Project title:    Cleaning and Disinfection of lairage-to-stunning areas in abattoirs.

Duration:         1st November 2003 - 31st October 2005

Background and Objectives

The aim of this study was to enable the identification of “common lairage practices” and to assess the general status of the lairage hygiene and lairage cleaning effectiveness in UK slaughterhouses.

Approaches

A survey of a large number of UK abattoirs was conducted via a questionnaire designed to obtain information on:

i) throughput and species slaughtered.

ii) construction materials used.

iii) use and type of bedding.

and

iv) details of cleaning/sanitation regimes. 

A representative group of abattoirs were selected on the basis of the responses to the questionnaire and the lairage at these plants investigated through enumeration of Escherichia coli remaining after routine cleansing operations.

The results of these visits showed that the E. coli indicator was not completely removed from abattoir lairages by standard cleaning practices.  Thus lairages may allow a risk of transfer of contamination from one processing day to the next.  Potentially, bacteria such as Salmonella may be transferred to the outer surfaces of animals held in the lairage facilities, and the skin or hide is a significant source of microbial contamination on the red meat carcasses subsequently produced.  To determine if this was the case, a second round of plant visits collected samples (n=556) from lairages and red meat carcasses (n=1050) in commercial abattoirs in the South-West of England.  The samples were tested for the presence of Salmonella spp.  6.5% of lairage samples were positive, containing estimated numbers of up to 10⁴ Salmonellae per sample.  Of carcass samples, Salmonella spp. was found on 9.6% of lamb carcasses, 12.7% of beef carcasses, 31% of pig carcasses, 20% of bobby calf carcasses and no cull cow/bull carcasses.  Subtyping divided the 137 isolates into seven serogroups and three PFGE clusters, and sensitivity testing against a bank of 16 antimicrobials indicated that 47 isolates had resistance to one or more antimicrobial agents.  These results indicate that routine cleansing measures in commercial abattoirs are insufficient to remove Salmonella contamination from the lairage environment, and the incidence of Salmonella spp. on red meat carcasses is quite high, although the implications of residual lairage contamination on carcass meat microbiology are not clear from this study.  Slaughterhouse operators should take steps to reduce the level of contamination both in their premises and on their carcasses.

What it means and why it's important

The study showed that microbial contamination often remains in UK lairage holding pens after routine cleaning operations.  It would appear that there are significant differences in the effectiveness of lairage cleaning programmes at commercial abattoirs, and that the stun-box-roll-out areas are often cleaned to a better standard than the holding areas.  As a result, there is a possible the risk of foodborne pathogens persisting in the environment and potentially contaminating animals and carcasses processed on subsequent days.