Risk assessment of organoleptic postmortem inspection procedures for pigs

Adding value to food chain information: using data on pig welfare and antimicrobial use on-farm to predict meat inspection outcomes

BACKGROUND

Using Food Chain Information data to objectively identify high-risk animals entering abattoirs can represent an important step forward towards improving on-farm animal welfare. We aimed to develop and evaluate the performance of classification models, using Gradient Boosting Machine algorithms that utilise accurate longitudinal on-farm data on pig health and welfare to predict condemnations, pluck lesions and low cold carcass weight at slaughter.

RESULTS

The accuracy of the models was assessed using the area under the receiver operating characteristics (ROC) curve (AUC). The AUC for the prediction models for pneumonia, dorsocaudal pleurisy, cranial pleurisy, pericarditis, partial and total condemnations, and low cold carcass weight varied from 0.54 for pneumonia and 0.67 for low cold carcass weight. For dorsocaudal pleurisy, ear lesions assessed on pigs aged 12 weeks and antimicrobial treatments (AMT) were the most important prediction variables. Similarly, the most important variable for the prediction of cranial pleurisy was the number of AMT. In the case of pericarditis, ear lesions assessed both at week 12 and 14 were the most important variables and accounted for 33% of the Bernoulli loss reduction. For predicting partial and total condemnations, the presence of hernias on week 18 and lameness on week 12 accounted for 27% and 14% of the Bernoulli loss reduction, respectively. Finally, AMT (37%) and ear lesions assessed on week 12 (15%) were the most important variables for predicting pigs with low cold carcass weight.

CONCLUSIONS

The findings from our study show that on farm assessments of animal-based welfare outcomes and information on antimicrobial treatments have a modest predictive power in relation to the different meat inspection outcomes assessed. New research following the same group of pigs longitudinally from a larger number of farms supplying different slaughterhouses is required to confirm that on farm assessments can add value to Food Chain Information reports.

Critical Analysis of Pork QMRA Focusing on Slaughterhouses: Lessons from the Past and Future Trends

Foodborne microbial diseases have a significant impact on public health, leading to millions of human illnesses each year worldwide. Pork is one of the most consumed meat in Europe but may also be a major source of pathogens introduced all along the farm-to-fork chain. Several quantitative microbial risk assessment (QMRA) have been developed to assess human health risks associated with pork consumption and to evaluate the efficiency of different risk reduction strategies. The present critical analysis aims to review pork QMRA. An exhaustive search was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology. It resulted in identification of a collection of 2489 papers including 42 on QMRA, after screening. Among them, a total of 29 studies focused on Salmonella spp. with clear concern on impacts at the slaughterhouse, modeling the spreading of contaminations and growth at critical stages along with potential reductions. Along with strict compliance with good hygiene practices, several potential risk mitigation pathways were highlighted for each slaughterhouse step. The slaughterhouse has a key role to play to ensure food safety of pork-based products but consideration of the whole farm-to-fork chain is necessary to enable better control of bacteria. This review provides an analysis of pork meat QMRA, to facilitate their reuse, and identify gaps to guide future research activities.

Implementation of Visual-Only Swine Inspection in the European Union: Challenges, Opportunities, and Lessons Learned

