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Source & spread of particulate & bacterial contamination between cattle during farm to abattoir phase of production
Project Code: M01009
Collis, V ; Davies, M;
Direct Laboratories Ltd
Division of Farm Animal Science, Department of Clinical Veterinary Science, University of Bristol,
Buncic, S; Reid, C;
SAC Veterinary Sciences Division
The objective of this study was to identify points in the farm to abattoir stages of beef cattle production where contamination by E. coli O157, Salmonella and Campylobacter may occur. The identification of control points and suitable intervention measures would then enable the development of an effective HACCP programme aimed at reducing the prevalence of bacterial pathogens on beef meat, with the ultimate objective of reducing levels of food-borne illness.
The incidence of E. coli O157, Salmonella and Campylobacter in beef cattle on farms in England/Wales and Scotland were investigated by the collection of faecal samples in both the autumn and spring seasons. E. coli O157 prevalence was 4% overall, but was higher in Scotland than England/Wales (P = 0.03). Campylobacter spp. prevalence was 18% overall, but was again significantly higher in Scotland (P < 0.001). Salmonella spp. levels were very low in both regions and averaged <0.2%. From information collected via a questionnaire, the risk factors that most influenced pathogen presence on-farm were:
- the total number of finishing animals on farm;
- the number of groups these cattle were kept in;
- the size of the groups of cattle closest to slaughter or sale;
- the presence of poultry on farm;
- the presence of gulls on silage pasture; and seasonal effects.
The spread of particulate and bacterial contamination between cattle during transport was investigated in two sub-objectives. The first involved mixing clean and dirty animals in transport, and highlighted the considerable increase in visible dirtiness of clean cattle after transporting with dirty cattle. A significant increase in bacterial levels was detected on wet animals following a period of rainfall (0.2 and 1.2 mm/hr during loading and unloading) (P <0.001). Overall higher bacterial levels were detected on dirty cattle, with the brisket consistently the most heavily contaminated part of the animal. The second sub-objective investigated the effect of the dry matter content of the diet that stock were fed (25%, 55%, 85%) and how this influenced cattle cleanliness after a 2.5 hour period of transport. Overall cattle that were fed low dry matter diets were visibly cleaner both pre- and post-transport, which is in contrast to previous findings, (P = 0.01) and had the lowest levels of both Enterobacteriaceae and E. coli (P = 0.02) when compared to cattle fed on higher dry matter diets. Levels of both Enterobacteriaceae and E. coli were significantly higher in autumn (P = 0.03).
To establish the incidence of contamination in cattle, and investigate bacterial spread between cattle in a livestock market environment, a survey was carried out of 6 livestock markets, which were visited during both the summer and winter seasons. E. coli O157 was present in 0.9 of pre-sale samples and 1.4% post-sale samples, while Campylobacter was present in 8% of samples and Salmonella was not detected. Higher bacterial levels were associated with:
- unclipped cattle, which had greater counts than partially and fully clipped cattle;
- lorries with straw bedding;
- low dry matter diets (in contrast to previous research);
- no diet change before sale;
- larger groups of animals (post-sale);
- mixing of groups (post-sale).
A higher Meat Hygiene Service (MHS) category (i.e. MHS 3, 4 and 5 unacceptable dirty animals that require cleaning up before slaughter) was associated with:
- larger groups of cattle (P = 0.01);
- unclipped cattle (P < 0.01) (91% in summer);
- cattle with 'curly' coats (P = 0.03) (48% in winter).
Overall higher MHS category was linked with a higher post-sale E. coli (P=0.02) and a higher overall Enterobacteriaceae level (P=0.008).
