A longitudinal observational study of Salmonella shedding patterns by commercial turkeys during rearing and fattening,showing limitations of some control measures

1. The onset and progression of Salmonella infections was investigated in commercial turkey flocks from placement at 1 d old until slaughter in “brood and move” systems using a longitudinal observational approach based on faeces and environmental sampling with subsequent culture of Salmonella.

2. Persistent Salmonella Newport contamination was found within rearing houses and on their external concrete aprons after cleaning and disinfection between crops of heavily shedding young birds.

3. Salmonella shedding was often detected by 5 d of age and the frequency of positive samples peaked at 14–35 d. Thereafter Salmonella isolations declined, especially in the later (fattening) stages. Samples were still Salmonella-positive at low prevalence in half of the intensively sampled houses at slaughter age.

4. A number of management interventions to combat Salmonella infection of flocks, including sourcing policy, competitive exclusion cultures and cleaning and disinfection, were inadequate to prevent flock infection, although improved disinfection on one unit was associated with a delay in the onset of flock infection.

     

Selection of Swaledale sheep of reduced susceptibility to experimental scrapie

A flock of 294 Swaledale sheep was injected with brain tissue from different sources so as to include strains of natural scrapie currently affecting the Swaledale breed. Discounting intercurrent deaths, 85 per cent of the flock developed clinical scrapie within an observation period of 2557 days (seven years). Scrapie cases fell into distinct early and late groups, occurring at (mean +/- sem) 287 +/- 7 days and 1207 +/- 38 days after injection, respectively. Breeding groups were formed from the survivors after the early cases had occurred and successive lamb crops were produced. Two groups of progeny and two groups of controls were injected with scrapie. The incidence of scrapie in the progeny (27 per cent) was much lower than in the controls (64 per cent). The incidence in the progeny was also assessed in relation to the response of their parents: it was high (about 40 per cent) when one or both parents developed late scrapie but otherwise very low (about 5 per cent). Hence the progeny of surviving parents had a greatly reduced susceptibility to the strains of scrapie used. Seventy-two of these selected progeny formed a nucleus flock which is being bred at Redesdale. The next stage of the experiment is to assess the effect of selected rams in recorded flocks with a high incidence of natural scrapie.     

LAND RESTORATION WITH PULVERIZED FUEL ASH

This paper describes experiments carried out with different depths of topsoil and methods of cultivation on an ash lagoon at Besthorpe, near Newark. Good yields of grass were obtained even on bare ash with suitable rates of fertilizer application. In the conditions existing at Besthorpe, the optimum depth of soil appeared to be three in. (7.62 cm), but the depth of cultivation (three in. (7.62 cm) or twelve in. (30.48 cm), die latter resulting in mixtures of soil and ash, had no significant effect. B uptake by the growing plants was markedly lower in the third year of the experiment but, apart from its possible effect on yield, it produced no ill effects.     

The importance of sub‐peat carbon storage as shown by data from Dartmoor,UK

Peatlands are highly valued for their range of ecosystem services, including distinctive biodiversity, agricultural uses, recreational amenities, water provision, river flow regulation and their capacity to store carbon. There have been a range of estimates of carbon stored in peatlands in the United Kingdom, but uncertainties remain, in particular with regard to depth and bulk density of peat. In addition, very few studies consider the full profile with depth in carbon auditing. The importance of sub‐peat soils within peatland carbon stores has been recognized, but remains poorly understood and is included rarely within peatland carbon audits. This study examines the importance of the carbon store based on a study of blanket peat on Dartmoor, UK, by estimating peat depths in a 4 × 1 km survey area using ground penetrating radar (GPR), extraction of 43 cores across a range of peat depth, and estimation of carbon densities based on measures of loss‐on‐ignition and bulk density. Comparison of GPR estimates of peat depth with core depths shows excellent agreement, to provide the basis for a detailed understanding of the distribution of peat depths within the survey area. Carbon densities of the sub‐peat soils are on average 78 and 53 kg C/m³ for the overlying blanket peat. There is considerable spatial variability in the estimates of total carbon from each core across the survey area, with values ranging between 56.5 kg C/m² (1.01 m total depth of peat and soil) and 524 kg C/m² (6.63 m total depth). Sub‐peat soil carbon represents between 4 and 28 per cent (mean 13.5) of the total carbon stored, with greater values for shallower peat. The results indicate a significant and previously unaccounted store of carbon within blanket peat regions which should be included in future calculations of overall carbon storage. It is argued that this store needs to be considered in carbon audits.     

The re-expansion and improving status of the silver-spotted skipper butterfly (Hesperia comma) in Britain: a metapopulation success story

Many specialist species are declining as a result of habitat loss and fragmentation, such that conservation actions typically aim to stem rates of decline rather than bring about genuine recovery. Here, we document the recovery of a species from former population refuges. An extensive survey of the entire British range of Hesperia comma, conducted in 2000, recorded over three times the number of tetrads (2 km × 2 km grid squares) occupied in 1982. This was accompanied by a fourfold increase in the number of populations and a 10-fold increase in the habitat area occupied. The improving status of H. comma is the product of good habitat management, recovering rabbit populations and climate warming, which have improved the quality, and increased the availability, of suitable habitat. This has enabled remnant metapopulations to expand, via distance-dependent colonisation, through large networks of habitat. Metapopulation recovery in H. comma demonstrates that landscape-scale conservation can be successful.     

