bluuebunny/crossref_metadata_2025 huggingface dataset:
Runoff and Interrill Erosion in Sodic Soils Treated with Dry PAM and Phosphogypsum
Authors: Tang Z. , Lei T. , Yu J. , Shainberg I. , Mamedov A. I. , Ben-Hur M. , Levy G. J.
Published: February 2006

Seal formation at the soil surface during rainstorms reduces rain infiltration and leads to runoff and erosion. An increase in soil sodicity increases soil susceptibility to crusting, runoff, and erosion. Surface application of dissolved polyacrylamide (PAM) mixed with gypsum was found to be very effective in decreasing seal formation, runoff, and erosion. The objective of this study was to investigate the effects of surface application of dry granular PAM (20 kg ha−1) mixed with phosphogypsum (PG) (2 and 4 Mg ha−1) and that of PG alone on the infiltration rate (IR), runoff, and wash erosion from four smectitic soil types (ranging in clay content between 10 and 62% and sodicity level between exchangeable sodium percentage [ESP] 2 and 20) exposed to simulated distilled water rainstorms. Increasing ESP from 5 to 20 in the loamy sand decreased final IR from 14 to 2 mm h−1 and increased runoff and wash erosion in the control; similar trends but of different magnitude were noted in the other soil types. Spreading PAM mixed with PG or PG alone was effective in maintaining final IR > 12 mm h−1, low runoff, and wash erosion levels compared with their control. Use of PAM mixed with PG resulted in higher final IR and lower runoff levels than PG alone in all four soils studied. Conversely, with respect to soil erosion, PAM mixed with PG was more effective than PG alone in reducing wash erosion from the loamy sand and clay and had comparable effects on soil loss in the loam. It was concluded that for rain‐fed agriculture, spreading of dry granular PAM mixed with PG was more effective than PG alone in reducing runoff and erosion in soils varying in texture and sodic conditions.
Development of Pedotransfer Functions in Soil Hydrology
Authors: Shukla M. K. , Sammis T. W.
Published: February 2006

Developments in Soil Science Vol. 30. Edited by Ya. Pachepsky and W.J. Rawls. Elsevier, Amsterdam, Boston, 2004. 512 p. $196. ISBN 0‐444‐51705‐7. Hardcover. ISSN 0166‐2481 (series).
New Discoveries in Agrochemicals
Authors: Ma Qingli
Published: February 2006

Edited by J. M. Clark and H. Ohkawa, Oxford University Press, 198 Madison Ave., New York, NY 10016‐4308. 2004. 425p. $145.00. ISBN 0‐8412‐3903‐7.
Soil Chemistry with Applied Mathematics
Authors: Seaman John C.
Published: February 2006

Cristian P. Schulthess, University of Connecticut, Storrs, CT 06269–4067. Trafford Publishing (www.trafford.com), 6E‐2333 Government St., Victoria, B.C., Canada. 2005. 292 pages, $60.00 plus S&H, ISBN 1–4120–3585–6.
Chemical Processes in Soils
Authors: Delgado Jorge A.
Published: February 2006

Edited by M.A. Tabatabai and D.L. Sparks. Soil Science Society of America, Inc., 677 South Segoe Road, Madison, WI 53711, USA. 2005. 723 pages. $90 (members $72). ISBN 0–89118–843–6.
Land Use Effects on the Distribution of Labile Organic Carbon Fractions through Soil Profiles
Authors: Jinbo Zhang , Changchun Song , Wenyan Yang
Published: February 2006

Labile fractions of organic matter can respond rapidly to changes in C supply and are considered to be important indicators of soil quality. However, much less is known on the impact of different land use systems and depth on labile organic matter fractions. The objective of this study was to estimate land use effects on a distribution of labile fraction organic C through soil profiles in the Sanjiang Plain of northeast China. Four land‐use types were selected: Deyeuxia angustifolia wetland, upland forest, two farmlands (cultivated 9 and 15 yr, respectively) of soils previously under Deyeuxia angustifolia wetland, and abandoned cultivated soil. Soil total organic C (TOC), dissolved organic C, microbial organic C, and hot water‐extractable C were measured. The results showed that the intact Deyeuxia angustifolia wetland soil had significantly higher labile fraction organic C contents in the topsoil when compared with upland forest, abandoned cultivated, and cultivated soils. However, there were no significant subsoil differences at all sites. The effects of land use on labile fraction organic C occurred mainly in the topsoil (0–20 cm). The labile fraction organic C contents decreased significantly with increasing soil depth in the intact Deyeuxia angustifolia wetland. However, the upland forest, abandoned cultivated, and cultivated soils showed a considerably smaller decrease in labile fraction organic C contents with increasing soil depth. The proportion of dissolved organic C, hot water‐extractable C, and microbial biomass C to TOC increased to a maximum at a depth of about 20 to 30 cm, and then decreased with increasing soil depth in the Deyeuxia angustifolia wetland but not the other land use types.
Beerkan Estimation of Soil Transfer Parameters through Infiltration Experiments—BEST
Authors: Lassabatère L. , Angulo-Jaramillo R. , Soria Ugalde J. M. , Cuenca R. , Braud I. , Haverkamp R.
Published: February 2006

