Urea N Research Articles

Soil-plant micronutrients dynamics in response to integrated fertilization under wheat–soybean cropping system at Rawalakot, Pakistan

ABSTRACTThis study provided an insight on improving soil-plant micronutrients availability in response to poultry manure (PM), wheat milling residues (WMR) and urea N (UN) and their integration in wheat–soybean cropping system. The treatments were: control; poultry manure full, PM100; wheat milling residues full, WMR100; urea N full, UN100; PM half and WMR half, PM50+WMR50; UN50+PM50; UN50+WMR50; UN50+PM25+WMR25. All amendments were added at the rate or equivalent to 100 kg total N ha–1. Results indicated that the integrated treatments increased Cu, Fe, Mn and Zn uptake of wheat by 35.7–103%, 48.4–111.1%, 85.2–267.0% and 33.8–128.2%, respectively over control. In soybean the corresponding increase in micronutrient uptake (Cu, Fe, Mn and Zn) was 18.3–60.3%, 27.5–87.4%, 14.1–54.6% and 13.2–58.0% in integrated treatments. The post-harvest soil analysis indicated 2 to 3-fold increase in micronutrient content with highest values in PM100 i.e., 2.66 mg kg−1 for Cu, 14.41 mg kg−1 for Fe, 18.58 mg kg−1 for Mn and 2.44 mg kg−1 for Zn, respectively. The results showed that the PM either alone or in integrated with WMR and UN can be an effective management strategy for improving micronutrient content of soil–plant.

Nitrogen Mineralization of a Loam Soil Supplemented with Organic-Inorganic Amendments under Laboratory Incubation.

The quantification of nitrogen (N) supplying capacity of organic amendments applied to a soil is of immense importance to examine synchronization, N release capacity, and fertilizer values of these added materials. The aims of the present study was to determine the potential N mineralization and subsequent nitrification of separate and combined use of poultry manure (PM), wheat straw residues (WSR), and urea N (UN) applied to a loam soil incubated periodically over 140 days period. In addition, changes in total soil N and carbon contents were also monitored during the study. Treatments included: PM100, WSR100, PM50 + WSR50, UN100, UN50 + PM50, UN50 + WSR50, UN50 + PM25 + WSR25, and a control (unfertilized). All the amendments were applied on an N-equivalent basis at the rate of 200 mg N kg-1. Results indicated that a substantial quantity of N had been released from the added amendments into the soil mineral pool and the net cumulative N mineralized varied between 39 and 147 mg N kg-1, lowest in the WSR and highest in the UN50 + PM50. Significant differences were observed among the amendments and the net mineral N derived from a separate and combined use of PM was greater than the other treatments. The net cumulative N nitrified (NCNN) varied between 16 and 126 mg kg-1, highest in UN50 + PM50 treatment. On average, percentage conversion of added N into available N by different amendments varied between 21 and 80%, while conversion of applied N into NO3-–N ranged between 9 and 65%, and the treatment UN50 + PM50 displayed the highest N recovery. Urea N when applied alone showed disappearance of 37% N (N unaccounted for) at the end while application of PM and WSR with UN reduced N disappearance and increased N retention in the mineral pool for a longer period. Organic amendments alone or in combination with UN improved organic matter buildup and increased soil N concentration. These results demonstrate the existence of substantial amounts of N reserves present in PM and WSR that can be utilized efficiently and effectively as potential N source for the management of nutrient poor soils and plant growth.

