M01006: Routes of enteric micro-organism contamination of beef and lamb carcasses and improved intervention measures

Study Duration: July 1998 to June 2001

Contractor: Silsoe Research Institute

This project was commissioned to investigate ways to reduce micro-organism contamination of beef and lamb carcasses. This study compares changes in procedures, slaughterhouse environment and facilities, and their impact (pathogenic and non-pathogenic micro-organisms) of carcasses. It examines the routes of enteric microorganism contamination of beef and lamb carcasses and investigates intervention measures for reducing contamination.

The completion of this project was delayed due to the Foot and Mouth disease outbreak.

Microbiological surveys

Two microbiological surveys were conducted at separate lamb and beef slaughterhouses. At selected stages of carcass dressing, microbiological samples were taken from sites on the carcass, plant operators, fomites (materials and utensils likely to be a source of contamination) and from the air. Bacterial enumeration was conducted for total aerobic count (TAC), coliform count (CC) and E. coli count.

After a procedural change, a similar survey was undertaken on the dressing line of the lamb slaughterhouse. The results demonstrated that handling practices during dressing are a major cause of carcass contamination with enteric bacteria. In addition, enteric bacteria can also become widely dispersed via aerosols within the abattoir. However, the levels recorded were low and therefore probably do not represent a major source of carcass contamination. A procedure known as 'bunging' was shown to be a significant intervention measure for reducing the contamination of sheep carcasses with enteric bacteria.

Feed withdrawal trial

This trial on beef cattle involved the use of an E. coli marker (K12) to investigate pre-slaughter controls of carcass contamination through the withdrawal of feed for periods before slaughter. The transmission of the ingested marker organism was monitored in the faeces, during feed withdrawal periods; then in the guts and on the hide and carcass; and in the air during dressing. No marker organism was found to be airborne, but marker E. coli was detected on the hide, guts and on the carcass in low numbers during dressing.

Feed withdrawal for 24 or 48 hours significantly increased counts of E. coli in the faeces. Higher counts of E. coli were also found in the rumen of fasted cattle at slaughter. The results indicate that feed withdrawal may increase levels of pathogens such as E. coli in the faeces and guts of animals presented for slaughter and therefore do not support fasting as an intervention measure.

Steam-vacuum carcass cleaning as an intervention measure

The effectiveness of this carcass cleaning system to reduce 'hot spots' of physical and microbiological contamination on lamb carcasses was assessed in a lamb slaughterhouse. A pilot study indicated that the equipment was easy to use, caused little disruption to routine procedures and gave important reductions in total aerobic and coliform counts.

A larger scale study subsequently confirmed that the system could significantly reduce bacterial numbers. This process may offer a practical system for the on-line reduction of microbiological load on carcasses.

Pelt removal

Experiments were carried out to investigate methods of reducing contamination of lamb carcasses in low throughput abattoirs, where Cradle dressing is normally employed. Cradle design and pelt removal procedures were investigated, and a new method was developed for assessing gross visible contamination.

Significant improvements in microbiological and gross visible contamination (p<0.01) were achieved by procedural changes only; modifications to the cradle design had no effect. Additionally two improved methods, the 'Frame' and the 'Hybrid' system, of pelt removal and the effect of hand washing prior to carcass contact during the pelt removal procedure were investigated.

The results showed that both the Hybrid and Frame systems had significantly less microbiological and gross visible contamination (p<0.01) compared to the conventional Cradle design.

Final report is available from the Agency's Information centre.
To obtain a copy, please contact the Enquiry Desk, Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: infocentre@foodstandards.gsi.gov.uk).

The following research papers have also been published:

Whyte R.T., Holder J.S., Tinker D.B., Allen V.M., White R.P. and Hinton M.H. Assessment and Development of Procedures and Apparatus To Reduce Contamination of Lamb Carcasses during Pelt Removal in Low-Throughput Abattoirs. Journal of Food Protection 65 (1): 41-49.

Reid C.A., Avery S.M., Warriss P. and Buncic S. The Effect of Feed Withdrawal on Escherichia coli shedding in beef cattle. Food Control 13 (6-7): 393-398.

Contact: For any enquiries concerning this research project, please contact the relevant programme contact or email: science@foodstandards.gsi.gov.uk