Studying soil hydrological processes requires the determination of soil hydraulic parameters whose assessment using traditional methods is expensive and time‐consuming. A specific method, Beerkan estimation of soil transfer parameters referred to as BEST was developed to facilitate the determination of both the water retention curve, θ(h), and the hydraulic conductivity curve, K(θ), defined by their shape and scale parameters. BEST estimates shape parameters from particle‐size distribution analysis and scale parameters from infiltration experiments at null pressure head. Saturated water content is measured directly at the end of infiltration. Hydraulic conductivity and water pressure scale parameters are calculated from the steady‐state infiltration rate and prior estimation of sorptivity (S) This is provided by fitting transient infiltration data on the classical two‐term equations with values from zero to a maximum corresponding to null hydraulic conductivity and using a data subset for which the two‐term infiltration equations are verified as valid. BEST was compared with other fitting methods to estimate sorptivity and hydraulic conductivity from infiltration modeling data on the basis of the same infiltration equations for three contrasting soils: agricultural soil, sandy soil, and a coarser fluvioglacial deposit. The other methods failed sometimes to model accurately experimental data and to provide values in agreement with physical principles of water infiltration (negative values for hydraulic conductivity, too high steady‐state infiltration rate). None of these anomalies was encountered when modeling cumulative infiltration with BEST. BEST appears to be a promising, easy, robust, and inexpensive way of characterizing the hydraulic behavior of soil.
Emissions of Nitrous Oxide and Carbon Dioxide
Authors: Drury C. F. , Reynolds W. D. , Tan C. S. , Welacky T. W. , Calder W. , McLaughlin N. B.
Published: February 2006

Innovative management practices are required to increase the efficiency of N fertilizer usage and to reduce nitrous oxide (N2O) and carbon dioxide (CO2) emissions from agricultural soils. The objectives of this study were to evaluate the feasibility of using conservation tillage and N fertilizer placement depth to reduce N2O and CO2 emissions associated with corn (Zea mays L.) production on clay loam soils in Eastern Canada. A 3‐yr field study was established on a wheat (Triticum aestivum L.)‐corn–soybean [Glycine max (L.) Merr.] rotation with each phase of the rotation present every year. Investigations were focused on the corn phase of the rotation. The tillage treatments following winter wheat included fall moldboard plow tillage (15 cm depth), fall zone‐tillage (21 cm width, 15 cm depth), and no‐tillage. The N placement treatments were “shallow” placement of sidedress N (2‐cm depth) and “deep” placement of sidedress N (10‐cm depth). Nitrous oxide emissions were measured 53 times and CO2 emissions were measured 43 times over three growing seasons using field‐based sampling chambers. There was a significant tillage and N placement interaction on N2O emissions. Averaged over all three tillage systems and site‐years, N2O emissions from shallow N placement (2.83 kg N ha−1 yr−1) were 26% lower than deep N placement (3.83 kg N ha−1 yr−1). The N2O emissions were similar among the tillage treatments when N was placed in the soil at a shallow depth. However, when N was placed deeper in the soil (10 cm), the 3‐yr average N2O emissions from zone‐tillage (2.98 kg N ha−1 yr−1) were 20% lower than from no‐tillage (3.71 kg N ha−1 yr−1) and 38% lower than those from moldboard plow tillage (4.81 kg N ha−1 yr−1). Tillage type and N placement depth did not affect CO2 emissions (overall average = 5.80 Mg C ha−1 yr−1). Hence, zone‐tillage and shallow N placement depth reduced N2O emissions without affecting CO2 emissions.
Flow‐Through and Batch Methods for Determining Calcium‐Magnesium and Magnesium‐Calcium Selectivity
Authors: DeSutter Tom M. , Pierzynski Gary M. , Baker Luke R.
Published: February 2006

Conducting binary‐exchange experiments is a common way to identify cationic preferences of exchanger phases and the two most common approaches are the flow‐through and batch methods. The objectives of this research were to provide the materials and methods for both flow‐through and batch equilibration techniques and to compare Ca‐Mg and Mg‐Ca selectivity when using these two methods on a montmorillonitic soil. The methods were evaluated by comparing both the Gibbs free energy values (ΔGex) and selectivity diagrams derived from the flow‐through and batch exchange reactions. The ΔGex values for the Ca‐Mg reaction were 634 and 444 J mol−1 as determined by the flow‐through and batch methods, respectively, indicating an exchanger preference for Ca. Exchanger preference for Ca was also evident in the Mg‐Ca reaction with ΔGex values of −882 and −784 J mol−1 for the flow‐through and batch methods, respectively. The flow‐through and batch methods worked very well for determining cation selectivity and results indicate no significant differences existed between the two methods.
Tillage and Crop Rotation Effects on Dryland Soil and Residue Carbon and Nitrogen
Authors: Sainju Upendra M. , Lenssen Andrew , Caesar-Tonthat Thecan , Waddell Jed
Published: February 2006

