Risk assessment of organoleptic postmortem inspection procedures for pigs

A systematic quantification of foodborne hazards in abnormal and normal tissues of pig carcases was undertaken to provide a risk-based assessment of the effectiveness of traditional organoleptic meat inspection. A total of 36,059 pigs, representing all major pig-producing areas and systems in Australia, were inspected on a seasonal basis at three abattoirs over 12 months. The prevalence of grossly detectable abnormalities of possible food-borne disease significance was recorded. A subset of the grossly detectable abnormalities, together with tissues classified by inspection as normal (controls) were submitted for the detection of a broad range of food-borne hazards. The potential exposure of consumers to hazards in fresh pork was characterised as the number of carcases per 10,000 containing hazards in selected tissues. The results indicated that the level of exposure of consumers to microbiological hazards in fresh pork is unlikely to be reduced significantly by the detection and removal of gross abnormalities in the tissues examined. On the basis of carcase throughput, the rate of contamination of normal lymph nodes was commonly 100 times higher, and no hazards were isolated from two types of grossly abnormal nodes. While further processing, cooking and handling may alter the exposure characterisation, the study nevertheless identifies the proportional contribution of abnormal and normal tissues to risks to consumers and clearly identifies the need for consideration of 'visual only' inspection in the re-evaluation of traditional inspection procedures.     

Evaluation of Abattoir Inspection for the Diagnosis of Mycobacterium bovis Infection in Cattle at Addis Ababa Abattoir

Detailed postmortem examinations were conducted to evaluate the efficiency of meat inspection procedures and to determine the distribution of lesions in Mycobacterium bovis-infected cattle. The study involved routine inspection at slaughter, collection of tissues for detailed examination in the laboratory, and bacteriological examination to identify M. bovis. Additionally, a 10-year (1992--2001) meat inspection record was analysed to determine tuberculosis trends in the past decade. chi2-Test and simple regression were used to analyse the data. Out of 1350 cattle examined, 1.5% were found with tuberculous lesions. Routine abattoir inspection detected only 55% of cattle with confirmed lesions. Fifty-four per cent of tuberculous lesions were found in the lungs and thoracic lymph nodes, 23% in the lymph nodes of the head, and the remaining 23% in the mesenteric and other lymph nodes of the carcase. M. bovis was additionally isolated from an animal that had no gross lesions of tuberculosis. On average, the annual rate of whole-carcase condemnation due to generalized tuberculosis was 0.024% and it has increased annually by 0.34% over the past decade. The rate of whole-carcase condemnation indicates a high degree of TB transmission and requires immediate attention from both the economic and public health points of view. The lower sensitivity of routine abattoir inspection confirms the importance of improving necropsy procedures.     

Controlling microbial contamination on beef and lamb meat during processing

SUMMARY The microbiological quality of carcases, meat and environmental surfaces was evaluated in commercial boning rooms processing beef and lamb. There was considerable variation in the level of microbial contamination on both carcases and meat, with counts ranging from less than 20 to 10⁸/cm² on carcases and to 2 times 10⁷/cm² on meat. The level of microbial contamination on meat was influenced by the level of carcase contamination at boning and by the boning process itself. Carcase contamination was the major determinant of microbiological quality, as more than 70% of carcases had microbial counts greater than 10³/cm². Cutting boards were a major source for microbial dissemination during boning, particularly when carcase counts were less than 10³/cm². If carcases were heavily contaminated, the contamination of processing surfaces was irrelevant in determining microbial loads on meat. Where carcase contamination was at low to moderate levels, the contribution of the boning process to the contamination on meat assumed increased significance. Under these conditions, improved sanitation of cutting surfaces in the boning room resulted in a significant reduction in microbial contamination on the surface of meat. These results can form the basis for ensuring that improvements made in carcase management before boning, to improve microbiological quality, will be preserved through attention to cutting board hygiene during boning.     