Soybean Response to Single or Mixed Soil Amendments in Kashmir, Pakistan

The application of animal‐ and plant‐derived organic substrates with minimal additions of commercial N fertilizers is an important management strategy for sustainable agriculture production systems in mountain upland soils subjected to continuous erosion. A 3‐yr (2009, 2010, and 2011) field experiment was conducted to evaluate the effects of separate and combined use of poultry manure (PM), wheat (Triticum aestivum L.) milling residues (WMR), and urea N (UN) on the productivity and N2 fixation of rainfed soybean [Glycine max (L.) Merr.] grown in the Himalayan region of Rawalakot Azad Jammu and Kashmir, Pakistan. The experiment was conducted in a randomized complete block design with three replications. Treatments included UN100, PM100, WMR100, PM50 + WMR50, UN50 + PM50, UN50 + WMR50, UN50 + PM25 + WMR25, and an unfertilized control. Nitrogen from all amendments was applied at an equivalent rate of 100 kg total N ha−1. Compared with the control and UN100 treatments, the organic amendments applied alone or combined with UN significantly increased the number and mass of root nodules and N2 fixation by 36 to 68, 26 to 62, and 8 to 31%, respectively. Poultry manure (PM100) displayed the highest nodulation (49 and 129 nodules) and N2 fixation (43 and 73 kg N ha−1), while UN100 did not differ from the control. Yield and yield components (residue dry matter yield and seed yield) and N use efficiency in the combined treatment UN50 + PM50 was comparable to that recorded under the UN100 treatment. There was a positive correlation between nodule number and mass with N2 fixation (r = 0.86 and 0.79), suggesting that root nodulation can be used as an indicator for N2 fixation. Results of this study confirmed the beneficial effects of organic amendments on N2 fixation and in combination with UN represents a successful and sustainable management strategy for soybean production in mountainous ecosystems.

Improvements in the physical and chemical characteristics of degraded soils supplemented with organic–inorganic amendments in the Himalayan region of Kashmir, Pakistan

Efficient use of organic amendments and changing cropping pattern are important management strategies for restoring the degraded upland soils of Himalayan region. This study was conducted to determine the quantitative effect of poultry manure (PM) and wheat straw residues (WSR) repetitively applied alone or in combination with urea N (UN) on physical and chemical properties of soil under wheat–soybean cropping sequence over three years (2008–09, 2009–10, 2010–11). Treatments included PM100, WSR100, PM50+WSR50, UN100, UN50+PM50, UN50+WSR50, UN50+PM25+WSR25 and a control. Added amendments were applied on N equivalent basis at the rate of 100kgNha−1. Results indicated that organic amendments applied alone or in combination with UN significantly improved soil physical characteristics by lowering bulk density 7–12%, penetration resistance 3–4% and increasing hydraulic conductivity 15–32%, and aggregate stability 13–35%. Application of UN100 alone was ineffective in improving any of these characteristics. Combination of organic–inorganic amendments increased soil organic matter content by 3–9%, total N 14–29%, available P 5–35% and extractable K 12–39%. Response of micronutrient to organic or organic–inorganic amendments was even higher than that recorded for macronutrients. Organic amendments increased soil pH while UN displayed acidifying effect. The C sequestration and nutrient pool of the soil amended with WSR remained rich over PM even though PM contains a lot more nutrients. The study clearly demonstrated that organic amendments applied alone or combined with UN improved the physical characteristic and fertility status of the soils and may be considered as a useful management strategy for restoration of degraded soils in the mountain ecosystem of the Himalayan region of Kashmir, Pakistan.

Chemical composition, intake, ruminal fermentation, plasma metabolites and hormones in range steers

The objective of this study was to determine and compare, seasonally, across two consecutive years the chemical composition, intake, ruminal fermentation and plasma concentrations of glucose (G), urea-N (UN), non-esterified fatty acids (NEFA) and insulin in grazing steers. Data were analysed as repeated measures within a split plot design. The crude protein (CP), metabolisable protein (MP), neutral detergent fibre (NDF) and metabolisable energy (ME) were different within years and seasons (P<0.05). The values for organic matter intake (OMI), CP intake (CPI) and metabolisable protein intake (MPI) were greater in wet season (P<0.01). The pH values were not affected by years and seasons (P > 0.05). Ruminal ammonia (NH3–N) and volatile fatty acid (VFA) concentrations were lower during dry season than during wet season (P < 0.05). The plasma concentrations of G, UN, and insulin were higher in the wet season (P<0.05); however, the NEFA concentrations were higher in the dry season (P<0.05). The variables corresponding to chemical composition, intake, ruminal fermentation and concentrations of metabolites and hormones were affected over time by the years and seasons.