Sustainable management practices are needed to enhance soil productivity in degraded dryland soils in the northern Great Plains. We examined the effects of two tillage practices [conventional till (CT) and no‐till (NT)], five crop rotations [continuous spring wheat (Triticum aestivum L.) (CW), spring wheat‐fallow (W‐F), spring wheat‐lentil (Lens culinaris Medic.) (W‐L), spring wheat‐spring wheat‐fallow (W‐W‐F), and spring wheat‐pea (Pisum sativum L.)‐fallow (W‐P‐F)], and a Conservation Reserve Program (CRP) on plant biomass returned to the soil, residue C and N, and soil organic C (SOC), soil total N (STN), and particulate organic C and N (POC and PON) at the 0‐ to 20‐cm depth. A field experiment was conducted in a mixture of Scobey clay loam (fine, smectitic, frigid Aridic Argiustolls) and Kevin clay loam (fine‐loamy, mixed, superactive, frigid Aridic Argiustolls) from 1998 to 2003 near Havre, MT. Mean annualized plant biomass returned to the soil from 1998 to 2003 was greater in W‐F (2.02 Mg ha−1) than in W‐L and W‐W‐F, regardless of tillage. In 2004, residue cover was greater in CW (60%) than in other rotations, except in W‐W‐F. Residue amount and C and N contents were greater in NT with CW (2.47 Mg ha−1 and 963 and 22 kg ha−1, respectively) than in NT with W‐L and CT with other crop rotations. The POC at 0 to 5 cm was greater in W‐W‐F and W‐P‐F (2.1–2.2 Mg ha−1) than in W‐L. Similarly, STN at 5 to 20 cm was greater in CT with W‐L (2.21 Mg ha−1) than in other treatments, except in NT with W‐W‐F. Reduced tillage and increased cropping intensity, such as NT with CW and W‐L, conserved C and N in dryland soils and crop residue better than the traditional practice, CT with W‐F, and their contents were similar to or better than in CRP planting.
Soil Compaction Induced by Small Tractor Traffic in Northeast China
Authors: Zhang X. Y. , Cruse R. M. , Sui Y. Y. , Jhao Z.
Published: February 2006

With the introduction of the small four‐wheel tractors (ST), agricultural mechanization has developed rapidly in China. In this study, we investigated the impact of these relatively small tractors on soil compaction of a silty clay loam (fine‐silty, mixed, superactive, mesic Typic Argiboroll) in northeast China using soil penetration resistance (PR) and bulk density as soil compaction indicators. The relationship between soil water content and PR, the comparison of soil compaction induced by ST and the medium power tractor (MT), the effect of tractor mass on compaction, the effect of number of tractor passes and tillage on PR, and the effect of compaction on crop yield were studied. Compared with MT‐powered tillage, the ST‐powered tillage system created a more compacted plow layer due to increased passes required with this system. Small four‐wheeled tractors had a statistically significant higher PR than MT in the topsoil and subsoil. The PR had a significant negative correlation (r = − 0.640, P < 0.01) with soil water content at time of PR measurement. After trafficking in a wheat (Triticum aestivum L.) field, the highest PR values were found in the 5‐ to 14‐cm depth interval. Crop yield decreased with increasing numbers of tractor passes. There were different yield‐loss responses to compaction for spring wheat and corn (Zea mays L.). With the development of mechanical tillage in China, the problem of soil compaction may be significantly increased, causing potential yield reductions.
Stress Induced Water Content Variations in Mango Stem by Time Domain Reflectometry
Authors: Nadler A. , Raveh Eran , Yermiyahu Uri , Green S.
Published: February 2006

Close, direct, and accurate monitoring of the plant water status may serve as a practical (irrigation scheduling) and a research (climate–environmental induced physiologic changes) tool. Methods for high‐frequency capacitance measurement (e.g., time domain reflectometry [TDR]) possess the potential for high resolution dielectric measurements with minimal dependence on properties of the measured matrix. The objective of this study is to test the accuracy, response time, and sensitivity of the TDR methodology in measuring changes in water status in a mango (Mangifera indica L., Cultivar ‘Kent’) tree stem exposed to several perturbations concerning water, salinity, fruit load, and radiation. Under several induced stress conditions, stem and root zone water content (θ) and electrical conductivity (σ) were simultaneously measured. Our study is distinct in its detailed and frequent measurements of stem water content (θstem) using short (29–70 mm) TDR probes in trees growing in a detached medium. We have found that θstem response to root zone applied salinity and water stress were negative and positive, respectively. Stem electrical conductivity (σstem) was primarily dependent on θstem and only negligibly on stem cells salinity. The θstem response time to water application was ∼4 h. Two practical outcomes of our study were: (1) Because the salt content of the tree cells only slightly affected σstem, stem resistivity measurements could be used to represent dielectric changes, and (2) quite short probes could be used to include young trees of slim tree branches.
Phosphorus and Potassium Distribution in Soil Following Long‐Term Deep‐Band Fertilization in Different Tillage Systems
Authors: Mallarino Antonio P. , Borges Rogerio
Published: February 2006

Tillage and fertilizer placement affect soil‐test P (STP) and K (STK) distribution in topsoil but little is known about stratification after deep banding. This study investigated lateral and vertical STP and STK stratification after deep‐banding fertilizers for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] managed with no‐till or chisel‐disk tillage. Soil samples were collected from selected plots of 10 Iowa trials (five for P and five for K) having 4‐yr treatment histories. Treatments sampled (three replications of each) were no‐till and chisel‐disk tillage with or without deep‐band fertilization. Either 28 kg P ha−1yr−1 or 66 kg K ha−1yr−1 was banded 13 to 18 cm deep and spaced 76 cm. Crop rows were planted on top of the fertilizer bands. Soil samples were collected at 5‐cm increments to a 30‐cm depth from band/row (BR) and interband/interrow (IBR) positions. Vertical nutrient stratification was observed for all treatments but was more evident for BR with no‐till. Lateral stratification was not observed in nonfertilized plots. At a 5‐cm depth, both nutrients were higher for BR than for IBR only with no‐till management. At a 5‐ to 15‐cm depth both nutrients were higher for BR than for IBR with both tillage systems, but at deeper depths lateral stratification was less evident across nutrients and sites. Vertical and lateral stratification were more pronounced for STP than for STK. Higher crop K uptake and recycling than for P could explain this difference. The results indicate that vertical and lateral stratification due to deep‐band fertilization is of concern when planning soil sampling for no‐till and may also be of concern for chisel‐disk tillage.
Cadmium and Zinc in Saline Soil Solutions and their Concentrations in Wheat
Authors: Khoshgoftarmanesh Amir H. , Shariatmadari H. , Karimian N. , Kalbasi M. , van der Zee S. E. A. T. M.
Published: February 2006

