used for imaging. To shed light on the validity of current theoretical approaches this data is compared with theory, namely the Rutherford approach and contemporary multislice simulations. Inconsistency is found for the Rutherford model in the whole angular range of 16–255 mrad. Contrary, the multislice simulations are applicable for angles larger than 35 mrad whereas a significant mismatch is observed at lower angles. This limitation of established simulations is discussed particularly on the basis of inelastic scattering.

Analyzing nitrogen in natural and synthetic silicate glasses by secondary ion mass spectrometry

Volatile releases through volcanic eruptions are one of the major processes contributing to the global nitrogen cycle. Past studies have often estimated the magnitude of this flux using volcanic emission measurements, which are limited to currently active systems and sensitive to atmospheric contamination. Another possible approach is the measurement of nitrogen in melt inclusions, which are parcels of magmatic melt trapped prior to eruption. This methodology requires appropriate analytical parameters for nitrogen analysis in silicate glasses by secondary ion mass spectrometry (SIMS), which have not yet been established. To this end, calibrations for nitrogen were obtained using ion implanted basaltic and rhyolitic glasses. We demonstrate that water content significantly affects the ion yields of 14N+ and 14N16O−, as well as the background intensity of 14N+ and 12C+. Application of implant-derived calibrations to natural samples provide the first reported concentrations of nitrogen in melt inclusions. These measurements were made on samples from the Bishop Tuff in California, the Huckleberry Ridge Tuff of the Yellowstone Volcanic Center, and material from the Okaia and Oruanui eruptions in the Taupo Volcanic Center. In studied material, we often find maximum nitrogen contents of less than 45ppm and that nitrogen concentration varies positively with CO2 concentration, which reflects a partial degassing trend. Using the maximum measured nitrogen contents for each eruption, we find that the Bishop released >3.4×1013, the Huckleberry Ridge released >1.4×1014, the Okaia released >1.0×1011, and the Oruanui released >4.5×1013g of nitrogen. Simple calculations suggest that with concentrations such as these, rhyolitic eruptions may ephemerally increase the nitrogen flux to the atmosphere, but are insignificant compared to the 4×1021g of nitrogen stored in the atmosphere.

Autolytic Isolation of Chitin from White Shrimp (Penaues Vannamei) Waste

White shrimp waste comprised of shrimp head, tail and shell contains valuable materials such as chitin, protein, enzymes, minerals, natural pigments, etc. Isolation of chitin from white shrimp waste through an autolysis enzymatic deproteination is described in this paper. The deproteination rate was estimated by measuring nitrogen content during the autolysis and the structure was analyzed by FTIR. The results show that autolysis of white shrimp waste was effectively performed at pH 2 with the highest rate observed in the first two days of autolysis, showing it contains 13.0% protein and 14.7% chitin. The chitin produced after a 9-day autolysis indicated a less clean result than chitin which is chemically digested.

Responses of Ulva prolifera to short-term nutrient enrichment under light and dark conditions

To define responses of short-term nutrient uptake in Ulva prolifera, we measured uptake rates, enzyme activity, and tissue nutrient content in lab experiments where we manipulated nutrient supply and irradiation. Nitrate uptake of U. prolifera was significantly impacted by the external nitrate concentrations, and ammonium uptake was mainly determined by the light availability. The measured nitrogen contents in tissues were higher than the calculated values from the uptake of dissolve inorganic nitrogen, indicating that U. prolifera might use multiple nitrogen sources. High external phosphate concentrations and sufficient light can accelerate the phosphate uptake of U. prolifera, while the measured phosphorus contents in tissues were lower than the calculated values from the uptake of phosphate, suggesting a possibility of internal phosphorus release. The enzymatic activities of nitrate reductase (NR), acid phosphatase (AcP) and alkaline phosphatase (AP) showed little changes, indicating that enzymatic activity might not a direct factor determining the short-term nutrient uptake of U. prolifera.

