Silsoe Research Institute

Selected ion flow tube mass spectrometry, SIFT-MS, has been used to monitor the volatile compounds in the exhaled breath of 30 volunteers (19 males, 11 females) over a 6 month period. Volunteers provided breath samples each week between 8:45 am and 1 pm (before lunch), and the concentrations of several trace compounds were obtained. In this paper the focus is on ammonia, acetone and propanol. It was found that the concentration distributions of these compounds in breath were close to log-normal. The median ammonia level estimated as a geometric mean for all samples was 833 parts per billion (ppb) with a multiplicative standard deviation of 1.62, the values ranging from 248 to 2935 ppb. Breath ammonia clearly increased with increasing age in this volunteer cohort. The geometric mean acetone level for all samples was 477 parts per billion (ppb) with a multiplicative standard deviation of 1.58, the values ranging from 148 to 2744 ppb. The median propanol level for all samples was 18 ppb, the values ranging from 0 to 135 ppb. A weak but significant correlation between breath propanol and acetone levels is apparent in the data. The findings indicate the potential value of SIFT-MS as a non-invasive breath analysis technique for investigating volatile compounds in human health and in the diseased state.

Abstract Nitate retention in riparian buffer strips is well documented in summer periods, but the potential of winter retention within these zones is poorly documented. Two sites, grass ( Lolium perenne L.), and poplar ( Populus italica )‐vegetated riparian strips, were investigated in southern England (River Leach). Groundwater flow was via subsurface pathways within the sites, NO − 3 concentration gradients and loading rates were calculated over the winter period. Nitrate retention was found to be linearly dependent on load rate. Nitrate retention occurred at the edge of the riparian zone. This was most obvious in the poplar site where all hillslope‐derived NO − 3 was absorbed within the first 5 m of flow within the riparian strip. When loading rates into the sites increased, NO − 3 absorption migrated upslope from the riparian site. The poplar‐vegetated riparian zone was found to be more resilient (99% retention of NO − 3 ) than the grass‐vegetated riparian zone (84% retention of NO − 3 ) in the winter months. It is postulated that although vegetation has no active role in retaining NO − 3 in the winter, above‐ground vegetative biomass does contribute C to the soil microbacterial biomass that is engaged in NO − 3 reduction in the winter months, this accounted for the greater efficiency of the poplar vegetated site.

Life-history theory proposes that costs must be associated with reproduction. Many direct costs are incurred during breeding. There is also evidence for indirect costs, incurred after breeding, which decrease survival and future reproductive success. One possible indirect cost identified in birds is that breeding activity in some way compromises plumage quality in the subsequent moult. Here we propose a mechanism by which this could occur. Breeding activity delays the start of moult. Birds that start to moult later also moult more rapidly--an effect of decreasing daylength. Could this result in poorer quality plumage? We kept two groups of male European starlings, Sturnus vulgaris, one on constant long days and the other on decreasing daylengths from the start of moult. Decreasing daylengths reduced the duration of moult from 103 +/- 4 days to 73 +/- 3 days (p < 0.0001). Newly grown primary feathers of birds that moulted fast were slightly shorter, weighed less (p < 0.05) and were more asymmetrical. They had a thinner rachis (p < 0.005), were less hard (p < 0.01) and less rigid (p < 0.05). They were also less resistant to wear so that differences in mass and asymmetry increased with time. There was no difference in Young's modulus. Poorer quality plumage will lead to decreased survival due to decreased flight performance and increased thermoregulatory costs. Thus, reproduction incurs costs through a mechanism that operates after the end of breeding.

SUMMARY Time‐domain reflectometry (TDR) is becoming an increasingly popular technique for measuring soil water content. It is based on measuring the dielectric constant of soil from the propagation velocity of a pulse travelling along an electromagnetic transmission line embedded in the soil. Although various designs of transmission line have been proposed, there have been no attempts to contrast these designs to enable the experimenter to select an appropriate system. A second area which needs consideration is the choice of calibration function, as the use of an empirical calibration with no physical basis persists. In this paper, transmission line design (balanced and unbalanced) is discussed and a simple linear calibration function based on refractive index is developed.

