Investigating feed and water curfews for the transport of livestock within Australia - A literature review

Summary

The reviewers agreed that food safety was a crucial factor that would drive the final on farm curfew conclusions and indeed total time off feed/water recommendations.

Food safety has both specific issues such selected pathogens like E. coli O157:H7 and Salmonella spp. and more general issues which are under pinned by carcase hygiene indicator organisms (i.e. E. coli biotype 1). Different markets have different requirements with respect to these issues.

Off-feed and water curfew is practiced on-farm to reduce soiling during transport and optimise hide/fleece cleanliness at slaughter. However in microbial terms it represents only one component of pre-slaughter management that influences microbial status of livestock and their subsequent influence on carcase contamination.

The food safety team concluded that to minimise transmission of pathogens and microbial contaminants during carcase dressing, emphasis should be on clean hides/pelts in livestock presented for slaughter. This will minimise direct contamination to the carcase from hide/pelt filth, and in doing so, reduce potential contamination from faeces containing high levels of hazards resulting from long periods off-feed.

While off-feed curfew reduces the potential for faecal contamination of hides/pelts, the additive effect of increasing time-off-feed (including on-farm curfew) on unwanted microbial growth within the intestines produces a countervailing effect. This clearly applies for both Salmonella and generic E. coli.

Off-feed curfews prior to transport of up to 24 hours are indicated to minimise soiling of the hide/pelt, which is associated with efficient dressing and lower carcase microbial counts. The total time off feed between the farm – slaughter interval is recommended not to exceed 48 hours due to its effect on unwanted microbial growth within the intestines.

The precise length of the curfew to maintain ‘clean’ stock is a complex equation determined by feed type (affecting soft versus hard faeces), coat/wool length and transport time. There is insufficient scientific data on the proportional contribution of these factors to resolve these issues. However Industry practice in commercial sheep supply chains (in Western Australia) suggest relatively short curfew periods are acceptable to allow carcase hygiene standards to be met (see overall conclusions and Table 2 below).

It is suggested that a “cleanliness” or outcomes-based standard should be supported by the implementation of a hide/pelt scoring system that could be related to the Cost analysis of dirty hides/pelts (dressing and microbiological) including feedback of scores and financial penalties to producers. A validated scoring system would then allow companies to undertake research with their clients to optimise the curfew periods rather than relying on conservative ‘blanket’ recommendations.

It cannot be assumed that pre-slaughter controls for generic E. coli and Salmonella will be effective for E coli O157/STEC from either grass or lot-fed production systems. The effect of pre-slaughter controls for sheep carcase hygiene is similarly unreliable. Therefore, greater focus should be on optimal dressing procedures to minimise hazards and the attainment of excellent microbiological status of carcases.

These should receive greater emphasis than pursuing complex pre-slaughter controls that are subject to considerable variation in microbial efficacy, and as such, are unsuitable as Critical Control Points within a HACCP system.