Soil salinity and plant genotype may affect bioavailability of Cd and Zn to wheat. The aim of this study was to investigate the relationship between concentrations of Zn and Cd in saline soil solutions and in different wheat genotypes. A greenhouse experiment with four bread wheat genotypes (Triticum aestivumL. cv. Rushan, Kavir, Cross, and Falat), and a durum wheat (Triticum durumL. cv. Durum), at four salinity levels of irrigation water (0, 60, 120, and 180 mMNaCl) in triplicate was conducted. After 45 d of growth, the shoots were harvested, and Zn and Cd concentrations were determined in the shoots. Speciation of Cd and Zn in saturation paste extract was modeled using MINTEQA2. A significant (P< 0.05) correlation was observed between model results and Cd and Zn species measured using Amberlite resin. Cadmium and Zn speciation in MINTEQA2‐calculated soil solution was affected by salinity but not by wheat genotype. The major Cd species present in MINTEQA2‐calculated soil solution were free Cd2+, CdCl+, and CdSO40, that increased with increasing salinity. Free Zn2+was the dominant Zn‐species for all salinities and decreased with increasing salinity. Increasing salinity resulted in significant increases and decreases in shoot Cd and Zn concentrations, respectively, of the Zn‐inefficient genotypes. Cadmium concentrations in shoots of Durum and Kavir genotypes were best predicted by CdCl+concentrations in solution. In contrast, free Zn2+ion concentrations in MINTEQA2 calculated soil solution were best related to shoot Zn concentrations in Zn‐efficient genotypes. Under saline conditions, Zn and Cd speciation effects on bioavailability thus depend on both plant genotype and the metal of interest.
Harvesting Intensity at Clear‐Felling in the Boreal Forest
Authors: Thiffault Evelyne , Paré David , Bélanger Nicolas , Munson Alison , Marquis François
Published: February 2006

The amount of logging residues left on site after clear‐felling has been shown to influence the state of soil nutrient resources, but this effect may depend on soil conditions. In three regions of the boreal zone of Quebec, with contrasting soil characteristics, soil and foliar nutrient status of young (15–20 yr old) stands were compared among sites that were clear‐felled at two harvesting intensities, that is, stem‐only (SOH) and whole‐tree harvesting (WTH). Balsam fir (Abies balsamea) stands were studied in the Forêt Montmorency and Gaspésie regions, while black spruce [Picea mariana (Mill.) B.S.P.] and jack pine (Pinus banksiana Lamb.) were studied in the Haute‐Mauricie region. Whole‐tree harvesting resulted in lower cation exchange capacity (CEC) compared with SOH, but this effect could be linked to decreased levels of organic C only in the Haute‐Mauricie region, where soils had intrinsically low organic matter content. Lower soil and foliar Ca concentrations after WTH were observed in all three regions. Foliar Ca status was most strongly affected by harvesting intensity in Gaspésie, where soils exhibited the lowest concentration of total Ca in the parent material. In Haute‐Mauricie, where the parent material contained a low level of Mg, foliar nutrition for this element was significantly poorer under WTH compared with SOH. Harvesting intensity did not influence the biogeochemical cycles of K and N. Foliar analysis revealed that jack pine exhibits the strongest nutritional difference between WTH and SOH. Results suggested that the tree species regenerating the harvested sites, as well as the total Ca and Mg contents of the parent material are better indicators of a site's susceptibility to nutritional alteration by WTH than soil available nutrient status.
Analysis of Factors Controlling Soil Carbon in the Conterminous United States
Authors: Guo Yinyan , Gong Peng , Amundson Ronald , Yu Qian
Published: February 2006

Maps of soil organic carbon (SOC) and inorganic carbon (SIC) were generated from the State Soil Geographical database (STATSGO) and were overlain with land‐cover, topography (elevation and slope), mean annual precipitation (MAP), and mean annual temperature (MAT) databases to study the effects of environmental driving factors (or “state factors”) in the conterminous USA. In the USA, human disturbance has significantly reduced SOC and SIC in the surface layer. The SOC decreases as elevation increases. Level topography has twice the SOC content of other slope classes. Soil organic C increases as MAP increases up to values of 700–850 mm yr−1 There is no obvious pattern in SIC as MAP increases until MAP exceeds 1000 mm, at which point on SIC drops dramatically. For natural vegetation with MAP < 1000 mm, SOC decreases as MAT increases (within restricted ranges of elevation and topography). The relationship between SOC versus MAT varies with MAP, and SOC is most sensitive to temperature in low and moderate MAP regions and in the upper soil layers. This GIS‐based analysis is a relatively coarse evaluation given the nature of the database, but does provide a first quantitative assessment of soil C to “state factors” for the USA as a whole using commonly available digital databases.
Experimental Limitations of Time Domain Reflectometry Hardware for Dispersive Soils
Authors: Logsdon S. D.
Published: February 2006

Time domain reflectometry (TDR) has been used to determine soil water content. Multiple attachments and long cables may result in unreliable data for dispersive soils, but these attachments are necessary for automated field monitoring at multiple sites and depths. The objective of this study was to experimentally determine the effect of attachments on the TDR waveform for a parallel probe with a balun. The probe with parallel waveguides and balun was successively attached to the front panel of the cable tester (Level 1), to a transient suppressor (Level 2), to the first level multiplexer (Level 3), or to a second level multiplexer (Level 4). Each attachment level significantly reduced frequency bandwidth, and Level 4 frequency bandwidth was about half that of Level 1. The greatest attenuation decrease was between Levels 1 and 2. Attenuations due to TDR hardware make it difficult to obtain useful waveforms for determining soil water content.
A Small‐Scale Matric Potential Sensor Based on Time Domain Reflectometry
Authors: Persson Magnus , Wraith Jon M. , Dahlin Torleif
Published: February 2006

