Summary
Livestock may be colonised by potentially pathogenic microorganisms prior to slaughter, and if care is not taken during the procedures of handling, transporting, slaughtering and dressing livestock, the edible portions of the meat carcass surface can become contaminated with organisms capable of causing foodborne illness in humans. Of particular concern to consumers, and thus to producers and processors, are Salmonella spp. and enterohaemorrhagic E.coli (EHEC). Major outbreaks of foodborne illnesses in recent years have lead to the implementation of Hazard Analysis Critical Control Point (HACCP) based quality systems to control the microbial contamination of carcasses. It is important to consider all aspects of carcass hygiene when developing contamination control strategies. This will include pre-slaughter treatment of livestock, which has been shown to influence the microbial contamination of meat surfaces.
It is largely accepted as logical that livestock with high faecal contamination, mud, or dirt pose a significant threat of possible bacterial contamination on the resultant carcass. It is presumed that this threat can be minimised by presenting clean cattle to slaughter, and some work supports this contention. However, other studies indicate that the level of cleanliness of the presented animal bears little relationship to the microbial contamination of the subsequent carcass. This may be due to the effectiveness of processing interventions available to the processor. Difficulties arise when comparing the results of different studies, related to differing sampling techniques and methodologies, and different microbiological analysis of samples. Studies in which accepted standard testing and sampling practices have been used, in accordance with the Australian regulatory authorities and USDA MegaRegs, may be expected to provide more relevant information for Australian processors than other studies. It is suggested that these discrepancies in studies which attempt to establish direct correlation between presented cattle and the microbial load on the final product are due to the many confounding contributions within the production line itself, including different line speeds and the general hygiene of the processing environment.
Most studies completed within operating abattoirs may exclude excessively dirty cattle from the chain, or slow the chain to take extra care or extra trimming of the carcass in order to comply with current industry regulation. Processing interventions that have been shown to reduce microbial contamination on carcasses include knife trimming, carcass washing using hot water, UV irradiation, steam vacuuming, steam pasteurisation, and use of chemical washes (including organic acids, chlorine, and trisodium phosphate). The effect of these treatments on the meat and hide quality of the product must be considered in any implementation strategy. Early HACCP plans for beef processing would often identify multiple critical control points in the process. Codex Alimentarius has revised the definition of a critical control point (CCP) as a stage of processing in which control is necessary to prevent or eliminate a food safety hazard (to an acceptable level). The generally accepted CCP in the beef slaughter plant are bactericidal washes or other intervention strategies, and chilling.
This does not mean that other stages of processing at which contamination may occur should not be controlled, but rather that this control is part of Good Manufacturing Process or Standard Operating Procedures. This change in approach to CCP designation will impact on HACCP planning, as it is possible that presentation of clean livestock pre-slaughter will not be designated as a critical control point in current systems. The HACCP system is designed to provide an outcome of safe food, and the evidence suggests that this outcome can be attained despite the presentation state of cattle. However, the appeal of deleting this control point from HACCP plans may not marry well with industry obligations to meet regulatory requirements, nor maximise profitability to the producer by returns on hides.