Abstract. The operational system known as MORECS which provides estimates of evaporation, soil moisture deficit and effective precipitation under British climatic conditions has been revised as version 2.0. An overview of the new system is described with emphasis on the new additions. The major changes from the older version (Thomson, Barrie and Ayles, 1981) include the introduction of the crop oil-seed rape, a revised treatment of soils and available water capacity and a land use data base which is representative of the 1990s.

The study aimed to identify sources of campylobacter in 10 housed broiler flocks from three United Kingdom poultry companies. Samples from (i) the breeder flocks, which supplied the broilers, (ii) cleaned and disinfected houses prior to chick placement, (iii) the chickens, and (iv) the environments inside and outside the broiler houses during rearing were examined. Samples were collected at frequent intervals and examined for Campylobacter spp. Characterization of the isolates using multilocus sequence typing (MLST), serotyping, phage typing, and flaA restriction fragment length polymorphism typing was performed. Seven flocks became colonized during the growing period. Campylobacter spp. were detected in the environment surrounding the broiler house, prior to as well as during flock colonization, for six of these flocks. On two occasions, isolates detected in a puddle just prior to the birds being placed were indistinguishable from those colonizing the birds. Once flocks were colonized, indistinguishable strains of campylobacter were found in the feed and water and in the air of the broiler house. Campylobacter spp. were also detected in the air up to 30 m downstream of the broiler house, which raises the issue of the role of airborne transmission in the spread of campylobacter. At any time during rearing, broiler flocks were colonized by only one or two types determined by MLST but these changed, with some strains superseding others. In conclusion, the study provided strong evidence for the environment as a source of campylobacters colonizing housed broiler flocks. It also demonstrated colonization by successive campylobacter types determined by MLST during the life of a flock.

Summary The standard estimator of the variogram is sensitive to outlying data, a few of which can cause overestimation of the variogram. This will result in incorrect variances when estimating the value of a soil property by kriging or when designing a sampling grid to map the property to a required precision. Several robust estimators of the variogram, based on location and scale estimation, have been proposed as improvements. They seem to be suitable for analysis of soil data in circumstances where the standard estimator is likely to be affected by outliers. Robust estimators are based on assumptions about the distribution of the data which will not always hold and which need not be made in kriging or in estimating the variogram by the standard estimator. The estimators are reviewed. Simulation studies show that the robust estimators vary in their susceptibility to moderate skew in the underlying distribution, but that the effects of outliers are generally greater. The estimators are applied to some soil data, and the resulting variograms used for ordinary kriging at sites in a separate validation data set. In most cases the variograms derived from the standard estimator gave kriging variances which appeared to overestimate the mean squared error of prediction (MSEP). Kriging with variograms based on robust estimators sometimes gave kriging variances which underestimated the MSEP or did not differ significantly from it. Estimates of kriging variance and the MSEP derived from the validation data were generally close to estimates from cross‐validation on the prediction set used to derive the variograms. This indicates that variogram models derived from different estimators could be compared by cross‐validation.

Atmospheric ammonia is a major aerial pollutant of poultry buildings. The current exposure limits for ammonia of 25 ppm are set on the basis of human safety rather than animal welfare. This paper reviews the evidence for ammonia exposure affecting various aspects of poultry welfare. The reviewed evidence suggests that ammonia exposure (1) causes irritation to the mucous membranes in the eyes and the respiratory system; (2) can increase the susceptibility to respiratory diseases; and (3) may affect food intake, food conversion efficiency and growth rate. The behavioural effects of ammonia on poultry have recently been investigated and suggest that there may be a threshold for ammonia detection or aversion at or below the current exposure limit. The available evidence for the effects of ammonia on poultry welfare should be considered when setting future guidelines for ammonia exposure in poultry houses.

