The hygienic impact of categorisation of cattle by hide cleanliness in the abattoir

Abstract

In order to reduce hide-to-carcass contamination during slaughtering and dressing of cattle, the meat industry in Norway has developed national guidelines for Good Hygiene Practices based on hide cleanliness. Three categories of hide cleanliness have been described in Norway: Category 0 is clean, Category 1 is moderately dirty, and Category 2 is very dirty. For hides classified as either Category 1 or Category 2 payments to farmers are reduced. The aim of our study was to evaluate microbiological carcass contamination associated with hide cleanliness and the slaughtering and dressing process. A total of 324 swab samples were taken from abdomen and brisket areas (100 cm2 per sample) of 81 naturally contaminated beef carcasses at two commercial abattoirs. Samples were collected immediately after dehiding, at the start of the slaughter-line, and also at the end of the slaughter-line, just before chilling. Carcasses derived from dirty animals (Category 1 and Category 2 combined (n = 34)), were more contaminated just after dehiding than clean animals (Category 0, n = 47), as determined by aerobic plate counts (APC) (P < 0.001) and by Escherichia coli levels (P < 0.05). Also at the end of the slaughter-line, carcasses derived from dirty animals had higher APC levels than clean animals (P < 0.005). The carcasses had lower levels of APC and E. coli at the end of the slaughter-line than at the start for all categories (P < 0.05), and Category 1 carcasses had higher APC values than Category 0 carcasses at the start (P < 0.05) and at end of the slaughter-line (P = 0.05). The carcasses adjacent to carcasses classified as belonging to Categories 1 or 2, hanging just behind them on the conveyor-belt, were evaluated separately in order to investigate cross-contamination. At the end of the slaughter-line, carcasses that were adjacent to Category 2 carcasses had higher E. coli values than carcasses in all other categories.The national guidelines consider Category 2 carcasses as high-risk carcasses and they are processed separately, with heat treatment of the meat products. However, this study suggests that Category 2 carcasses seem to be of the same hygienic standard as those in other categories, perhaps because Category 2 carcasses are dehided and trimmed more carefully. However, since trimming of visual spot contamination seems sufficient for reducing microbial contamination to adequate levels, similar to those of cleaner animals, directing these carcasses into a separate meat process line, as demanded by the national guidelines, may be unnecessary.