Spatial and Seasonal Variations in Nitrogen Leaching and Acidity across Four Acid-impacted Regions of the UK

This study examines the seasonal variability in levels of nitrogen (N) leaching and acidity in four acid impacted upland regions of the UK: the South Pennines, Snowdonia, Galloway and the Mourne Mountains. All regions are acidified, with median pH values of <5.5. The South Pennines exhibit excess sulphate concentrations an order of magnitude higher than those for other regions and have the lowest pH values of all the regions. Nitrate concentrations are highest in the South Pennines (seasonal medians 20–26 μeq l^?1) and the Mourne Mountains (seasonal medians 9–26 μeq l^?1). Surface water in the Mourne Mountains is the most highly N impacted in terms of the proportional contribution of N to acidity. All N species exhibit seasonality, with greater retention by catchment soils and vegetation in August. This seasonality is most marked in Snowdonia and least marked in the South Pennines. This implies that the South Pennines have reached an advanced stage of N saturation. Despite the reductions in S deposition, xSO₄ is the dominant anion for all sites in the South Pennine and Snowdonia regions. A strong negative relationship between the contribution of NO₃ to total acidity and DON was observed for all regions except the South Pennines. It is hypothesized that catchments dominated by organic rich soils produced more DON and have an increased capacity to immobilise NO₃. Seasonal nitrogen budgets show that over 60% of the N inputs are retained within catchments, and no site retains all incoming N throughout the year.     

Spatial and temporal variations in the erosion threshold of fine riverbed sediments

Purpose

Lowland chalk streams in the UK are experiencing increased deposition of fine sediment due to changes in land-use practices, channel modifications, and groundwater abstraction. The excessive fine sediment deposits have been linked to benthic habitat degradation, the obstruction of surface?Cgroundwater flow, and the storage of contaminants, such as nutrients and pesticides. While research has been conducted on the provenance, transport, deposition, and storage of fine sediment in chalk streams, none has expressly investigated the erosion of fine sediment deposits.

Materials and methods

A year-long field survey was conducted in two reaches of the Frome-Piddle catchment (Dorset, UK) to quantify spatial and temporal variations in the erosion thresholds of surficial fine sediment deposits. Erosion thresholds were measured at randomly located points within areas of sediment accumulation using a cohesive strength meter (CSM). The threshold measurements were paired with sediment cores for analysis of the physical, chemical, and biological properties of the sediment. Spatial and temporal patterns in the erosion thresholds of fine sediment were analyzed using nonparametric statistical tests and visualized with GIS. The sediment properties underlying the variations in erosion thresholds were examined through correlation and linear regression analyses.

Results and discussion

Erosion thresholds varied significantly over space and time within the stream reaches. Erosion thresholds were greater for fine sediment deposits found in the center of the channel than in the margins. Thresholds were highest in September 2008 and declined substantially to a minimum in May 2009, with a small peak in March 2009, indicating an annual cycle in erosion thresholds. Effective particle size was identified statistically as the most important sediment property influencing erosion thresholds and was probably underlying much of the spatial variation within the reaches. None of the measured sediment properties adequately characterized the temporal variation in erosion thresholds, however, the results suggest that biological sediment properties and water geochemistry (i.e., cation content) may play a role.

Conclusions

By identifying significant spatial and temporal variations in erosion thresholds, this study provides valuable information on the stability of fine sediment deposits, and sediment-bound contaminants, in lowland river systems. This is a crucial step in assessing their local environmental impacts and developing models of fine sediment transport for the effective management of catchment sediment budgets and water resources.     

Evidence from tag recapture experiments that fish learn to avoid fishing gear

We found evidence that tagging induced trap shyness in snapper (Pagrus auratus), i.e., tagged fish had a reduced probability of recapture by the method by which they had originally been caught. Tagging experiments in 1985 and 1994 involving single release over a short period and single recapture were conducted on a closed population (SNA 1: East Northland-Hauraki Gulf-Bay of Plenty). Initial capture was by trawling and by line fishing, while recapture over an extended period included other methods. A test for trap shyness that removed the possible effects of spatial and fish size heterogeneity gave a significant result for both years. The data suggested that the trap shyness effect might have been smaller for trawl-released fish than for line-released fish. However, we estimated a single trap shyness factor (0.71). There was also some evidence for attenuation of trap shyness over time.     

Partial resistance to Erysiphe graminis hordei in old European barley varieties

Summary A collection of 133 genotypes consisting mainly of old European barleys and land varieties was assessed for level of partial resistance to barley mildew at the adult plant stage. Identification of any known resistance factors conferring hypersensitive reactions to the mildew races present at various frequencies in N.W. Europe was ensured through seedling tests with an appropriate AO mildew isolate.Thirty-nine varieties with relatively high levels of adult (partial) resistance and lacking known race-specific resistance genes were tested over a period of three years in field disease nurseries. At least thirteen varieties showed significantly less percentage leaf area infected than the control variety Proctor. These constitute a useful reserve of non-hypersensitive resistance, probably under the control of genes with mainly additive effects. In combination, these genes give enhanced levels of resistance, which could be of a more stable nature.