Observations on Cysticercus bovis in slaughter cattle in the Matabeleland province of Zimbabwe

Cysticercus bovis was detected at meat inspection in 2.16 per cent of 102,087 carcases of cattle from Matabeleland Province, slaughtered in Bulawayo during a period of 11 months. Lightly infested (detained) carcases accounted for 95 per cent of those with cysticercosis. The head was the only site affected in 58.4 per cent of the detained carcases, the shoulder in 20.1 per cent and the heart in 7.9 per cent. In more heavily infested (condemned) carcases 81.1 per cent had at least three sites affected. The incidence of cysts was highest in older male animals but in younger animals it was highest in cows. In the detained carcases an average of 1.5 cysts were found, of which 76 per cent were live and 24 per cent dead. Condemned carcases had more than 58 cysts on average, of which 98 per cent were live and 2 per cent dead. Live cysts were more common in older cattle and dead cysts were more common in younger animals. The incidence of C bovis in carcases of cattle originating from communal areas was 3.2 per cent compared with 1.6 per cent in those originating from commercial farms.     

Prevalence of 'head shooting' and the characteristics of the wounds in culled wild Scottish red deer

The carcases of 230 wild, culled red deer (Cervus elaphus) were examined for the presence of bullet wounds and permanent wound tracts to determine the prevalence and significance of wounds involving the head, legs or carcase trunk. Head wounds were found in 17 (7.4 per cent) of the carcases and were classified into two groups: nine in which the marksman was considered to have specifically targeted the head, and eight carcases in which the head wound was considered to have resulted from a ;coup de grace' shot to dispatch a previously wounded animal. The analysis of the wound data from the carcase trunks, in combination with data collected in a previous study, indicates that the initial wound tracts in all the deer appeared to have lower mean terminal probabilities than subsequent wound tracts, and that this effect is exacerbated during the rut.     

Revised post-mortem inspection procedures for cattle and pigs slaughtered Australian abattoirs

Revised procedures for the post-mortem inspection of cattle and pigs at Australian abattoirs were developed as minimum national requirements. Comparative trials of current and revised procedures were conducted at 3 and 4 Australian abattoirs for pigs and cattle respectively. Residual pathological changes after inspection and removal of lesions from heads, carcases or viscera were recorded by an evaluation team with the data used to determine relative effectiveness. For cattle, there was no significant difference between current and revised procedures. Although it had been proposed to eliminate routine incision of cervical lymph nodes for pigs, it was found necessary to retain this procedure. The data also revealed a significant variation in detection of pathology between abattoirs for both species. Parasitic conditions accounted for the greatest proportion of undetected lesions in both species for both current and revised procedures. These comprised mainly fascioliasis in cattle and ascariasis in pigs. The former was associated with the study being conducted in eastern Australia. Chronic interstitial nephritis was also a common undetected lesion, reinforcing the need for intensified inspection of kidneys. However, such residual pathology was considered to be of only limited significance to human health. The revised procedures and findings are discussed in the context of animal and human health and of the importance of the meat industry to Australian exports. Some attention has been given to specific conditions likely to be affected by the proposals including tuberculosis, bovine cysticercosis, fascioliasis, porcine arthritis and salmonellosis. The role of meat inspection in monitoring for specific diseases is discussed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Infection of pigs with transmissible gastroenteritis virus from contaminated carcases

Sixteen 6-month-old pigs were exposed to transmissible gastroenteritis (TGE) virus by placing them in close contact with piglets infected at 1 week of age. Fourteen of the older pigs were slaughtered between 1 and 5 d after exposure to infection and their carcases dressed in simulated abattoir conditions. Samples of muscle, bone marrow and carcase lymph nodes were stored at -25 degrees C for at least 30 d and then homogenised and fed to groups of 1-week-old and 3-week-old pigs. Four of 12 one-week-old pigs died and TGE virus was isolated from intestinal contents of one of these. All pigs of both age groups developed neutralising antibody to TGE virus over the ensuing 4 w. The results indicate that carcases from pigs infected with TGE virus can represent a source of infection for susceptible pigs given access to them.     