Data from the Woburn Erosion Reference Experiment (Bedfordshire, UK) were used to test the hypothesis that losses of phosphorus (P) in small erosion events are as great as those in infrequent large events, and to examine the effect of storm characteristics on the selective enrichment of P in eroded sediment. For almost every plot event in the period 1988 to 1994, the clay-sized fraction of the sediment was enriched compared with the soil of the plots. There was more variation in clay enrichment for smaller erosion events than for larger ones. The clay and P contents of the sediment were strongly correlated (p < 0.01), and there was a wider range of P concentrations in the sediment derived from small events than in that from large events. However, individual events resulting in small soil losses (< 100 kg) did not account for greater P losses than larger events (> 100 kg). The greater frequency of smaller events, combined with the likelihood of higher P concentrations in the sediment, therefore accounted for a greater proportion of the P lost over the 6-yr period than the infrequent large events. Phosphorus concentrations generally increased with increasing peak discharge and decreased with increasing event duration. For the same return period, P losses were generally greater from plots cultivated up and down the slope than from those cultivated across the slope. Overall, our results suggest that small erosion events should be controlled to prevent P contamination of surface waters and that the most effective means of doing this are by the introduction of minimal tillage techniques and across-slope cultivations.

1. The spectral sensitivity of 7 broiler fowl was determined in a behavioural test. 2. Initially the birds were trained to receive a food reward by pecking at a clear, Perspex panel behind which was a light stimulus (circular, diameter = 9 mm), originating from a tungsten-halogen lamp. Subsequently, they were trained to choose between 2 panels only 1 of which was lit; the assignation of light and dark on each panel was randomly ascribed between trials. The colour of the lit panel was determined by the wavelength of the light transmitted through one of 13 closely defined narrow bandwidth filters between 326<lambda<694 nm. The flux of photons and hence the intensity of the stimulus received by the bird could be controlled by changing the voltage across the lamp. The photon flux was gradually reduced until the birds failed to detect accurately the lit panel. Success was defined as a choice of the lit panel 9 or more times in a sequence of 10 trials, providing that the sequence contained at least 4 changes in the position of the stimulus. 3. Generally, the birds showed a peak sensitivity between 540<lambda<577 nm. The results agree with electrophysiological data between 507<lambda<694 nm and psychophysical data between 500<lambda<700 nm but our data showed higher sensitivities between 380<lambda<507 nm compared with electro-physiological findings. 4. Our findings confirm that broilers can 'see' into the UV(A) range and that their spectral sensitivity is different to the human. The implication of this is that the measurement of light intensity in poultry housing using the lux unit does not accurately describe the intensity perceived by fowl. 5. Experimenters using colour, for example differently coloured lighting or food, need to account for this different sensitivity when interpreting their results.

Abstract The effectiveness of power ultrasound for the microbial decontamination of minimally processed fruits and vegetables was studied. Reductions in Salmonella typhimurium attached to iceberg lettuce obtained by cleaning with water, chlorinated water, ultrasound with water and ultrasound with chlorinated water were 0.7, 1.7, 1.5 and 2.7 logs, respectively, for small-scale (2 L) trials. The cleaning action of cavitation appears to remove cells attached to the surface of fresh produce, rendering the pathogens more susceptible to the sanitizer. For large-scale (40 L) trials, the addition of chlorine to water in the tank gave a systematic difference in Escherichia coli decontamination efficiency. However, the frequency of ultrasound treatment (25, 32–40, 62–70 kHz) had no significant effect on decontamination efficiency (P &amp;gt; 0.69). With the potentially high capital expenditure together with the expensive process of optimization and water treatment, it is unlikely that the fresh produce industry would be willing to take up this technology. Furthermore, the additional one log reduction achieved by applying ultrasound to a chlorinated water wash does not completely eliminate the risk of pathogens on fresh produce.