Synergistic effects of biofertilizer with organic and chemical N sources in improving soil nutrient status and increasing growth and yield of wheat grown under greenhouse conditions

Biofertilizers have been identified as value-added soil amendments for improving efficiency of applied fertilizers and increasing soil fertility and crop productivity in sustainable farming system. This study explored the effect of biofertilizer (a mixture of Pseudomonas, Azospirrillium and Agrobacterium strains) supplemented with organic and mineral N fertilizers on soil properties, yield, and NPK uptake of wheat (Triticum aestivum L.) grown under greenhouse conditions. The treatments included the application of fertilizer alone or in different combinations with urea N (UN) and/or poultry manure (PM) added at various strengths. Results indicated that most of the growth characteristics were higher in treatments receiving biofertilizer supplemented with ½UN and full PM (200 mg N kg−1). However, treatments under full recommended N (200 mg N kg−1) or ½UN+full PM had similar effects. Chlorophyll contents were highest in the full UN treatment, followed by the treatment with ½UN+fullPM+biofertilizer. The latter significantly increased the yield and yield components of wheat compared to full UN and exhibited superiority over PM. Similarly, NPK uptake in plant shoot was highest in ½UN+full PM+biofertilizer compared to full UN or full PM treatments. Furthermore, our results showed that biofertilizer supplemented with PM improved soil properties, such as organic matter, NPK content and concentration of the micronutrients Fe, Mn, Cu and Zn. The application of biofertilizer increased the efficiency of both organic and mineral N fertilizer but alone was ineffective in increasing yield. Thus, biofertilizers could be used as value-added soil amendments by supplementing organic and low chemical fertilizer rates for improving soil fertility and sustaining crop productivity.

Effects of small ruminant type and restricted protein intake on metabolism

Boer goat (BG), Spanish goat (SG), and Rambouillet sheep (RS) wethers, ≥2yr of age, were used in a crossover experiment with 28-day periods. Diets were ad libitum consumption of wheat straw alone (CON) or with a 90% soybean meal, 10% molasses supplement given at 0.22% BW (SBM). Initial BW was 35, 55, and 32kg for BG, RS, and SG, respectively. NDF digestibility was similar among animal types and between diets. BW change tended to be lowest for RS (−92, −158, and −107g/day for BG, RS, and SG, respectively; SE=22.6). ME intake was similar among animal types (244, 230, and 259kJ/kg BW0.75 for BG, RS, and SG, respectively; SE=16.6) and greater (P<0.05) for SBM vs. CON (320 vs. 168kJ/kg BW0.75). Total energy expenditure (EE) was greater (P<0.05) for RS than for BG (362, 415, and 402kJ/kg BW0.75 for BG, RS, and SG, respectively) and for SBM vs. CON (413 vs. 374kJ/kg BW0.75). EE by the portal-drained viscera (PDV) (1.34, 1.33, and 1.17MJ/day; SE=0.122) and liver (1.48, 1.44, and 1.32MJ/day; SE=0.133) was similar among animal types. Liver EE was greater (P<0.05) for SBM vs. CON (1.60 vs. 1.22MJ/day), but PDV EE was similar between diets. Net fluxes of ammonia N (AMN) and urea N (UN) across the PDV (AMN: 3.4, 2.4, and 3.2g/day (SE=0.69); UN: −5.2, −3.3, and −4.6g/day (SE=1.19)) and liver (AMN: −3.6, −3.2, and −4.3g/day (SE=0.78); UN: 7.6, 4.8, and 4.2g/day for BG, RS, and SG, respectively (SE=1.17)) were similar among animal types. In conclusion, the magnitude of any difference in N recycling among animal types was less than necessary to affect fiber digestibility. Nonetheless, some findings suggest a lesser ability of sheep to modify metabolic functions to cope with limited nutritional planes elicited by feeding crop residue-based diets, perhaps relating to metabolism by extra-splanchnic tissues.