Measurements of soil matric potential (ψ) are needed in many soil science applications. In the present study, a small matric potential sensor having a length of 30 mm and a diameter of 9.6 mm was developed. The sensor consists of two coils made of lacquer‐coated copper wires embedded in gypsum. The dielectric constant of the gypsum (Kgypsum) was measured with time domain reflectometry (TDR). The gypsum probes were tested in a sandy loam soil using a pressure extractor to obtain the relationship between Kgypsum and ψ, allowing inference of the soil ψ in equilibrium with the sensor. It was shown that the gypsum probe could give ψ estimates with a root mean square error (RMSE) of around 50 kPa in the range of −20 to −1500 kPa. Most of the sensitivity of the sensor was in the −50‐ to −1000‐kPa range.
Kinetics of Phosphate Sorption to Polygalacturonate‐coated Goethite
Authors: Mikutta Christian , Lang Friederike , Kaupenjohann Martin
Published: February 2006

Biogenetic polysugars may affect the sorption characteristics of soil mineral particles in the rhizosphere. We hypothesized that polygalacturonate [PGA, (C6H7O6)n−] coatings on goethite reduce the diffusion of phosphate into the pores of the adsorbent. Goethite was preloaded with PGA (0–10 mg C g−1). The samples were characterized by N2 and CO2 adsorption, electrophoretic mobility measurements, and scanning electron microscopy/energy dispersive X‐ray analysis (SEM‐EDX). The phosphate sorption kinetics was studied with batch experiments over 2 wk at pH 5 and an initial phosphate concentration of 250 μM Pore volume and specific surface area of the goethite samples declined after PGA addition. The PGA coatings reduced the ζ‐potential of goethite from 42.3 to −39.6 mV at the highest C loading. With increasing PGA‐C content and decreasing ζ‐potential the amount of phosphate sorbed after 2 wk decreased linearly (P < 0.001). Sorption of phosphate to pure and PGA‐coated goethite showed an initial fast sorption followed by a slow sorption reaction. At the smallest C loading (5.5 mg C g−1) the portion of phosphate retained by the slow reaction was smaller than for the treatment without any PGA, while at higher C loadings the fraction of slowly immobilized phosphate increased. Our results suggest that at low C‐loadings PGA impaired the intraparticle diffusion of phosphate. In contrast, the slow step‐by‐step desorption of PGA (<52% within 2 wk) or the diffusion of phosphate through PGA coatings or both are rate limiting for the slow phosphate reaction at C loadings > 5.5 mg C g−1
Cardiovascular effects of desflurane in mechanically ventilated calves
Authors: Keegan Robert D. , Greene Stephen A. , Valdez Reginald A. , Knowles Donald K.
Published: February 2006

Objective—To determine cardiovascular effects of desflurane in mechanically ventilated calves.

Animals—8 healthy male calves.

Procedure—Calves were anesthetized by face mask administration of desflurane to permit instrumentation. Administration of desflurane was temporarily discontinued until mean arterial blood pressure increased to ≥ 100 mm Hg, at which time baseline cardiovascular values, pulmonary arterial temperature, end-tidal CO2 tension, and end-tidal desflurane concentration were recorded. Cardiac index and systemic and pulmonary vascular resistances were calculated. Arterial blood gas variables were measured and calculated. Mean end-tidal concentration of desflurane at this time was 3.4%. After collection of baseline values, administration of 10% end-tidal concentration of desflurane was resumed and calves were connected to a mechanical ventilator. Cardiovascular data were collected at 5, 10, 15, 30, and 45 minutes, whereas arterial blood gas data were collected at 15 and 45 minutes after collection of baseline data.

Results—Mean ± SD duration from beginning desflurane administration to intubation of the trachea was 151 ± 32.8 seconds. Relative to baseline, desflurane anesthesia was associated with a maximal decrease in arterial blood pressure of 35% and a decrease in systemic vascular resistance of 34%. Pulmonary arterial blood temperature was decreased from 15 through 45 minutes, compared with baseline values. There were no significant changes in other measured variables. All calves recovered from anesthesia without complications.

Conclusions and Clinical Relevance—Administration of desflurane for induction and maintenance of general anesthesia in calves was smooth, safe, and effective. Cardiopulmonary variables remained in reference ranges throughout the study period.
Median effective dose of isoflurane, sevoflurane, and desflurane in green iguanas
Authors: Barter Linda S. , Hawkins Michelle G. , Brosnan Robert J. , Antognini Joseph F. , Pypendop Bruno H.
Published: February 2006

Objective—To determine the median effective dose (ED50; equivalent to the minimum alveolar concentration [MAC]) of isoflurane, sevoflurane, and desflurane for anesthesia in iguanas.

Animals—6 healthy adult green iguanas.

Procedure—In unmedicated iguanas, anesthesia was induced and maintained with each of the 3 volatile drugs administered on separate days according to a Latin square design. Iguanas were endotracheally intubated, mechanically ventilated, and instrumented for cardiovascular and respiratory measurements. During each period of anesthesia, MAC was determined in triplicate. The mean value of 2 consecutive expired anesthetic concentrations, 1 that just permitted and 1 that just prevented gross purposeful movement in response to supramaximal electrical stimulus, and that were not different by more than 15%, was deemed the MAC.