Summary The physical characteristics of the soil at the root–soil interface are crucial because they determine both physical aspects of root function such as water and nutrient uptake and the microbial activity that is most relevant to root growth. Because of this we have studied how root activity modifies the structure and water retention characteristic of soil adjacent to the root for maize, wheat and barley. These plants were grown in pots for a 6‐week growth period, then the soil adjacent to the root (rhizosphere soil) and bulk soil aggregates were harvested. These soil aggregates were then saturated and equilibrated at matric potentials between −600 kPa and saturation, and the water retention characteristics were measured. From subsamples of these aggregates, thin sections were made and the porosity and pore‐size distributions were studied with image analysis. Both image analysis and estimates of aggregated density showed that the rhizosphere soil and bulk soil had similar porosities. Growing different plants had a small but significant effect on the porosity of the soil aggregates. Image analysis showed that for all the plant species the structure of the rhizosphere soil was different to that of the bulk soil. The rhizosphere soil contained more larger pores. For maize and barley, water retention characteristics indicated that the rhizosphere soil tended to be drier at a given matric potential than bulk soil. This effect was particularly marked at greater matric potentials. The difference between the water retention characteristics of the bulk and rhizosphere soil for wheat was small. We compare the water retention characteristics with the data on pore‐size distribution from image analysis. We suggest that differences in wetting angle and pore connectivity might partly explain the differences in water retention characteristic that we observed. The impact of differences between the water retention properties of the rhizosphere and bulk soil is discussed in terms of the likely impact on root growth.

1. A survey of the concentration and emission rates of aerial ammonia, nitrous oxide, methane, carbon dioxide, dust and endotoxin was undertaken in 4 examples each of typical UK broiler, cage and perchery houses over 24 h during winter and summer. 2. Overall the air quality within the poultry houses was unsatisfactory as judged by the dual criteria of farmer health and bird performance. 3. Mean concentrations of ammonia ranged from 12.3 to 24.2 ppm while concentrations of methane and nitrous oxide were close to ambient levels. Mass concentrations of aerial dust ranged from 2 to 10 mg/m3 and 0.3 to 1.2 mg/m3 for inspirable and respirable fractions respectively, while endotoxin concentration was typically about 0.1 microgram/m3 (inspirable fraction). 4. Emission rates of gaseous ammonia were rapid (9.2 g (NH3)/h per 500 kg live body weight) and uniform across the three types of building, while emissions of methane and nitrous oxide were slow. Rates of dust emission ranged from 0.86 to 8.24 g/h per 500 kg live body weight in the inspirable size fraction.

Abstract The sensitivity of modelled northern hemisphere climate to modification of the snow‐covered surface albedo is investigated using the United Kingdom Meteorological Office (UKMO) general circulation model (GCM). the UKMO GCM is a global, primitive‐equation model with 11 layers in the atmosphere. Surface processes in the model are highly parametrized, with bulk aerodynamic formulation of the surface fluxes and a ‘bucket’ soil‐moisture accounting method. the experiment represents in a highly simplified fashion the role of the boreal forests in reducing the surface albedo under snow‐covered conditions. A parametrization of snow‐covered land was developed which allows the maximum albedo attainable with a snow cover to be prescribed as a function of vegetation type. In the standard version of the model the maximum snow‐covered surface albedo attainable is 0.60, which exceeds observed values for the forested areas of the northern hemisphere. the model was integrated twice, with different albedos representing forested and deforested conditions. the sensitivity of the heat and hydrologic budgets for the northern hemisphere and deforested areas is discussed. A detailed analysis of the deforested regions reveals systematic reductions in temperature of up to 2.8 K. Precipitation shows a systematic decrease in the affected regions. the largest decreases occur generally in the months with largest evaporation changes. For the case of no masking by forest vegetation (equivalent to boreal deforestation) the model produces a significant change in the pattern of snow‐melt. the removal of forest affects both the magnitude and the timing of spring snow‐melt, and consequently also the runoff. There are delays in snow‐melt‐induced runoff peaks by a month and increases in the magnitudes by on average 32%. the role of large‐scale advection is investigated by comparison with the results from a single‐column‐model experiment. A realistic representation of the snow‐covered surface albedo is evidently a requirement for simulations of the northern hemisphere climate.

