Project title:    Farm management practices to improve the visible and microbiological cleanliness of cattle hides at slaughter

Duration:         January 1st 2000 to 30th September 2003

Background and rationale

The number of reported cases of food-borne illness in the UK has risen dramatically over recent years and the high mortality rate associated with zoonotic agents such as verocytotoxic E. coli O157 has focussed the attention of the general public.  In addition to representing a major public health concern, outbreaks of food-borne illness can also result in significant economic loss.  Reducing the incidence of such events therefore is important and was one of the driving forces that led to creation of the Food Standards Agency .  An effective strategy for pathogen control during food production involves identifying each potential point of pathogen entry into the food chain, and implementing effective controls at these stages.

An enquiry into the outbreak of Escherichia coli O157 infection within the human population of central Scotland in 1996 highlighted the importance of adopting hygienic procedures in the red meat production chain.  The Pennington Report that was produced from the enquiry indicated that the original contamination source of the meat was likely to have been either faecal material or intestinal contents coming into contact with carcases at the point of slaughter.  The report further noted that the management of cattle prior to slaughter may have provided a means for ensuring animals presented for kill were in an acceptable condition from a microbiological viewpoint.

Objectives and Approach

The overall objective of the project was to investigate the interacting effects of diet and transport.  In addition, the influence of straw bedding and clipping on the visible and microbiological cleanliness of cattle presented at the abattoir were investigated as a number of individual objectives. The experimental aspects of the project were designed to investigate the effects of common farm management practices, including finishing ration, feed restriction prior to slaughter, level of bedding provision, clipping and duration of transport on both the visible and microbiological cleanliness of cattle.  The final objective was to complete a technology transfer programme which disseminated these research findings to the entire beef industry.

Results

In the first experimental objective, the role of the finishing ration was investigated and found to be the most significant factor affecting faecal shedding of potential zoonotic agents.  Feeding cattle on cereal-based rations for a two-month finishing period was associated with significantly higher levels of bacteria in the faeces, including E. coli O157, compared with cattle finished on a silage-based ration. The increased level of faecal shedding was also associated with increased levels of bacterial contamination on the hides of these animals, in particular at the brisket site. The effects of restricting feed intake prior to slaughter was also investigated, by switching cattle to a straw-only diet for 0, 1, 2 or 3 days. The effects of this feed restriction and its interaction with finishing ration, however, were more variable, with results being dependent upon the class of bacteria studied. The effect of journey time to the abattoir was also investigated in this experiment, although no major differences in visible or microbiological cleanliness were found between journey times of 2.5 and 6 hours.

In another experiment, the effectiveness of clipping and providing additional straw bedding on-farm for improving the cleanliness of cattle was investigated.  Both were found to improve the visible cleanliness of cattle, although the effects on the microbiological cleanliness were again more variable and dependant upon the class of bacteria studied.  Clipping was associated with a reduction in the total bacterial counts at the flank and shoulder sites, but there were no significant effects at the brisket site, possibly reflecting the fact that clipping the brisket is a very difficult operation to conduct. The improvement in microbiological cleanliness at the flank and shoulder sites was also relatively short-lived, indicating that clipping would need to be carried out almost immediately prior to slaughter, if it is to have any significant effect as an intervention measure to improve meat hygiene. Providing additional straw represents a much safer approach to cleaning dirty cattle, although straw prices may represent a significant financial obstacle to this in certain areas of the country. Clearly, an optimal strategy for hygienic meat is to prevent cattle becoming dirty in the first place.

The abattoir lairage is another potential source of contamination of cattle hides, and an experiment was conducted to investigate the effects of the duration of lairage and the provision of additional straw on the microbiological cleanliness of cattle. There was evidence that providing additional straw bedding may be beneficial, as the total aerobic count at the brisket site was reduced after overnight lairage.  However, effects at other sites and with other classes of bacteria were less clear-cut. The lairage remains an interesting area for further investigation, however, and may benefit from some novel approaches to the problem of keeping cattle clean.

The findings of this project were disseminated to the wider industry, through a technology transfer programme. This included a series of Information Days, Open Days and Press Articles. The technology transfer programme focused on disseminating Ten Key Messages which were:

1.         Livestock may carry zoonotic agents (bacteria harmful to humans but not livestock)

2.         The Clean Livestock Policy has improved cattle cleanliness

3.         Dirty cattle cost money

4.         Pre-slaughter diet needs consideration

5.         Providing adequate bedding improves cattle cleanliness

6.         Clipping can remove visible dirt

7.         Wet cattle are a significant hazard

8.         Transport factors can affect cattle cleanliness

9.         Mixing unfamiliar animals increases cross-contamination   

10.       Bacteria survive for extended periods in livestock environments

What it means and why it is important

These investigations have provided evidence that farm and lairage management practices have the potential to influence visible and microbiological cleanliness of cattle presented for slaughter.   The outputs of this study have provided farmers with clear advice on the best husbandry practices to adopt before sending their animals for slaughter.  Reducing the microbiological contamination of cattle hides prior to slaughter is a secondary control point in the meat production chain because it also reduces carcase contamination.  Cleaner carcasses are more likely to be free of zoonotic agents thereby making a contribution towards the Agency's target of further reducing foodborne illness by 2010.