Effect of Azadirachta indica (neem), sodium thiosulphate and calcium chloride on changes in nitrogen transformations and inhibition of nitrification in soil incubated under laboratory conditions

A laboratory experiment was conducted to examine the effects of nitrification inhibitors (NIs) neem seedcake (Azadirachta indica) (NSC), sodium thiosulphate (Na2S2O3) and calcium chloride (CaCl2) on changes in NH4+–N, inhibition of nitrification and recovery of applied nitrogen (N) in soil. Surface soil samples of 0–15cm were collected from an arable field, amended with urea N (UN) at the rate 200mgNkg−1, UN+NSC, UN+Na2S2O3 and UN+CaCl2 and incubated at 22°C periodically over 50d. Soil without any amendment was used as check (control). Results indicated that more than 58% of N applied as NH4- disappeared over a period of 50d from the soil mineral-N pool. Some of this N (21%) was accumulated as NO3-–N while the remaining N was unaccounted for. Addition of nitrification inhibitors NSC, Na2S2O3, and CaCl2 resulted in a decrease in the extent of NH4+ disappearance by 35%, 44% and 30%, respectively. In the treatment receiving UN alone, 56mg NO3-–Nkg-1 was accumulated over 50d (maximum 93mgkg−1) indicated an active nitrification. Application of nitrification inhibitors NSC, Na2S2O3, and CaCl2 with UN inhibited nitrification by 54%, 64%, and 59%, respectively. Apparent N recovery (ANR) in the treatment receiving UN alone was 63% that substantially increased to 83%, 89% and 76% in the treatments receiving UN+NSC, UN+Na2S2O3, and UN+CaCl2, respectively indicating 32%, 41% and 20% increase in N recovery. Among three NIs tested, Na2S2O3 proved superior in inhibiting nitrification and increasing ANR. The study demonstrated that application of NSC, Na2S2O3, and CaCl2 which are cheap and easily available NIs inhibited nitrification and improved N recovery efficiency of applied N in an arable soil very effectively. It is suggested that these inhibitors should be tested under field conditions for increasing NUE and improving crop productivity.

COMPARATIVE EFFECTIVENESS OF UREA N, POULTRY MANURE AND THEIR COMBINATION IN CHANGING SOIL PROPERTIES AND MAIZE PRODUCTIVITY UNDER RAINFED CONDITIONS IN NORTHEAST PAKISTAN

SUMMARYA field experiment was conducted to evaluate the comparative effectiveness of poultry manure, urea N and the integrated use of both in changing soil properties, nutrient uptake, yield and yield attributes of maize grown at Rawalakot, Azad Jammu and Kashmir, Pakistan. Treatments include control without any amendment (N0); urea N (UN) = 120 kg N ha−1 (N120U); UN = 150 kg N ha−1(N150U); poultry manure (PM) = 120 kg N ha−1(N120PM); PM = 150 kg N ha−1(N150PM); UN = 90 kg N ha−1+ PM = 30 kg N ha−1(N90U+30PM); UN = 60 kg N ha−1+ PM = 60 kg N ha−1(N60U+60PM); UN = 30 kg N ha−1+ PM = 90 kg N ha−1(N30U+90PM). N fertilization from different sources and combinations increased dry matter yield from 5206 kg ha−1 in the control to 5605–5783 kg ha−1 and grain yield increased from 1911 kg ha−1 to 2065–3763 kg ha−1. Application of the highest rate of urea N recorded the highest grain yields of 3763 kg ha−1, double the control. The proportional increase for N90U+30PM and N60U+60PM was 85 and 83% while PM alone gave lower yields (41 and 44%) than the respective urea N treatments. Integrated use of urea + PM proved superior to other treatments in enhancing the uptake of N, P and K in plants. Averaged across two years, uptake of N, P and K in N90U+30PM and N60U+60PM was 88 and 85, 16.5 and 17.5, and 48.5 and 53.5 kg ha−1, respectively compared to 52.5, 11.5 and 33.5 kg ha−1 in the control. Nitrogen use efficiency (NUE) varied from 29% in PM treatments to 30–39% in combined treatments while NUE of 40% was recorded for urea N treatments. Application of PM lowered soil bulk density from 1.19 t m−3 in the control to 1.10 and 1.05 t m−3 in N120PM and N150U, enhanced pH from 7.39 to 7.65 and 7.78 and increased soil organic matter (22 and 32%), total N (21 and 26%), available P (44 and 55%) and available K (10 and 15%) compared with the control. Economic analysis suggested the use of 50% recommended mineral N (60 kg N ha−1) with PM saves the mineral N fertilizer by almost 50% compared to a system with only mineral N application. In addition, increase in N efficiency, plant nutrition and soil fertility associated with combined treatment would help to minimize the use of high cost synthetic mineral fertilizers and represents an environmentally and agronomically sound management strategy.