The effects of environmental conditions and mechanical damage on the tensile stiffness and strength of two natural fibers, flax and nettle, are investigated. Flax and nettle both contain cellulosic fiber bundles in the outer layer of the plant, each bundle comprising many individual cells bonded together. Novel experimental equipment is designed and constructed to measure, under varying environmental conditions, the static and dynamic tensile moduli and the strength of individual fiber cells. As previous work has shown, the tensile modulus is dependent on environ mental relative humidity, but the effect of fiber damage is also significant. There is a correlation between the extent of damage, measured as the proportion of the fiber showing as bright under a polarizing microscope, and the modulus. When the effect of damage is taken into account, there is a consistent relationship between modulus and relative humidity.

Citrate is a normal constituent of milk that affects milk-processing characteristics. It is an intermediate in the tricarboxylic acid cycle and plays an indirect role in fat synthesis by providing reducing equivalents in the form of NADPH. The objective of this study was to investigate variation in citrate with stage of lactation and de novo fatty acid synthesis, without confounding dietary effects. Twenty-four cows were fed the same diet, and milk citrate and fatty acids were determined over a 10-d period. Eight cows were in early lactation [13 +/- 1.8 d in milk (DIM; mean +/-standard error], 8 in midlactation (130 +/-4.6 DIM), and 8 in late lactation (283 +/-3.4 DIM). For cows in early, mid, and late lactation, milk yield was 34.4, 34.4, and 21.4 L/d [standard error of difference (SED) 1.78]; milk fat was 50.4, 40.3, and 41.4 g/L (3.68); milk citrate was 11.3, 9.7, and 10.1 mmol/L (0.64); the ratio of 4-14 C:18-20 C fatty acids was 0.9, 1.3, and 1.2 (0.07). Activity of the fatty acid synthase enzyme system (EC 2.3.1.85) was calculated as acetate used for chain elongation (ACE); ACE (mol/d) for cows in early, mid, and late lactation, was 7.3, 11.1, and 8.1 (SED 1.05). For individual cows, citrate (mmol/L) = 14.3 -0.44 xACE (r2 = 0.58). We propose that ACE provides a more accurate indication of synthase activity than do fatty acid ratios or yields. This study confirms the hypothesis that variation in milk citrate with stage of lactation is related to de novo synthesis of fatty acids and that the relationship is independent of diet and milk yield.

Summary The weakest link between particles or aggregates determines the strength of soil. We have re‐examined the theory and, as a result, have re‐defined friability, F , as the coefficient of variation of soil tensile strength. The formal relationship between the parameter 1/α of the weakest link theory of strength, which has previously been used as a measure of friability, and the newly defined measure, F , is described by a simple equation which has an accuracy of within 2% over the range of interest. The quantity F is used to show that friability reaches maximum at water contents around the lower plastic limit, that mechanical disturbance of wet soil by tillage reduces the friability, and that friability is strongly positively correlated with the organic carbon content of the soil. These results show the merit of measuring friability for determining the optimum water content for tillage, for quantifying the damage done by different tillage practices, and as a theoretically based index of soil physical quality.

