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Farm management practices to improve the visible and microbiological cleanliness of cattle hides at slaughter
Project Code: M01013
ADAS High Mowthorpe
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 E. coli O157 infection in humans has brought the importance of ruminants as reservoirs of disease to the attention of the general public. Outbreaks of food-borne illness obviously present a major public health concern, but may also result in serious economic loss, both in the area affected and for the country at large. Reducing the incidence of such events, therefore, is of utmost importance. To date, the most effective strategy identified to achieve this involves determining each potential point of pathogen entry into the entire food chain, and then implementing effective controls to minimise contamination at each of these points.
The enquiry into the outbreak of Escherichia coli O157 infection in the human population of central Scotland in 1996 highlighted the importance of adopting hygienic procedures in the meat production chain. The Pennington Report indicated that contamination of the meat was likely to have occurred as a result of either faecal material or intestinal contents coming into contact with carcases at the abattoir. The report further noted that the management of cattle prior to slaughter may provide a means for ensuring animals presented for slaughter are in an acceptable condition in terms of hygiene.
Objectives and Approach
The overall objective of the project was to investigate the interacting effects of dietary and transport factors, and of straw bedding and clipping on the cleanliness of cattle presented at the abattoir. This was achieved by completing a number of individual objectives, including a literature review and on-farm experimental work. 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, to disseminate research findings from this and other FSA funded research to the entire beef industry.
In the first experimental objective, finishing ration was found to be the most significant factor affecting faecal shedding of potentially zoonotic bacteria. 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. This 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 Viable Count 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, the optimal strategies for meat hygiene, therefore, are those that 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 some suggestion that providing additional straw bedding may be beneficial, as the Total Viable Count at the brisket site was reduced after overnight lairage on this treatment, compared with counts from animals receiving normal bedding levels. However, effects at other sites and with other classes of bacteria were less perceptible. The lairage remains an interesting area for further investigation, however, and may benefit from some novel approaches to the problem of keeping cattle clean.
In addition to the food safety issues arising from the presentation of dirty cattle at abattoirs, dirty cattle pose significant problems to the leather industry, in terms of down-grading of the finished product. Damage to cattle hides associated with dirty cattle can be broadly classified into either dung damage, in which the grain of the leather becomes more open, due to long-term adherence of faecal material to the animals' coats, and clipper damage, whereby physical damage to the skin is inflicted when adherent material is removed using electric clippers. The final experimental objective investigated the effects of clipping and the visible cleanliness of cattle on the quality of the leather produced from their hides. The incidence of dung damage was relatively low at less than 5%, although all the down-graded hides did come from cattle that had been in a visibly dirty condition at the start of the experiment. No clipper damage was observed on any of the hides, although this is probably a reflection of the fact that animals were clipped in accordance with best practice guidelines.
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 agreed by a number of industry representatives, The messages are:
- Livestock may carry harmful bacteria
- The Clean Livestock Policy has improved cattle cleanliness
- Dirty cattle cost money
- Pre-slaughter diet needs consideration
- Providing adequate bedding improves cattle cleanliness
- Clipping can remove visible dirt
- Wet cattle are a significant hazard
- Transport factors can affect cattle cleanliness Mixing unfamiliar animals increases cross-contamination
- Bacteria survive well in livestock environments
What it means and why it is important
These investigations have provided evidence to show that farm and lairage management practices have the potential to significantly affect both the visible and microbiological cleanliness of cattle presented for slaughter. Reducing the microbiological contamination of the hides of cattle prior to slaughter represents a critical control point in the hygienic meat production chain, because it has the potential to reduce the level of carcase contamination. A reduction in the incidence and level of contamination of beef carcases is essential if the incidence of food-borne disease related to the consumption of contaminated beef products is to be achieved. Producing microbiologically cleaner cattle, therefore, has the potential to assist the Food Standards Agency to meet its Foodborne Disease Strategy Target of reducing the incidence of food-borne illness by 20% by the year 2006.
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