Calculated nitrogen balance in hemodialysis patients: Influence of protein intake

Optimal nutrient intake is important in the maintenance of a positive nitrogen balance in hemodialysis (HD) patients. The objectives of this study were (1) to assess the influence of two levels of protein intakes on nitrogen balance in stable adult HD patients, and (2) to identify a minimum level of protein intake that would result in a negative nitrogen balance, so that preliminary recommendations may be made in Indian patients on maintenance HD (MHD). Stable, adult, nondiabetic MHD patients were recruited after informed consent into a cross over trial with a high-protein (HP) diet [1.2 g/kg ideal body weight (IBW)/day), followed by a low-protein (LP) diet (0.6 g/kg IBW/day] after appropriate periods of equilibration; for both diets, 50% of protein was of high biological value, and calorie intake was 35 kCal/kg IBW/day. Duplicate meals and residues were weighed, homogenized, and stored at -20 degrees C for analysis of dietary N by the Kjeldahl method, used to check the consistency of the N content of the diet supplied. Pre- and post- (30-minute equilibrated) blood urea samples were drawn, and details of weights and other HD parameters were recorded. Interdialytic urine collections for urea were obtained. N input came from dietary protein calculated as 16% of the weight of biological protein; N output was calculated using blood-side urea measurements and urinary urea excretion and was the sum of urea N (UN) and nonurea N (NUN) losses (assumed to be equal to 0.031 g N/kg/day). Fifteen patients were recruited. Twelve patients completed both limbs of the study. The mean age was 30.3 +/- 12.7 years. The body mass index was 18.9 +/- 2.4. Serum albumin was 3.8 +/- 0.35 g/dL, and Kt/V (equilibrated) was 1.17 +/- 0.3 g/dL. Protein consumed was 1.06 +/- 0.18 g/kg IBW/day in the HP limb versus 0.61 +/- 0.1 g/kg IBW/day in the LP limb (P = 0.000). Energy intake was 33 +/- 6.5 vs. 32.8 +/- 6. 7 kCal/kg IBW/day, respectively (P = 0.8). The normalized protein N appearance (nPNA) was 0.88 +/- 0.2 g/kg/day in the HP limb versus 0. 78 +/- 0.2 g/kg/day in the LP limb (P = 0.02). Dietary N was 73.5 +/- 15.3 g in the HP week and 42.5 +/- 7.5 g in the LP week (P = 0. 000). The difference between this and the sum of (UN + NUN) losses over the week was 29 +/- 13.2 g versus 1.2 +/- 8.1 g, respectively (P = 0.001), showing a strong, uniformly positive nitrogen balance with HP diet and neutral to negative nitrogen balance with LP diet. The ratio of dietary protein intake (DPI) to nPNA was significantly lower (anabolic) in the HP limb (0.7 +/- 0.2 vs. 1.12 +/- 0.3, P = 0. 000). On a scatter plot of nPNA to DPI, a catabolic relationship was demonstrated below a DPI of 0.75 g/kg/day (95% CI, 0.65 to 0.85 g/kg/day). A DPI of approximately 1.1 g/kg/day produces a positive nitrogen balance and 0.6 g/kg/day a neutral to negative nitrogen balance, demonstrating protein anabolism as a function of protein intake. It is suggested that a protein intake of 0.85 g/kg/day should be considered unsafe. These conclusions apply in stable nondiabetic adult HD patients in the setting of adequate dialysis and adequate calorie intake.