Determination of lettuce nitrogen content using spectroscopy with efficient wavelength selection and extreme learning machine

Measuring the nitrogen content of plants is useful for nitrogen fertilizer management. The aim of this work is to explore the use of spectroscopy for estimating lettuce leaf nitrogen content. Leaf reflectance spectra were measured using a spectroradiometer with a range of 350–2500 nm, and 160 fresh lettuce leaves given five different nitrogen treatments were used for spectra acquisition and total nitrogen determination. Interval partial least squares (iPLS), synergy interval partial least squares (siPLS), and siPLS combined with genetic algorithms (GA-siPLS) were used to select the optimal intervals or variables. Partial least squares (PLS) and extreme learning machine (ELM) methods were used to develop calibration models. One characteristic wavelength region (470–590 nm) using 120 variables was selected by iPLS; four characteristic wavelength regions (440–530, 530–620, 620–710 and 890–980 nm) using 362 variables were selected by siPLS, and 56 wavelength variables were selected by GA-siPLS. Six different regression models were established for nitrogen content by PLS and ELM based on optimal intervals or variables. The results imply that GA-siPLS is an efficient variable selection algorithm and ELM is a successful nonlinear regression tool. Furthermore, GA-siPLS combined with ELM is a feasible method for measuring nitrogen content in lettuce, as it performed better than other models. The optimal results achieved a root mean square error of prediction (RMSEP) = 0.2890% and correlation coefficient Rp = 0.9218.

Nitrogen distribution between aqueous fluids and silicate melts

The partitioning of nitrogen between hydrous fluids and haplogranitic, basaltic, or albitic melts was studied at 1–15 kbar, 800–1200 °C, and oxygen fugacities (fO2) ranging from the Fe–FeO buffer to 3log units above the Ni–NiO buffer. The nitrogen contents in quenched glasses were analyzed either by electron microprobe or by secondary ion mass spectrometry (SIMS), whereas the nitrogen contents in fluids were determined by mass balance. The results show that the nitrogen content in silicate melt increases with increasing nitrogen content in the coexisting fluid at given temperature, pressure, and fO2. Raman spectra of the silicate glasses suggest that nitrogen species change from molecular N2 in oxidized silicate melt to molecular ammonia (NH3) or the ammonium ion (NH4+) in reduced silicate melt, and the normalized Raman band intensities of the nitrogen species linearly correlate with the measured nitrogen content in silicate melt. Elevated nitrogen contents in silicate melts are observed at reduced conditions and are attributed to the dissolution of NH3/NH4+. Measured fluid/melt partition coefficients for nitrogen (DNfluid/melt) range from 60 for reduced haplogranitic melts to about 10 000 for oxidized basaltic melts, with fO2 and to a lesser extent melt composition being the most important parameters controlling the partitioning of nitrogen. Pressure appears to have only a minor effect on DNfluid/melt in the range of conditions studied. Our data imply that degassing of nitrogen from both mid-ocean ridge basalts and arc magmas is very efficient, and predicted nitrogen abundances in volcanic gases match well with observations. Our data also confirm that nitrogen degassing at present magma production rates is insufficient to accumulate the atmosphere. Most of the nitrogen in the atmosphere must have degassed very early in Earth's history and degassing was probably enhanced by the oxidation of the mantle.

Beshtauite, (NH4)2(UO2)(SO4)2{middle dot}2H2O, a new mineral from Mount Beshtau, Northern Caucasus, Russia

