Trial of visual inspection of fattening pigs from non-controlled housing conditions

Last updated:
6 March 2013
This research aimed to establish if post mortem visual-only inspections, for pigs from non-controlled housing conditions ('outdoor pigs'), can be safely implemented.
Study duration: November 2011 to February 2013
Project code: FS145003
Contractor: Scottish Agricultural College

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A previous study funded by the Agency compared post mortem inspection (PMI) findings of ‘outdoor’ and ‘indoor’ fattening pigs, using a qualitative risk assessment approach (see project MC1002: Comparison of post-mortem inspection findings of outdoor and indoor fattening pigs: a qualitative risk assessment approach). The results suggested that moving to visual-only post mortem inspection for 'outdoor pigs' would not pose an increased risk to public health, animal health and welfare.

Traditional PMI includes palpation and incision which can potentially increase the risk of contamination, while visual-only PMI reduces handling of the carcass. This study focused on whether visual PMI of 'outdoor pigs' presents a significant risk above that accepted for 'indoor pigs' based on the current provisions in the regulations.

Research Approach

The pilot study examined 'outdoor pigs' which had been reared in non-controlled housing conditions at least since weaning. It aimed to establish the frequency and type of findings that could be expected when using visual-only inspection versus traditional inspection methods.

The effects on contamination levels, as a result of the handling of carcasses, were also investigated. The trial was designed so that all carcases were inspected or re-inspected according to current regulatory requirements, so they could be put on the market without risk.

Microbiological sampling for enterobacteriaceae, salmonella and yersinia were applied to identify differences in the risk of using traditional inspection methods for carcasses, compared to visual-only inspection.

The findings were used to identify any issues which may prevent the implementation of a risk based visual-only inspection system. Appropriate adaptations to overcome these problems, such as different dressing procedures or food chain information (FCI) requirements, were considered.

A qualitative risk assessment, on the impact of the implementation of visual-only inspection for outdoor pigs and its consequence on public health, animal health and welfare, was drawn up.


More than 11,000 carcases of fattening pigs from non-controlled housing conditions were inspected using both PMI methods (traditional and visual-only inspection). A baseline of type, frequency and distribution of conditions detected by both methods was established and then compared.

There were statistically significant differences in the frequencies found by the two inspection methods. For example, the frequencies were higher (with the traditional method of inspection) for renal pathology and pluck (heart, respiratory system and liver) pathology.

Five possible public health hazards were selected for further investigation:

  • endocarditis
  • granulomatous lesions
  • salmonella spp.
  • yersinia spp.
  • enterobacteriaceae

It was concluded that after visual-only inspection, the risk associated with endocarditis changed from negligible to very low and that the risk of microbial cross-infection might be reduced.
Salmonella spp. was not isolated from any of the samples and no statistical difference was found in the proportion of carcases contaminated with Yersinia spp. after the two inspection methods.
When carcases were examined where enterobacteriaceae were present, there was some evidence that the level of carcass contamination was lower after visual-only compared to traditional inspection. There was some evidence for a possible reduction in the cross contamination of carcases by changing the PMI method to a visual-only system where handling of carcases was minimised.

It was presumed that the major issues to introducing a visual-only inspection system for pigs from non-controlled housing conditions in the UK would be the same as those that are expected if the same were to be implemented for fattening pigs from controlled housing conditions.