Splanchnic nitrogen metabolism by growing beef steers fed diets containing sorghum grain flaked at different densities.

The objective of this study was to determine effects of processing method, dry-rolled (DR) vs steam-flaked (SF), and degree of processing (flake density, FD) of SF sorghum grain on splanchnic (gut and liver) N metabolism by growing steers. Diets contained 77% sorghum grain either DR or SF at densities of 437, 360, and 283 g/L (SF34, SF28, and SF22, respectively). Eight crossbred steers (340 kg initial BW), implanted with indwelling catheters into portal, hepatic, and mesenteric veins and the mesenteric artery, were used in a randomized complete block design. Blood flows and net output or uptake of ammonia N, urea N (UN), and alpha-amino N (AAN) were measured across portal-drained viscera, hepatic, and splanchnic tissues. Plasma arterial, portal, and hepatic concentrations of individual amino acids were also measured. Decreasing FD linearly increased (P = .04) net absorption of AAN (51, 73, and 78 g/d for SF34, SF28, and SF22, respectively) and transfer (cycling) of blood UN to the gut (49, 48 and 64 g/d; P = .02). Net UN cycling averaged 38% of N intake across all diets. Hepatic uptake of AAN or UN synthesis, and splanchnic output of AAN and UN, were not altered by FD. Lowering FD linearly increased (P < or = .02) portal-arterial concentration differences for blood AAN and UN and plasma arterial concentrations for alanine. Steers fed SF compared to DR tended to have greater (P = .11) blood UN cycling (percentage of hepatic synthesis; 64 vs 50%) and decreased (P = .03) net splanchnic UN output (30 vs 50 g/d), but other net fluxes of N were not altered across splanchnic tissues. Steam-flaking compared to dry-rolling tended to decrease (P = .12) portal, but not hepatic, blood flow and increased (P < .01) hepatic-arterial concentration differences for blood UN. Except for a decrease (P = .01) in hepatic-arterial concentration differences of glutamine, plasma amino acid concentrations were not altered by feeding SF vs DR sorghum. Processing method (steam-flaking vs dry-rolling) or increasing the degree of processing (by decreasing FD) of SF sorghum grain resulted in greater transfer of blood UN to the gut. Reducing FD also linearly increased the absorption of AAN by growing steers, which explains (in part) published responses of superior performance by steers fed SF grains.

Effects of processing and storage on the measurement of nitrogenous compounds in ovine blood

Four experiments were conducted to evaluate effects of processing and storage of sheep blood samples on measurements of ammonia N (AMN), urea N (URN), total protein (TP), albumin (ALB), total globulin (GLB), and the non-albumin non-globulin protein fraction (NAG). Experiment 1 compared the effects of using different anticoagulants. Blood samples ( n = 15) were collected via jugular venipuncture into one of four evacuated tubes: no anticoagulant, serum; sodium heparin, plasma; sodium fluoride and potassium oxalate, plasma; tripotassium-ethylenediaminetetraacetic acid (EDTA), plasma. Anticoagulant affected ( P < 0.0001) metabolite values, with TP, ALB, and GLB being higher in heparinized plasma, and URN, NAG, and AMN highest in serum. In addition, blood packed-cell volume was 12% and 15% higher ( P < 0.0001) in samples collected in heparin and EDTA compared with samples collected in sodium fluoride and potassium oxalate. Experiment 2 investigated the effects of repetitive freezing and thawing (0–3 thaw cycles) of plasma samples ( n = 15 blood samples collected in tubes containing sodium fluoride and potassium oxalate). Repetitive freezing and thawing decreased ( P < 0.0001) URN and NAG by 21% and 54%, respectively, the latter as a result of a 4–13% increase ( P < 0.0006) in ALB and GLB values. Experiment 3 evaluated the effects of storage length (0–26 weeks) and freezing temperatures (−20 °C vs. − 80 °C) on plasma samples ( n = 16–20 blood samples collected in tubes containing sodium fluoride and potassium oxalate). All nitrogenous metabolites were affected by length of storage ( P < 0.0001). Plasma AMN, URN, TP, and NAG were affected (0.0001 < P < 0.10) by storage temperature, and AMN, TP, GLB, and NAG measurements exhibited a temperature × day interaction ( P < 0.05). In general, TP and NAG values declined with storage length, whereas URN, GLB, and AMN values increased. Plasma AMN increased 74% by Week 1 and 160% by Week 9, and samples stored at −20 °C were 14% higher than samples stored at −80 °C ( P < 0.0001). Experiment 4 assessed the effects of storage of whole blood samples ( n = 15 blood samples collected for serum) at 4 °C for 0–7 days. Serum URN and GLB decreased ( P < 0.0001), and TP and AMN increased (0.0001 < P < 0.02) with increasing refrigeration time. Standardized analytical procedures must be followed to obtain reliable nitrogenous metabolite measurements.