Results—Mean ± SD values for the third MAC determination for isoflurane, sevoflurane, and desflurane were 1.8 ± 0.3%, 3.1 ± 1.0%, and 8.9 ± 2.1% of atmospheric pressure, respectively. The MAC for all inhaled agents was, on average, 22% greater for the first measurement than for the third measurement.

Conclusions and Clinical Relevance—Over time, MACs decreased for all 3 agents. Final MAC measurements were similar to values reported for other species. The decrease in MACs over time may be at least partly explained by limitations of anesthetic uptake and distribution imposed by the reptilian cardiorespiratory system. Hence, for a constant end-tidal anesthetic concentration in an iguana, the plane of anesthesia may deepen over time, which could contribute to increased morbidity during prolonged procedures.
Effects of phenylbutazone alone or in combination with flunixin meglumine on blood protein concentrations in horses
Authors: Reed Shannon K. , Messer Nathaniel T. , Tessman Ronald K. , Keegan Kevin G.
Published: February 2006

Objective—To assess effects of treatment with phenylbutazone (PBZ) or a combination of PBZ and flunixin meglumine in horses.

Animals—24 adult horses.

Procedure—13 horses received nonsteroidal antiinflammatory drugs (NSAIDs) in a crossover design. Eleven control horses were exposed to similar environmental conditions. Treated horses received PBZ (2.2 mg/kg, PO, q 12 h, for 5 days) and a combination of PBZ and flunixin meglumine (PBZ, 2.2 mg/kg, PO, q 12 h, for 5 days; flunixin meglumine, 1.1 mg/kg, IV, q 12 h, for 5 days). Serum samples were obtained on day 0 (first day of treatment) and day 5, and total protein, albumin, and globulin were measured.

Results—1 horse was euthanatized with severe hypoproteinemia, hypoalbuminemia, and colitis during the combination treatment. Comparisons revealed no significant difference between control horses and horses treated with PBZ alone. There was a significant difference between control and treated horses when administered a combination of PBZ and flunixin meglumine. Correction for horses with values >2 SDs from the mean revealed a significant difference between control horses and horses administered the combination treatment, between control horses and horses administered PBZ alone, and between horses receiving the combination treatment and PBZ alone. Gastroscopy of 4 horses revealed substantial gastric ulcers when receiving the combination NSAID treatment.

Conclusions and Clinical Relevance—Analysis of results of the study indicates the need for caution when administering a combination NSAID treatment to horses because the detrimental effects may outweigh any potential benefits.
Gentamicin concentrations in synovial fluid and joint tissues during intravenous administration or continuous intra-articular infusion of the tarsocrural joint of clinically normal horses
Authors: Lescun Timothy B. , Ward Michael P. , Adams Stephen B.
Published: February 2006

Objective—To compare gentamicin concentrations achieved in synovial fluid and joint tissues during IV administration and continuous intra-articular (IA) infusion of the tarsocrural joint in horses.

Animals—18 horses with clinically normal tarsocrural joints.

Procedure—Horses were assigned to 3 groups (6 horses/group) and administered gentamicin (6.6 mg/kg, IV, q 24 h for 4 days; group 1), a continuous IA infusion of gentamicin into the tarsocrural joint (50 mg/h for 73 hours; group 2), or both treatments (group 3). Serum, synovial fluid, and joint tissue samples were collected for measurement of gentamicin at various time points during and 73 hours after initiation of treatment. Gentamicin concentrations were compared by use of a Kruskal-Wallis ANOVA.

Results—At 73 hours, mean ± SE gentamicin concentrations in synovial fluid, synovial membrane, joint capsule, subchondral bone, and collateral ligament of group 1 horses were 11.5 ± 1.5 μg/mL, 21.1 ± 3.0 μg/g, 17.1 ± 1.4 μg/g, 9.8 ± 2.0 μg/g, and 5.9 ± 0.7 μg/g, respectively. Corresponding concentrations in group 2 horses were 458.7 ± 130.3 μg/mL, 496.8 ± 126.5 μg/g, 128.5 ± 74.2 μg/g, 99.4 ± 47.3 μg/g, and 13.5 ± 7.6 μg/g, respectively. Gentamicin concentrations in synovial fluid, synovial membrane, and joint capsule of group 1 horses were significantly lower than concentrations in those samples for horses in groups 2 and 3.

Conclusions and Clinical Relevance—Continuous IA infusion of gentamicin achieves higher drug concentrations in joint tissues of normal tarsocrural joints of horses, compared with concentrations after IV administration.
Serum and synovial fluid concentrations of keratan sulfate and hyaluronan in dogs with induced stifle joint osteoarthritis following cranial cruciate ligament transection
Authors: Budsberg Steven C. , Lenz Mary Ellen , Thonar Eugene J-M. A.
Published: February 2006

Objective—To examine longitudinal changes in serum and synovial fluid concentrations of keratan sulfate (KS) and hyaluronan (HA) after cranial cruciate ligament (CCL) transection in dogs.

Animals—12 clinically normal adult mixed-breed dogs.

Procedure—Following CCL transection in the right stifle joint, KS and HA concentrations were determined in serum and neat (undiluted) synovial fluid prior to and 1, 2, 3, and 12 months after surgery. Postsurgical dilution of synovial fluid was corrected by use of urea as a passive marker.

