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Routes of enteric microorganism contamination of beef and lamb carcasses and improved intervention measures

Project Code: M01006

30/06/2001

Silsoe Research Institute
Tinker, D ; Whyte, R;
University of Nottingham
Dodd, C; Johnson, S;
Division of Farm Animal Science, Department of Clinical Veterinary Science, University of Bristol,
Buncic, S; Reid, C

Background

Foodborne pathogens in meat products are generally associated with contamination by the gut contents and faeces of livestock. During raising on the farm, transport and lairage, there is ample opportunity for faeces to contaminate the outer surfaces of livestock. During dressing operations, transfer of microorganisms can occur from both gut and hide. There are several routes of transfer including aerosols, direct contact and indirect contact. There is also potential cross-contamination from other carcasses and sources in the abattoir.

Rationale and Objectives

The study was aimed at promoting food safety.

In the UK, the majority of lambs are processed at a rate of around 250-300/hour, the carcass dressing operations being carried out by around 25 operators. Cattle are processed at around 20-50/hour with around 20 operators

It is easy to see how various routes can form that allow contamination from the surface of the animal, or from the gut, to be passed onto the carcass. Direct contact between hide and carcass, many pieces of equipment, hands and bio-aerosols all provide routes.

Obvious routes have been tackled but there are still several where the route is indeterminate or its contribution is uncertain.

This project was to investigate some intervention procedures which are just coming into abattoirs to see how important they might be. The project would use tracer techniques to study the routes and determine how important they might be for carcass contamination. Both artificially introduced markers and molecular microbiology tracing techniques would be tried.

It was expected that the project would provide information on several aspects.
• It would indicate how useful molecular tracing would be for investigating the practical problems of microbial contamination in an abattoir;
• Bio-aerosols would be sampled to investigate where these might be important;
• Tracer techniques would allow some relatively new interventions to be investigated for effectiveness; and
• Systems and procedures would be studied to identify further the sources and plausible routes of carcass contamination.

Specific Objectives

This project aimed to:
• determine experimentally the sources and transmission routes associated with microbial contamination of carcasses during dressing,
• analyse relevant operations to propose practical intervention measures,
• identify, investigate and evaluate intervention measures including:
a) on-farm feed withdrawal to reduce faecal contamination of the hides,
b) improve sealing techniques to minimise release of gut contents, and
c) investigate the use of a system to remove faecal contamination.

Approach

The project was to involve the industry. Contacts were made with industry bodies and abattoirs which showed which new techniques were being introduced and where.

Before undertaking trials in abattoirs the team
a) held a forum with scientists and industry to find practical ways of sampling that could be used on a line but would provide good scientific evidence.
b) Undertake limited trials in research abattoirs to ensure that the sampling and analytical techniques would be satisfactory.

Visits were then made to two beef abattoirs and a lamb line at which samples were taken. The lamb line was initiating a new sealing technique and results were obtained both with and without the sealing. This plant was also considering a carcass cleaning technique and this was included in the research.

The foot and mouth outbreak caused severe disruption while this project was being undertaken.

Key Findings

Sheep abattoirs
• Bunging of sheep carcasses appears to be an effective intervention since postevisceration E. coli counts reduced by about 100 fold.
• Oesophageal sealing should be effective.
• The steam-vacuum unit is effective on sheep carcasses.
• In general fine bio-aerosols were not found in large numbers during hide/pelt removal implying that they are of minor importance.

Beef abattoirs
The results from the beef abattoirs followed the results for the lamb but there is some evidence that the hide removal could be improved.

Molecular typing was a useful technique but involved considerable effort within the laboratory and in taking detailed record of all the abattoir operations.

In some of the abattoirs the routes of contamination were often clear cut.

The results of the feed withdrawal study in cattle indicate that for 24h or 48h periods the number of total E. coli shed by cattle can increase significantly. However the gut pH
and certain bacterial groups are altered and for meat safety the results do not support fasting as an intervention measure

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