Effects of mesenteric vein L-alanine infusion on liver metabolism in beef heifers fed on diets differing in forage: concentrate ratio

Effects of 24 h mesenteric vein infusion of L-alanine (75 mmol/h) and diet forage:concentrate ratio on net nutrient metabolism by portal-drained viscera (PDV) and liver were measured in four Hereford-Angus heifers. Heifers were fed on diets containing approximately 750 g lucerne (Medicago sativa) or 750 g concentrate/kg every 2 h at similar metabolizable energy intakes in a balanced single reversal design with 6 weeks for diet adaptation. Measurements of blood flow and net metabolism of nutrients were obtained at 30 min intervals starting immediately before (four measurements) and after (five measurements) beginning, immediately before ending (four measurements) and 1.5 h after ending (three measurements) alanine infusion. Only values obtained immediately before beginning and ending alanine infusion were compared statistically. Net total splanchnic (PDV plus liver) release of glucose was greater when heifers were fed on the 750 g concentrate/kg v. 750 g lucerne/kg diet due to greater net PDV absorption. Net PDV absorption of ammonia-nitrogen, beta-hydroxybutyrate (BOHB) and lactate, and net liver and total splanchnic release of urea-N (UN) were greater when heifers were fed on the 750 g lucerne/kg v. 750 g concentrate/kg diet. Infusion of alanine increased net liver removal of alanine and alpha-amino-N, net liver release of UN and net total splanchnic release of alanine, UN and lactate. Infusion of alanine decreased net liver release of BOHB and removal of lactate. Mesenteric vein infusion of alanine altered the net availability of precursors for liver glucose synthesis, but did not affect net glucose release by liver in these beef heifers.

Level of nutrition and splanchnic metabolite flux in young lambs.

Splanchnic metabolite flux was measured in young lambs given access to a high-concentrate diet either ad libitum (ADLIB) or at a maintenance level (MAINT) for 21 d. Net fluxes of urea N (UN), ammonia N (NH3 N), alpha-amino N (AAN), amino acids, glucose (G), and lactate (L) across the liver and portal-drained viscera (PDV) were measured in 11 crossbred ram lambs (35 kg) surgically fitted with indwelling catheters in the portal, hepatic, and mesenteric veins and mesenteric artery. During the 21-d period, daily N and ME intakes were 24.6 and 10.7 g N/d and 3.02 and 1.28 Mcal/d, respectively, for ADLIB and MAINT lambs. Intakes, thus, were 42% lower for MAINT than for ADLIB lambs. Net portal fluxes of UN, NH3 N, AAN, and L in MAINT lambs were 46%, 84%, 50%, and 74%, respectively, of that in ADLIB lambs. Expressed as a percentage of N intake, the proportion of AAN absorbed by the PDV was higher in MAINT lambs (P less than .05) than in ADLIB lambs. There was no net portal glucose absorption in either group of lambs; however, net hepatic glucose production in MAINT lambs was 48% of that in ADLIB lambs. There was net utilization of glutamine by the PDV; net glutamine flux in MAINT lambs was 49% of that in ADLIB lambs. The liver utilized AAN and NH3 N and produced UN. Splanchnic tissues modulate metabolite flux following changes in feed intake in young ruminants.