Results—Synovial fluid KS and HA concentrations decreased at 1, 2, and 3 months after surgery in operated stifle joints, compared with baseline values. Synovial fluid KS concentration decreased in unoperated stifle joints at 1 month. A decrease in synovial fluid KS concentration was found in operated stifle joints, compared with unoperated stifle joints, at 2 and 3 months, and a decrease in synovial fluid HA concentrations was also found in operated stifle joints, compared with unoperated stifle joints, at 1, 2, and 3 months. Serum KS concentrations increased from baseline values at 3 months after surgery. Hyaluronan concentrations in operated stifle joints were lower than baseline values at 1, 2, and 3 months. Urea-adjusted synovial fluid concentrations revealed that dilution did not account for the decline in biomarker concentrations.

Conclusions and Clinical Relevance—The initial decrease and subsequent increase in synovial fluid concentrations of HA and KS may be caused by an acute inflammatory response to surgical intervention that negatively affects cartilage metabolism or an increase in production of immature proteoglycans.
Characterization of experimentally induced post-traumatic osteoarthritis in the medial femorotibial joint of horses
Authors: Bolam Courtney J. , Hurtig Mark B. , Cruz Antonio , McEwen Beverly J. E.
Published: February 2006

Objective—To study osteoarthritis in the equine medial femorotibial (MFT) joint after a single traumatic injury.

Animals—10 mature horses.

Procedure—In vitro explant cultures were used to determine injury threshold for stifle joint cartilage. Contusive impacts were applied to the medial femoral condyle (MFC), and horses were followed for 84 (n = 5) and 180 days (5). Synovial fluid samples were collected every 14 days for determination of sulphated glycosaminoglycan (sGAG) concentrations. Radiographic and lameness evaluations were performed. Gross and histologic descriptions, and immunohistochemistry, cartilage sGAG content determination, and cartilage aggregate modulus determination were performed at the MFC impact site (MFCi), MFC nonimpact site (MFCn), and medial tibial plateau (MTP).

Results—Synovial fluid sGAG concentration decreased significantly on days 14, 28, 42, and 56 in all horses. Macroscopic and microscopic articular lesions developed within all MFT joints. No radiographic abnormalities were observed. Mild lameness was evident in several horses. No significant differences were found between short-term and longterm cohorts of horses with respect to histologic scores and TUNEL results. On immunohistochemistry, MFCi was positive for COL2–¾Cshort. International Cartilage Repair Society scores differed significantly between short-term and long-term cohorts of horses. In all horses, sGAG concentrations were significantly decreased at the MFCi, compared with the MFCn.

Conclusions and Clinical Relevance—Use of contusive impacts on the MFC of horses results in cartilage lesions that are similar to those described clinically, supporting trauma as a contributing factor in the natural pathogenesis of osteoarthritis.
Evaluation of the pharmacokinetics and bioavailability of intravenously and orally administered amiodarone in horses
Authors: De Clercq Dominique , Baert Kris , Croubels Siska , van Loon Gunther , Maes An , Tavernier Rene , Deprez Piet , De Backer Patrick
Published: February 2006

Objective—To determine the clinical effects and pharmacokinetics of amiodarone after single doses of 5 mg/kg administered orally or intravenously.

Animals—6 healthy adult horses.

Procedure—In a cross over study, clinical signs and electrocardiographic variables were monitored and plasma and urine samples were collected. A liquid chromatography–mass spectrometry method was used to determine the percentage of protein binding and to measure plasma and urine concentrations of amiodarone and the active metabolite desethylamiodarone.

Results—No adverse clinical signs were observed. After IV administration, median terminal elimination half-lives of amiodarone and desethylamiodarone were 51.1 and 75.3 hours, respectively. Clearance was 0.35 L/kg•h, and the apparent volume of distribution for amiodarone was 31.1 L/kg. The peak plasma desethylamiodarone concentration of 0.08 μg/mL was attained 2.7 hours after IV administration. Neither parent drug nor metabolite was detected in urine, and protein binding of amiodarone was 96%. After oral administration of amiodarone, absorption of amiodarone was slow and variable; bioavailability ranged from 6.0% to 33.7%. The peak plasma amiodarone concentration of 0.14 μg/mL was attained 7.0 hours after oral administration and the peak plasma desethylamiodarone concentration of 0.03 μg/mL was attained 8.0 hours after administration. Median elimination half-lives of amiodarone and desethylamiodarone were 24.1 and 58.6 hours, respectively.

Conclusion and Clinical Relevance—Results indicate that the pharmacokinetic distribution of amiodarone is multicompartmental. This information is useful for determining treatment regimens for horses with arrythmias. Amiodarone has low bioavailability after oral administration, does not undergo renal excretion, and is highly protein-bound in horses.
Fractionation of calcium and magnesium in equine serum
Authors: Lopez Ignacio , Estepa Jose C. , Mendoza Francisco J. , Mayer-Valor Rafael , Aguilera-Tejero Escolastico
Published: February 2006

Objective—To establish reference values for protein-bound, ionized, and weak-acid complexed fractions of calcium and magnesium in equine serum and determine stability of ionized calcium (iCa) and ionized magnesium (iMg) in serum samples kept under various storage conditions.

Animals—28 clinically normal horses.

Procedure—Total calcium (tCa) and magnesium (tMg) in equine serum were fractionated by use of a micropartition system that allows separation of protein-bound calcium (pCa) and magnesium (pMg) and ultrafiltrable calcium (μCa) and magnesium (μMg) fractions. Serum concentrations of iCa and iMg were measured in the ultrafiltrate by use of selective electrodes. Serum concentration of complexed calcium (cCa) or magnesium (cMg) was calculated by subtracting iCa or iMg from μCa or μMg, respectively.