ABSTRACT

Consumption of contaminated meat and poultry products is a major source of foodborne illness in the United States and globally. Meat inspection procedures, established more than 100 years ago to detect prevailing food safety issues of the time and largely harmonized around the world, do not effectively detect modern hazards and may inadvertently increase food safety risks by spreading contamination across carcasses. Visual-only inspection (VOI) is a significantly different, modernized meat inspection system that is data driven and minimizes physical manipulation of the carcass during inspection. It was developed based on scientific evidence and risk assessment and aims to better control current food safety hazards. In 2014, the European Union (EU) became the first supranational government in the world to require VOI for all swine herds slaughtered in member states that met certain epidemiologic and animal rearing conditions. Here, we review the implementation of this new inspection system with the goal of informing similar modernization efforts in other countries and for other commodities beyond pork. This article reports the results of a literature review and interviews conducted with nine experts in 2018 on the implementation of the EU's 2014 VOI regulation. Challenges, opportunities, and lessons learned about the implementation of the regulation are described for audiences interested in adapting inspection procedures to prevent and detect modern food safety hazards. Overall, implementation of VOI varies within and across member states, and among slaughterhouses of different sizes. This variation is due to disease risk patterns, supply chain conditions, and trade barriers. Before transitioning to a similar risk-based meat inspection system, other countries should consider the following: science-based research agendas to identify what food chain information best predicts herd health and foodborne hazards, regulatory system design that accurately reflects local hazards, and development of targeted VOI educational materials.

HIGHLIGHTS

Modeling of Salmonella Contamination in the Pig Slaughterhouse

In this article we present a model for Salmonella contamination of pig carcasses in the slaughterhouse. This model forms part of a larger QMRA (quantitative microbial risk assessment) on Salmonella in slaughter and breeder pigs, which uses a generic model framework that can be parameterized for European member states, to describe the entire chain from farm-to-consumption and the resultant human illness. We focus on model construction, giving mathematical formulae to describe Salmonella concentrations on individual pigs and slaughter equipment at different stages of the slaughter process. Variability among individual pigs and over slaughterhouses is incorporated using statistical distributions, and simulated by Monte Carlo iteration. We present the results over the various slaughter stages and show that such a framework is especially suitable to investigate the effect of various interventions. In this article we present the results of the slaughterhouse module for two case study member states. The model outcome represents an increase in average prevalence of Salmonella contamination and Salmonella numbers at dehairing and a decrease of Salmonella numbers at scalding. These results show good agreement when compared to several other QMRAs and microbiological studies.

Effects of slaughtering operations on carcass contamination in an Irish pork production plant

Background

Microbiological standards within pork slaughter processing plants in the European Union are currently governed by Commission Regulation (EC) 2073/2005, which describes detailed performance criteria at specific stages of the procedure (following carcass dressing and before chilling) for total viable counts (TVC), Enterobacteriaceae (EB) and Salmonella spp. In this study, 95 carcasses from an Irish pork slaughter plant were sampled by swabbing 100 cm² of surface at three sites (belly, ham, jowl) to examine the effects of eight processing stages (stunning, bleeding, scalding, singeing, polishing, evisceration, final inspection and chilling) on contamination levels.

Results

TVC ranged from approximately 1.7–6.3 log cfu cm² during sampling. There were significant reductions in TVC for all sites after scalding and singeing (p < 0.05), whilst there was a significant increase in counts after polishing and evisceration (p < 0.05) compared with preceding stages. EB counts indicated hygienic weak points in the examined slaughter plant leading to faecal (cross)-contamination, with elevated counts after stunning, bleeding and evisceration (p < 0.05), compared with final counts after chilling.

Conclusions

Although the bacterial numbers reported in this study may reflect specific plant practices and temporal influences, results show that contamination can be introduced at various steps in the process and highlight the importance of monitoring locations other than those required by legislation within the process. Monitoring can be used to establish baseline levels for high-risk stages specific to each plant and to assess the effectiveness of additional interventions.

Mycobacterium avium subsp. avium in lymph nodes and diaphragms of pigs from one infected herd in the Czech Republic

This study was performed on 40 finished pigs from one herd naturally infected with Mycobacterium avium subsp. avium. The aim was to investigate the presence and amount of M. a. avium in samples of lymph nodes and diaphragm tissues collected during routine postmortem inspection using the triplex quantitative real time PCR (qPCR) method. We collected, in total, 107 samples: various lymph nodes affected by gross tuberculosis (TB)-like lesions from 17 pig carcasses, as well as samples of head and mesenteric lymph nodes from 23 carcasses without TB-like lesions. Samples of diaphragm tissues were collected from all carcasses. M. a. avium was detected in one or more tissue samples collected from half of the slaughtered pigs tested. Samples of diaphragm tissues of three pigs with detected TB-like lesions contained M. a. avium (10(2) to 10(3) cells per g of sample); the organism was not detected in diaphragm tissues from pigs without TB-like lesions. The qPCR method may be useful for quantification of M. a. avium in pigs for the purposes of foodborne risk assessment.