Abstract The visual system of domestic poultry evolved in natural light environments, which differ in many respects from the artificial light provided in poultry houses. Current lighting systems are designed mainly around human vision and poultry production, ignoring the requirements of poultry vision and the functional development of visual abilities during rearing. A poor correlation between the light provided and that required for effective vision may influence visually mediated behaviours such as feeding and social interaction, leading to distress and poor welfare. To understand fully the impact of the light environment on the behaviour and welfare of domestic poultry we need (i) to measure the physical properties of the light environment in a standard and relevant manner; (ii) to identify the limits of visual abilities in various light environments; (iii) to determine how light environments during rearing may disrupt the functional development of vision; and (iv) to resolve how visual abilities and lighting interact to affect visually mediated behaviour. Some conclusions can be drawn about the impact of current lighting regimes on bird welfare but there remains a pressing need to resolve various issues in this interaction. We propose, first, that dark periods should have a minimum duration of six hours; second, that bright light should be used in cases where pecking damage and cannibalism do not pose a problem; and third, that it is unlikely that the 100 Hz flicker associated with fluorescent light can be perceived by poultry. With less certainty, we can suggest that ultraviolet-supplemented lighting may have some welfare benefits, and that very dim lighting may adversely affect ocular development. We can only speculate on other issues, such as preferences and motivations for different coloured lighting or the ways in which lighting affects recognition of conspecifics. Several organisations and authorities have issued guidelines for poultry house lighting that strive to safeguard welfare and that are consistent with our current, but limited, understanding. One omission is a standard system for measuring light levels in poultry houses. Illumination with natural daylight would be an ideal solution to many lighting problems. Although some systems require artificial lighting for production purposes, we argue that it may be possible to rear birds humanely in artificial environments that contain some features of natural light. These features should be those for which poultry show some motivation, or whose exclusion would damage visual development.

Summary Variograms of soil properties are usually obtained by estimating the variogram for distinct lag classes by the method‐of‐moments and fitting an appropriate model to the estimates. An alternative is to fit a model by maximum likelihood to data on the assumption that they are a realization of a multivariate Gaussian process. This paper compares the two using both simulation and real data. The method‐of‐moments and maximum likelihood were used to estimate the variograms of data simulated from stationary Gaussian processes. In one example, where the simulated field was sampled at different intensities, maximum likelihood estimation was consistently more efficient than the method‐of‐moments, but this result was not general and the relative performance of the methods depends on the form of the variogram. Where the nugget variance was relatively small and the correlation range of the data was large the method‐of‐moments was at an advantage and likewise in the presence of data from a contaminating distribution. When fields were simulated with positive skew this affected the results of both the method‐of‐moments and maximum likelihood. The two methods were used to estimate variograms from actual metal concentrations in topsoil in the Swiss Jura, and the variograms were used for kriging. Both estimators were susceptible to sampling problems which resulted in over‐ or underestimation of the variance of three of the metals by kriging. For four other metals the results for kriging using the variogram obtained by maximum likelihood were consistently closer to the theoretical expectation than the results for kriging with the variogram obtained by the method‐of‐moments, although the differences between the results using the two approaches were not significantly different from each other or from expectation. Soil scientists should use both procedures in their analysis and compare the results.

Selected-ion flow-tube mass spectrometry (SIFT-MS) has been used to monitor the volatile compounds in the exhaled breath of 30 volunteers (19 male, 11 female) over a 6-month period. Volunteers provided breath samples each week between 8:45 and 13:00 (before lunch), and the concentrations of several trace compounds were obtained. In this paper the focus is on ethanol and acetaldehyde, which were simultaneously quantified by SIFT-MS using H3O+ precursor ions. The mean ethanol level for all samples was 196 parts-per-billion (ppb) with a standard deviation of 244 ppb, and the range of values for breath samples analysed is 0 to 1663 ppb. The mean acetaldehyde level for all samples was 24 ppb with a standard deviation of 17 ppb, and the range of values for breath samples analysed is 0 to 104 ppb. Background (ambient air) levels of ethanol were around 50 ppb, whereas any background acetaldehyde was usually undetectable. Increased ethanol levels were observed if sweet drink/food had been consumed within the 2 h prior to providing the breath samples, but no increase was apparent when alcohol had been consumed the previous evening. The measured endogenous breath ethanol and acetaldehyde levels were not correlated. These data relating to healthy individuals are a prelude to using breath analysis for clinical diagnosis, for example, the recognition of bacterial overload in the gut (ethanol) or the possibly of detecting tumours in the body (acetaldehyde).