The effect of cattle cleanliness scores on bacterial contamination of carcasses

Torres, Gregorio (2004) The effect of cattle cleanliness scores on bacterial contamination of carcasses. MVM(R) thesis, University of Glasgow.

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Abstract

The control of inadvertent microbiological contamination of red meat carcasses has emerged in the last decade as the most important aspect of meat inspection and meat hygiene. The hide is recognised as the main sources of human pathogen contamination such as Campylobacter spp. or Mycobacterium avium subsp paratuberculosis. Introducing only clean cattle to the slaughter line partially minimises the potential for meat-borne zoonoses. Following the outbreaks of Escherichia coli O157 infection in Scotland in 1996, British abattoirs have imposed a scoring system called the Clean Livestock Policy (CLP), to assess the cleanliness of animals submitted for slaughter. The policy provides categories of a range of scores of dirtiness from 1 to 5. In this study, 93 over thirty month (OTM) cattle classified in all 5 different CLP categories, were assessed. Swab samples were taken from the flank of the carcass and using the wet and dry method as advised by the Meat Hygiene Service (MHS), the Total Viable Count (TVC), and Enterobacteriaceae count were determined. This study showed that the level of contamination on carcasses increased with an increase in the CLP score. Dirty carcasses with CLP score 3, 4 and 5, as defined by MHS, were found to carry up to 30,000 times more micro-organisms, defined by TVC, than clean carcasses with CLP sore 1 and 2. Different ante-mortem features of cattle were also studied and coat length, coat moisture, type of contamination, and site of contamination was shown to influence carcass contamination. The classification of dirty or clean cattle during the ante-mortem inspection in an abattoir lairage sometimes creates difficulties for the Official Veterinary Surgeon (OVS), as the MHS CLP score provides only descriptive details and pictures of cattle in the five different categories. In this study, three different decision trees were designed; two for each of the outcome variables, TVC and Enterobacteriaceae, and a third one for the CLP, with the goal to minimize subjective decisions. The association between carcass contamination and prevalence of potential zoonotic pathogens isolated from the cattle such as Campylobacter spp. and Mycobacterium avium subsp. paratuberculosis was studied. Different culture methods for isolation of Campylobacter spp. were employed. No colonies of Campylobacter spp. were found on direct swab samples from carcasses however Campylobacter spp. were isolated in faeces from 5 cattle using the combination Skirrow and Bluster medium. Of the 93 cattle sampled, eight cattle were found to carry Mycobacterium avium subsp. Paratuberculosis (MAP) by direct smear using the Ziehl Neelsen staining method, hi five cattle MAP were isolated from faeces, in one cattle from the lymph node and in two cattle MAP was isolated from both the lymph node and from faeces.

Item Type: Thesis (MVM(R))
Qualification Level: Masters
Additional Information: Adviser: Billy Steel
Keywords: Animal sciences, Food science
Date of Award: 2004
Depositing User: Enlighten Team
Unique ID: glathesis:2004-71902
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 17 May 2019 09:31
Last Modified: 17 May 2019 09:31
URI: http://theses.gla.ac.uk/id/eprint/71902

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