Assessment of current disease surveillance activities for pigs post-farmgate in New South Wales

OBJECTIVES

Evaluate current disease surveillance activities at saleyards and abattoirs in New South Wales (NSW) in order to establish the prevalence of clinical anomalies in pigs at different sites and to compare the sensitivity of detecting anomalies inside versus outside of pens.

PROCEDURE

Routine inspections of pigs by staff and government inspectors were observed at two saleyards and two abattoirs in NSW during three visits over a 2-month period (January 2008-March 2008). All pigs presented for sale or slaughter were examined for 19 clinical anomalies from either the side of the pen or while animals were moving outside the pen, with data being combined to give an assumed 'gold standard'. We compared the prevalence of anomalies among animals at the four sites using logistic regression, as well as the sensitivity of detection of the two inspection methods.

RESULTS

Frequency and methodology of routine inspection varied among sites. Of the 7747 pigs inspected, 822 (10.6%) showed at least one clinical anomaly. There was moderate agreement between detecting anomalies in penned pigs versus while being moved. Pigs at one abattoir exhibited significantly fewer anomalies than pigs at the other sites.

CONCLUSION

The prevalence of anomalies among pigs at saleyards and abattoirs in NSW was relatively high ( approximately 10%). Weaknesses in current disease surveillance activities for pigs post-farmgate have been identified. Increased regulation, surveillance training and modification of standard operational procedures for inspection have the potential to improve the current system.

Feasibility of screening broiler chicken flocks for risk markers as an aid for meat inspection

The feasibility of using risk markers to screen broiler chicken flocks and anticipate their risk of condemnation at meat inspection was examined in 404 randomly selected flocks in 15 French slaughterhouses in 2005. Condemnation rate and information about rearing conditions, health history, catching and loading, transport and slaughtering were collected. The Poisson regression model of the condemnation rate consisted of six simple and biologically relevant predictors: production type, frequency of farmer's visits during the starting period, health disorders during rearing, on-farm mortality, mortality during transport, and slaughter-line speed. Although accurate prediction of the condemnation rate for a given flock was not feasible, flocks with low or high risk of condemnation could be distinguished. These findings could be useful at various stages of chicken production, to monitor and improve farm husbandry practices, minimize the impact of transport conditions, and optimize meat inspection procedures.

Swine health impact on carcass contamination and human foodborne risk

OBJECTIVE

This study measured the relationship between lesions suggestive of subclinical pig illness at harvest to carcass contamination and human foodborne risk.

METHODS

Over the course of eight visits (December 2005 to January 2006), we swabbed 280 randomly selected carcasses, during normal slaughter operations, at three points in the slaughter line: skin pre-scald; the bung or pelvic cavity following removal of the distal colon and rectum; and pleural cavity, immediately before the final carcass rinse. Each swab sponge was used on five carcasses in bung and pleural cavity sampling. Swab sponges were cultured quantitatively for Campylobacter spp., Enterococcus spp., and Enterobacteriaceae spp., and qualitatively for Salmonella spp. Data on health indicators were collected for all pigs in the study (2,625 pigs) by experienced plant quality assurance personnel.

RESULTS

Campylobacter spp. were recovered from the pleural cavity in 58.9% (33/56) of pools (five carcasses/pool), and in 44.6% (25/56) of pools from the bung cavity. Enterococcus spp. were recovered from 66.1% (37/56) and 35.7% (20/56) of pleural and bung pools, respectively. The most common lesion identified was the peel-out (pleuritis or adhesions), with a total of 7.1% (186/2,625 total head). Linear regression showed that for every percentage point increase in peel-outs, Enterococcus spp. contamination increased by 4.4% and Campylobacter spp. increased by 5.1% (p<0.05).