A simulated market study used harmless marker bacteria to determine pathogen movements through a typical livestock market. The results of this study showed that the market environment provided significant opportunities for the transfer of pathogens between animals. Direct transfer of marker bacteria between animals was confirmed in 33%, 17% and 47% of cases using three separate markers, introduced at different stages in the marketing process. Marker was also transferred from animals to environmental surfaces such as race surfaces. Environmental transfer was widespread because up to 89% of the surfaces sampled were positive for the marker organisms. Furthermore, transfer was higher in confined areas such as races and crushes where the risk of transfer from cattle hide would have been greater. The introduction of unfamiliar animals also increased the potential for transfer of marker.
To determine the extent of cattle hide, and lairage contamination within abattoir environments, the prevalence of food-borne pathogens E. coli O157, Salmonella spp., and Campylobacter spp. was determined in three commercial abattoirs. Hide contamination with E. coli O157 and Salmonella spp. was greater than detected in the lairage environment. The most frequently contaminated areas in lairage were the holding pen floors (50% +ve), the entrance to stun boxes (27.8% )ve) and the stun box floors (22% )ve).
The growth and survival of E. coli O157, Salmonella spp., and Campylobacter spp., on metal, painted metal, concrete straw and hide, surfaces commonly found in the cattle lairage, were investigated under warm or cold, wet or dry and clean or dirty conditions. The conditions investigated were selected from a range commonly associated with abattoirs. Pathogen survival was better in dirty samples (faeces) and on straw or hide, than on metal or concrete. Survival was also better in cold (10°C) than warm (25°C) conditions, and at high levels of relative humidity (96% RH). Survival of pathogens was shown to exceed 24 hours under these conditions, posing a high risk for cross contamination between animals processed on different days.
The spread of pathogens within cattle lairage, from animal-animal, from environment-animal, and animal-environment was investigated using harmless marker bacteria. Extensive cross-contamination occurred within lairage, and via transfer to and from environmental surfaces. The experiment highlighted a considerable risk of transfer of pathogens from the hide to the carcass at slaughter, and also the possibility of further cross-contamination of the finished carcass through standard slaughter procedures and equipment.
The influence of dietary measures on pathogen shedding and transfer was also investigated in an attempt to improve cleanliness and reduce bacterial load. The influence of an on-farm diet change on the mass of faeces excreted and the levels of bacteria shed into the excreta revealed that mean faecal dry matter output from a final hay diet was lower than that generated from a final compound diet. It was concluded that a diet change to hay may lead to lower dry matter faecal output, and there was some evidence that there was also an increase/fluctuation in the levels of total aerobes and E. coli that were shed.
A 'best' and 'worst' practice comparison was carried out. 'Best' practice animals were transported for a single 2.5 hour journey after which the levels of Enterobacteriaceae, E. coli and Total Viable Counts (TVC's) on hide had increased. There was no significant difference in bacterial levels on the hide of the Żworst' practice animals after a short journey of 1 hour. However, following a 2 hour period of penning E. coli and Entero. levels rose between 0.2-0.5 log CFU/cm2. Bacterial levels subsequently fell following mixing with unfamiliar animals in a strong sunlight, high temperatures, in the outdoor environment, but rose again (range 0.25-1.0 log CFU/cm2) following a further 2.5 hours in transport.
Results obtained from this study were developed to identify intervention strategies, which could be used as the basis of a hazard analysis and critical control point (HACCP)-type programme for the farm-to-abattoir phase of the production cycle. A generic Hazard Analysis and Critical Control Point (HACCP)-type scheme was produced that included the development of a flow chart for beef production, which included all of the main UK production systems for beef cattle. Processes and steps of the production cycle (e.g. birth, arrival, suckling, weaning/housing, grazing, finishing, transfer/transport, slaughter) were identified, and the associated risks and hazards were categorised. A summary sheet was produced that included an outline of general good hygiene practices, identification of control measures, their limitations, and appropriate monitoring procedures. A description of what corrective actions should be followed to restore control to the production system when problems occurred and effective recording procedures were also documented.
These investigations have provided evidence that certain measures can be undertaken in beef cattle production to aid in the reduction of food-borne pathogens reaching the carcass at slaughter.
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