A new mineral beshtauite, (NH 4 ) 2 (UO 2 )(SO 4 ) 2 ·2H 2 O, was found in the oxidation zone of the Beshtau uranium deposit, Mount Beshtau, Stavropol region, Northern Caucasus, Russia, and named after the locality. It is associated with rozenite, gypsum, lermontovite, and older marcasite, pyrite, halloysite, and opal. Beshtauite occurs as well-shaped short-prismatic crystals up to 0.1 × 0.15 × 0.2 mm, their clusters and crusts up to 0.5 mm across growing on marcasite. Beshtauite is transparent, light green. The luster is vitreous. The mineral fluoresces strongly yellow-green under both short- and long-wave UV irradiation. It is brittle. The Mohs hardness is ca. 2. Cleavage was not observed. D calc is 3.046 g/cm 3 . Beshtauite is optically biaxial (+), α = 1.566(3), β = 1.566(3), γ = 1.592(3), 2 V meas 2 O by difference) is: (NH 4 ) 2 O 10.33, UO 3 53.21, SO 3 29.40, H 2 O calc 7.06, total 100.00. Content of (NH 4 ) 2 O was calculated from measured nitrogen content: 5.56 wt% N. The empirical formula, calculated on the basis of 12 O apfu, is (NH 4 ) 2.12 U 0.99 S 1.96 O 9.91 (H 2 O) 2.09 . Beshtauite is monoclinic, P 2 1 / c , a = 7.7360(8), b = 7.3712(5), c = 20.856(2) A, β = 102.123(8)°, V = 1162.76(19) A 3 , Z = 4 (from single-crystal X-ray diffraction data). The strongest reflections of the X-ray powder pattern [ d (A), I ( hkl )] are: 6.86, 100(011, 102); 5.997, 19(012); 5.558, 15(102); 5.307, 36(111,110); 5.005, 35(013,112); 3.410, 38(114,204,106); 3.081, 24(016); 2.881, 20(106,123). The crystal structure was solved by direct methods and refined on the basis of 2677 independent reflections with I > 4σ( I ) to R 1 = 0.093. The structure is based upon [UO 2 (SO 4 ) 2 (H 2 O)] 2− layers consisting of corner-sharing UO 6 (H 2 O) pentagonal bipyramids and SO 4 tetrahedra. The layers are coplanar to (102) and are linked via hydrogen bonding that involve interlayer NH 4 + ions and H 2 O molecules. Beshtauite is important indicator mineral: its presence can be considered as an evidence of transportation of U 6+ in nature in forms of mobile complexes of uranyl cation with ammonia or polyamines.

Thermodynamics and Dynamics of Nitrogen Increasing in LF Refining Process

Nitrogen is one of harmful elements in liquid steel. Reducing nitrogen quantity is required for making high-grade steel. This paper analyzes the reaction mechanism of nitrogen increasing through the methods of metallurgical thermodynamics and dynamics. In liquid steel dissolved nitrogen and nitrides are the main forms of nitrogen. The factors of influence on nitrogen increasing are temperature, kinds and quantity of the alloying elements in the liquid steel, , the lifetime of foam in foam slag, the quantity of flow of argon and so on. Analytical results of metallurgical thermodynamics and dynamics are verified by measuring nitrogen content in the links of LF refining process of new developed area of Chongqing steel and iron Co.Ltd.

Critical investigation of high temperature gas nitriding of a PM tool steel

AbstractThe nitrogen uptake of high-alloyed steels, especially tool steels, from gaseous atmospheres at elevated temperatures is a well known effect. Besides, for instance, the nitrogenbased case hardening, one application arises in the field of powder metallurgy. Here, introducing nitrogen containing atmospheres during sintering of high-alloyed powder metallurgically produced tool steels could lead to an optimization of the sintering process and an improvement of the materials properties. In this context, several works deal with the application of computational thermodynamics for considering the nitrogen uptake. The scope of this contribution is to investigate in detail the agreement of calculated and experimentally found nitrogen contents. Therefore, one typical gas-atomized powder of a ledeburitic cold work steel was sintered at a temperature of 1230°C, varying the nitrogen partial pressure during sintering between 0.02 MPa and 0.2 MPa. The measured nitrogen contents are compared with values obtained from equilibrium calculations. Additionally, the distribution of nitrogen in the microstructure is investigated by time-resolved optical emission spectrometry and energy dispersive X-ray spectrometry measurements. The results exhibit good agreement between calculated and measured values for low partial pressures of less than 0.1 MPa and an increasing deviation for higher partial pressures. Furthermore, the transformation of vanadium-containing MC carbides to M(C, N) carbonitrides was verified.