CONCLUSIONS

This study showed a correlation between animal health and human health risk, as measured by carcass contamination. Therefore, animal management decisions on-farm, such as housing, antibiotic use, environment, and level of veterinary care, may directly impact public health.

Assessment of producer conducted antemortem inspection of market pigs in Australia

OBJECTIVE

A field trial was conducted to evaluate the effectiveness of on-farm antemortem inspection performed by Australian pig producers in terms of proficiency in detecting unhealthy animals (suspects), the impact on food safety and animal welfare outcomes.

ANIMALS

A total of 64 trial groups of market pigs (n= 10,703) were dispatched from 20 herds to three abattoirs in three states.

PROCEDURE

All producers and abattoir antemortem inspectors were trained in antemortem inspection prior to the trial using a standardised set of antemortem criteria. Study 1 consisted of three comparisons: on-farm versus abattoir antemortem inspections on the same pigs, transport effects in suspect and normal pigs, and meat rejection and carcase disposition in suspect and normal pigs. Study 2 compared Salmonella spp status of suspect and normal pigs. Studies 3 and 4 were conducted to assist the interpretation of the results of on-farm versus abattoir inspection. Antemortem inspection results of three producers and one abattoir antemortem inspector were compared with those of a reference inspector (Gold Standard).

RESULTS

Of the pigs examined, 2.12% (95% CI: 1.84%, 2.42%) were classified as suspect at on-farm antemortem inspection compared to only 0.14% at abattoir antemortem inspection. Forty one percent of pigs classified as suspect on-farm had locomotor problems (arthritis, lameness and foot abscess). Compared to normal pigs, suspect pigs had a relative risk of 67.7 (P < 0.0001) of suffering transport injuries. Meat rejection amounted to the equivalent of 9.68% of suspect carcases, compared to the equivalent of 0.35% of normal carcases. The isolation of Salmonella species from caecal content from 20.9% of 67 suspect pigs and 18.8% of 133 control pigs (two matched healthy pigs from the same batch for each suspect pig) were not significantly different. When compared with the reference inspector on-farm, three producers classified abnormalities in 2,495 pigs with high specificity (0.98), acceptable sensitivity (0.82) and kappa (0.57).

CONCLUSIONS

With training, producer sensitivity in antemortem inspection may be high and more proficient than abattoir antemortem inspection. Use of producer inspections may have benefits for animal welfare and chain efficiency, but not food safety.

Assessment of producer conducted antemortem inspection of market pigs in Australia

OBJECTIVE

A field trial was conducted to evaluate the effectiveness of on-farm antemortem inspection performed by Australian pig producers in terms of proficiency in detecting unhealthy animals (suspects), the impact on food safety and animal welfare outcomes.

ANIMALS

A total of 64 trial groups of market pigs (n = 10,703) were dispatched from 20 herds to three abattoirs in three states.

PROCEDURE

All producers and abattoir antemortem inspectors were trained in antemortem inspection prior to the trial, using a standardised set of antemortem criteria. Study 1 consisted of three comparisons: on-farm versus abattoir antemortem inspections on the same pigs, transport effects in suspect and normal pigs, and meat rejection and carcase disposition in suspect and normal pigs. Study 2 compared Salmonella spp. status of suspect and normal pigs. Studies 3 and 4 were conducted to assist the interpretation of the results of on-farm versus abattoir inspection. Antemortem inspection results of three producers and one abattoir antemortem inspector were compared with those of a reference inspector (Gold Standard).