Results—Mean ±SE serum tCa concentration was 3.26 ± 0.06 mmol/L. Calcium fractions were as follows: pCa, 1.55 ± 0.03 mmol/L (47.4 ± 0.9%); iCa, 1.58 ± 0.03 mmol/L (48.5 ± 0.7%); and cCa, 0.13 ± 0.02 mmol/L (4.1 ± 0.9%). Serum tMg concentration was 0.99 ± 0.04 mmol/L. Magnesium fractions were as follows: pMg, 0.33 ± 0.04 mmol/L (33.3 ± 4.2%); iMg, 0.57 ± 0.02 mmol/L (57.6 ± 1.7%); and cMg, 0.09 ± 0.02 mmol/L (9.1 ± 1.9%). Refrigeration (4°C) did not affect iCa values, whereas iMg declined by 8% after 120 hours. Neither iCa nor iMg was affected by freezing (−20°C).

Conclusions and Clinical Relevance—In equine serum, iMg is less stable than iCa; thus, when serum samples are not going to be analyzed promptly, freezing may be preferable to refrigeration for storage.
Use of helical computed tomography for measurement of thyroid glands in clinically normal cats
Authors: Drost Wm Tod , Mattoon John S. , Weisbrode Steven E.
Published: February 2006

Objective—To determine the dimensions and volume of thyroid tissue in clinically normal cats by use of computed tomography.

Animals—8 cats.

Procedure—Helical computed tomography images (2-mm collimation) were acquired from the cranial aspect of the second cervical vertebra through the caudal aspect of the fourth cervical vertebra. Data were acquired before contrast medium administration (n = 7 cats) and immediately after contrast medium enhancement (1 cat). Length, width, and height measurements of each thyroid lobe were made by use of transverse, dorsal, and sagittal plane images. Thyroid lobe volume was estimated by use of 3 methods.

Results—All thyroid lobes were histologically normal. Mean dimensions for a thyroid lobe were 16.5 × 2.00 × 4.31 mm (length × width × height) using only data from transverse images. Mean thyroid lobar volume was 113.75 mm3 using the sum of areas method. Mean total volume of thyroid tissue was 215.25 mm3 using the sum of areas method.

Conclusions and Clinical Relevance—Results may be useful for computed tomography evaluation of abnormal thyroid glands in cats, which warrants investigation.
Evaluation of gastrointestinal permeability and mucosal absorptive capacity in dogs with chronic enteropathy
Authors: Allenspach Karin , Steiner Joerg M. , Shah Bhavin N. , Berghoff Nora , Ruaux Craig , Williams David A. , Blum Juerg W. , Gaschen Frederic
Published: February 2006

Objective—To assess intestinal mucosal function by measuring permeability and absorptive capacity in dogs with chronic enteropathy (CE) before and after treatment and to determine whether those variables were correlated with clinical disease activity or histologic scoring of intestinal biopsy specimens.

Animals—29 dogs with CE.

Procedure—Dogs were designated as having dietresponsive CE or CE requiring glucorticoid treatment. Severity of clinical signs was assessed by calculating the canine inflammatory bowel disease activity index (CIBDAI). Histologic severity of intestinal infiltration was assessed before and after 4 weeks of treatment in the diet-responsive group and before and after 10 weeks of treatment in the glucocorticoid group. Gastrointestinal permeability and mucosal absorptive capacity were assessed by use of intragastric administration of a solution containing lactulose, rhamnose, xylose, 3-O-methylglucose, and sucrose. Urine was collected 6 hours after administration of the sugar solution to determine urinary lactulose-to-rhamnose (L:R), xylose-to-methylglucose (X:M), and sucrose-to-methylglucose (S:M) ratios.

Results—Median CIBDAI scores decreased significantly in both groups of dogs after treatment. However, the median histologic grade of intestinal biopsy specimens did not change with treatment in either group. There were no significant differences in L:R, X:M, or S:M ratios after treatment in either group and no significant correlations between L:R, X:M, or S:M ratios and CIBDAI or histologic scores.

Conclusions and Clinical Relevance—Results of tests for intestinal permeability and mucosal absorptive capacity were not useful indicators of clinical disease activity as assessed by the CIBDAI or the sever ity of infiltration as indicated by histologic evaluation.
Immunologic responses against hydrolyzed soy protein in dogs with experimentally induced soy hypersensitivity
Authors: Puigdemont Anna , Brazís Pilar , Serra Montserrat , Fondati Alessandra
Published: February 2006

Objective—To assess whether dogs with experimentally induced type I hypersensitivity against soy protein would respond to soy hydrolysate and develop cutaneous or gastrointestinal tract reactions after intradermal and oral challenge exposure.

Animals—12 naïve Beagle pups (9 sensitized and 3 control dogs).

Procedure—9 dogs were sensitized against soy protein by administration of allergens during a 90-day period. After the sensitization period, serum concentrations of soy-specific IgE were determined and an intradermal test was performed to confirm the dogs were sensitized against soy protein. An intradermal challenge test and an oral challenge test with native and hydrolyzed soy protein were conducted on 6 sensitized and 2 control dogs.

Results—High serum concentrations of soy-specific IgE and positive results for the intradermal test were observed for the 9 sensitized dogs after completion of the sesitization process. Sensitized dogs challenge exposed with hydrolyzed soy protein had a reduced inflammatory response after intradermal injection and no clinical response after an oral challenge exposure, compared with responses after intradermal and oral challenge exposure with native soy protein.

Conclusions and Clinical Relevance—Soy-sensitized dogs did not respond to oral administration of hydrolyzed soy protein. Thus, hydrolyzed soy protein may be useful in diets formulated for the management of dogs with adverse reactions to food.