A comparative X‐ray photoelectron spectroscopy and medium‐energy ion‐scattering study of ultra‐thin, Hf‐based high‐k films

AbstractUltra‐thin high‐k layers based on HfO2, or Hf‐silicates in combination with sub‐nanometer SiO2, show much promise in their use as Si‐compatible gate dielectrics. XPS has been applied on a range of HfO2/SiO2 and HfSiOx(60%Hf)/SiO2 films on Si(100), before and after decoupled plasma nitridation (DPN) at 1073 K. The treatment of the data was optimized in order to determine individual layer thicknesses of the multilayer stack taking into account the measured nitrogen content of the nitrided films. The procedure adhered to the prescriptions of ISO18118:2004(E) for the calculations of inelastic mean free paths (IMFP) and elastic corrections thereof, using film material properties, like densities and band gaps. Effective attenuation lengths (EAL) were taken throughout as 90% of the respective IMFP, whereas an appropriate set of empirical relative sensitivity factors (RSF) was used. The XPS‐derived thicknesses were compared with corresponding values obtained from medium‐energy ion scattering (MEIS) measurements on the same series of specimens in combination with energy spectrum simulation to provide quantitative layer information with sub‐nanometer resolution. The XPS and MEIS results exhibit very good agreement on the deduced layer structures within the respective experimental uncertainty, and both sets are consistent with the grown nominal layer parameters of the high‐k nanofilms. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of Whey and Fortified Collagen Hydrolysate Protein Supplements on Nitrogen Balance and Body Composition in Older Women

Many elderly people have a low intake of dietary protein, yet their protein requirement may be higher than the current Recommended Dietary Allowance. High-quality protein supplements may be useful to enhance nitrogen retention and increase the availability of essential amino acids in elderly people. We compared the nitrogen balance of two protein supplements (Resource Beneprotein Instant Protein Powder, Nestlé HealthCare Nutrition, Minnetonka, MN, a whey protein concentrate; or Pro-Stat 101, Medical Nutrition USA, Englewood, NJ, a concentrated, fortified, collagen protein hydrolysate) varying in type but not amount of protein content using a crossover study design. The study consisted of two 15-day diet trials separated by a ≥1-week washout period. Nine healthy elderly women (age 71±1 years) were provided a eucaloric diet containing approximately the protein Recommended Dietary Allowance of 0.8 g/kg body weight/day. The supplements constituted about half of the total protein provided to each subject. Nitrogen balance responses were assessed over days 6 to 10 and days 11 to 14 of each trial. Measured nitrogen content of the foods indicated that subjects consumed 0.81±0.02 g protein/kg/day and 0.85±0.05 g/kg/day for the whey and fortified collagen protein trials, respectively. Body weight decreased ( P=0.02) after consumption of the whey supplement, with no significant changes in body weight or composition resulting from the consumption of the collagen supplement. Nitrogen excretion was higher during the whey supplement trial than during the collagen trial ( P=0.047). Therefore, a concentrated, fortified, hydrolyzed collagen protein supplement maintained nitrogen balance and preserved lean body mass during 15 days of consumption of a relatively low-protein diet.

Crude protein changes on grassland along a degradation gradient in a semi-arid climate

The aim with this investigation was to quantify the impact of different veld condition classes, viz. poor, moderate and good on soil-water utilization (SWU: crude protein produced per unit of evapotranspiration), during four growing seasons (2000/01 – 2003/2004). Evapotranspiration was determined by quantifying the soil-water balance equation with the aid of runoff plots and soil-water content measurements. Crude protein (CP) content was calculated from measured nitrogen content (Kjeldahl method) of the leaves, stems and seed. Although the monthly CP concentration (g/kg) of grassland in poor condition was generally higher than that of grassland in good condition, CP production decreased significantly with veld degradation when expressed as total quantity (kg/ha) of dry matter produced. Grassland in good, moderate and poor condition produced on average over the season 141, 97 and 32 kg CP/ha, respectively. Both monthly and seasonal SWU declined significantly with grassland degradation. Grassland in good condition averaged a SWU of 0.32 kg CP/ha/mm during the four growing seasons, compared to the only 0.09 kg CP/ha/mm produced from veld in poor condition. The study shows that it is important to keep grassland in optimal condition to utilize limited soil water for sustainable plant and therefore animal production. Keywords: Crude protein; evapotranspiration; soil-water content; soil-water utilization; veld condition South African Journal of Animal Science Vol. 36 (5) 2006: pp.34-37