RESULTS

Of the pigs examined, 2.12% (95% CI: [1.84%, 2.42%]) were classified as suspect at on-farm antemortem inspection compared to only 0.14% at abattoir antemortem inspection. Forty one percent of pigs classified as suspect on-farm had locomotor problems (arthritis, lameness and foot abscess). Compared to normal pigs, suspect pigs had a relative risk of 67.7 (P < 0.0001) of suffering transport injuries. Meat rejection amounted to the equivalent of 9.68% of suspect carcases, compared to the equivalent of 0.35% of normal carcases. The isolation of Salmonella species from caecal content from 20.9% of 67 suspect pigs and 18.8% of 133 control pigs (two matched healthy pigs from the same batch for each suspect pig) were not significantly different. When compared with the reference inspector on-farm, three producers classified abnormalities in 2495 pigs with high specificity (0.98), acceptable sensitivity (0.82) and kappa (0.57).

CONCLUSIONS

With training, producer sensitivity in antemortem inspection may be high and more proficient than abattoir antemortem inspection. Use of producer inspections may have benefits for animal welfare and chain efficiency, but not food safety.

Risk-based evaluation of postmortem inspection procedures for pigs in Australia

The results of traditional (incision) and risk-based (visual) postmortem inspection procedures were compared on groups of approximately 30,000 pigs. The performance characteristics used as a basis for comparison included the non-detection rates of grossly detectable abnormalities, the microbiological contamination rates of carcases and boned product, the association of reactive lymph nodes with carcase condemnation and the achievement of 'finished product standards' for 'wholesomeness'. It was estimated that 6 per cent of all cases of abscessation and 28 per cent of all cases of arthritis were undetected by the traditional method, and the comparable figures for the risk-based procedure were 19 per cent and 39 per cent. However, when the rates of contamination of undetected abnormalities with foodborne hazards and other carcase contamination parameters were taken into account, it was concluded that both inspection systems were likely to result in a very similar level of consumer protection. Any increase in potential exposure to foodborne hazards in the abnormalities undetected by risk-based inspection would be insignificant in comparison with the potential exposure to foodborne hazards resulting from contaminated 'normal' lymph nodes and carcase surfaces. There were no statistically significant differences between the two procedures in the contamination rates of pre-chill carcases or boned retail products with Salmonella and Yersinia species.

Food safety on the slaughterline: inspection of pig heads

This paper summarises information on the current inspection procedures for pig heads on the slaughterline and their impact on food safety, and considers the implications for food safety of certain lesions. It is argued that although a modified slaughter and inspection technique would decrease the contamination of the carcase with pathogenic microorganisms, leaving lesions in the head undiscovered would be of little or no importance either for human health or for the overall supervision of animal health.

Assessment of organoleptic postmortem inspection techniques for bovine offal

OBJECTIVE

To evaluate organoleptic postmortem inspection techniques for bovine livers and kidneys.

STUDY DESIGN

At Australian export abattoirs, bovine liver and kidneys are assessed and graded by qualified meat inspectors during normal operations. Over a 12-month period at a large abattoir in eastern Australia during 1997 and 1998, a sample of these organs was reassessed independently using a range of pathological and microbiological methods. Agreement between routine inspection and independent assessment was evaluated using methods of inter-rater agreement.

RESULTS

A total of 944 livers and 1374 kidneys were included in the study. All of these organs had been classified during routine inspection. The authors examined 363 livers and 329 kidneys both grossly and histologically, including 36 livers and 14 kidneys that were also subjected to microbiological examination. All other organs were only examined grossly. There was only a moderate level of agreement between the routine and independent assessment methods. For livers, the percentage agreement was 80.2%, McNemar's test of symmetry 55.2 (3 degrees of freedom, P < 0.001) and kappa 0.63. For kidneys, the percentage agreement was 67.8%, McNemar's test of symmetry 9.9 (1 df, P = 0.002) and kappa 0.35.

CONCLUSIONS

The results reinforce concerns from a number of authors about organoleptic postmortem inspection. Risk assessment methodologies offer the opportunity to modify inspection techniques in a manner that is most relevant to current public health concerns.