1651 THE EFFECT OF DIALYSATE VOLUME ON PERITONEAL CLERANCES AND ON THE DEVELOPMENT OF HERNIAS IN CHILDREN TREATED WITH CAPD/CCPD

The relation between inflow volume (IV), peritoneal clearance (PC) and development of hernias is not well established in pediatric pts. We therefore performed 73 PC studies in 40 CAPD/CCPD pts. aged 12.4 ± 5.4 (SD) yrs. After a 2 hr dwell with different IV a peritoneal fluid sample was obtained and clearances (C) of creatinine (Cr), urea-N (U-N), potassium (K), uric acid (UA) and phosphorus (P) were obtained. According to the IV, the pts. were placed in 3 different groups (A=20-34.9, 8=35-44.9, C=45-66 cc/kg). In groups A, B, C the mean PCCr corrected for 70 kg BW were 9.4 ± 3.6, 11.1 ± 3.8, 14.4 ± 4.6 ml/rain respectively (A vs B p=NS, B vs C p<0.05, A vs C p<0.005). PCU-N were 1.9 ± 2.8 (A), 14.8 ± 3.5 (B) and 19.5 ± 3.5 (C) ml/min/70 kg respectively (A vs B p<0.005, B vs C p<0.001, A vs c p<0.001). PCK and P were significantly higher with the increased volumes (K: 11.3 ± 2.8, 13.8 ± 3.2, 18.3 ±2.2 ml/min/70 kg p<0.05, <0.001, <0.001). P: 8.7 ± 2.6, 8.9 ± 3.9, 12.0 ± 3.1 ml/min/70 kg, p=NS, <0.05, <0.05). Only the PCUA failed to increase with increased volumes (8.7 ± 2.5, 9.0 ± 2.4, 11.8 ± 3.7 ral/min/70 kg p=NS). Seventeen of the 40 pts developed 27 inguinal, ventral or umbilical hernias after 16.5 ± 11.7 mos of dialysis with an IV ranging between 25.6 and 48.4cc/kg (mean 37.3 ± 5.9). These data indicate that maximal dialysate volumes provide greater C. The IV does not per se effect hernia development. Pts should be carefully evaluated for hernias at the time of initiation of PD.

934 HUMAN MILK: COMPARISON OF NITROGEN (N) COMPOSITION IN MILK FROM MOTHERS GIVING BIRTH PREMATURELY OR AT TERM

Complete 24-hour expressions of human breast milk were collected serially from 7 mothers giving birth at 26-33 wk gestation (Premature,PT) and 8 mothers at 38-40 wk gestation (Full-term,FT) during the first 29 days postpartum. Individual milk samples (69) were analyzed for total N concentration. The regression lines describing the change in N concentration (y) with time in days (d) were y=368 - 4.36d (r=-0.60,p<0.01), and y=310 - 4.15d (r=-0.80,p<0.01), for PT and FT, respectively. Total N concentration in PT milk was significantly higher (p<0.01) than in FT milk over the time studied. The distribution of total N in non-protein N (NPN) and protein N was determined on 7 PT and 8 FT pooled milk samples, representing specific day intervals within each group. NPN as a percent of total N remained constant over the first 29 days of lactation and was similar in the two groups (FT=18.9±0.7,PT=17.8±0.8, mean ± SEM). The proportions of N derived from free amino acid N (FAAN) and urea N(UN) were constant with time and as a percentage of NPN were similar in the FT(7.9±0.4 FAAN;26.8±1.7UN) and PT (8.4±0.7FAAN;25.8±2.0 UN) groups. It is concluded that the higher N concentration of PT milk is due to proportional increments in both the protein and NPN fractions.