Genetic improvement in beef cattle using a progeny testing system based on carcase merit

A progeny testing system to measure beef carcase merit, the Abtech Test, has been developed. Nine carcase characteristics are measured objectively at a slaughter age of 300 days on the carcases of 12 steer progeny per sire. Five carcase characteristics were used to quantify the carcase, namely, carcase composition as submitted, carcase composition (adjusted to 20% total carcase fat), estimated lean meat yield (adjusted to 20% total carcase fat), muscle-bone ratio (adjusted to a common muscle plus bone weight), and eye muscle volume index (adjusted for total carcase muscle weight). Four carcase measurements used to describe quality were evaluated: eye muscle area at the 10th rib (adjusted for total carcase muscle weight), marbling of the eye muscle at the 10th rib (chemically determined and adjusted to 20% total carcase fat), muscle texture at the 10th rib (mean muscle bundle diameter) and fat colour (determined on intermuscular fat at the 10th rib under standard conditions).
It is proposed that this testing system could be used for the genetic improvement of beef carcases.     

Microbial cross-contamination by airborne dispersion and contagion during defeathering of poultry

1. A readily identifiable strain of Escherichia coli K12 was used as a 'marker' organism to determine the sources, routes and patterns of microbial cross-contamination during mechanical defeathering of broiler chicken carcases. 2. Inoculation of scald water with the marker organism led to a relatively even pattern of carcase contamination during subsequent defeathering. Microbial cross-contamination was greater by this route of inoculation than by either surface inoculation of a 'seeder' carcase or oral inoculation of a live bird one day before slaughter. 3. Dispersal of the marker organism was strongly influenced by the mechanical action of the defeathering machines. Forward transmission of the marker occurred by aerosol or large airborne droplets and particulates such as feathers. Moving carcases through the defeathering machines when these were non-operational clearly reduced backward transmission of the marker. 4. Although microbial dispersal was unaffected by increasing the spacing between individual carcases or installing a water curtain at the entry and exit of the defeathering machines, shielding of carcases with aluminium baffles reduced counts of the marker organism from contaminated carcases by > 90%. 5. The results imply that microbial cross-contamination of broiler chicken carcases during defeathering occurs mainly via the airborne route, which could be contained by physical means.     

Risk factors associated with Salmonella enterica subsp. enterica contamination of chicken carcases in Senegal

This study was to identify the risk factors for Salmonella spp. contamination of Senegalese chicken carcases during slaughtering. One hundred and twenty traditional slaughterhouses were studied from January 2000 to December 2002 in and around Dakar. A questionnaire was answered by the slaughterers, and samples of breast skin were taken to assess the Salmonella status of chicken carcases. Results showed that 43.3% of the batches were contaminated with Salmonella, indicating Salmonella Hadar and Salmonella Brancaster as the two main serovars. Salmonella contamination of the carcases after slaughtering was related to contamination of the live birds. Feed withdrawal before slaughtering and thorough cleaning and disinfection procedures decreased the risk of contamination. One individual worker for each slaughtering stage was also associated with a decreasing risk of contamination. Using scalding water for plucking the chicken carcases increased contamination risk. These results will help slaughters to produce safer products for local consumers.     

Meat inspection in the Australian red-meat industries: past, present and future

Postmortem inspection of carcases and offal has been a cornerstone of consumer protection in the red-meat industry for over a century. In 2011, there began strong moves to reform the traditional process of meat inspection applied to cattle, sheep and goats in Australia. A major motivation was the widespread acceptance that organoleptic inspection does little to control the most important hazards in meat products - microbial pathogens derived from gut flora. The watershed reforms in international trade provided another incentive by encouraging the application of a risk-based approach to food safety, which allows for the discontinuation of processes that do not enhance public health outcomes. As well, there was a strong imperative to ensure that resources allocated to quality assurance delivered maximum economic benefit for both consumers and processors. This review discusses how the role of meat inspection is likely to evolve into the future under the influence of these forces. It summarises how the current system was derived through repeated modification over time, mainly to satisfy the requirements of trading partners. Major developments are summarised, focusing especially on how the inclusion of particular organoleptic techniques was initially justified and the relevance of these to modern meat production. Overall, analysis of past and present practices suggests that in the future both public health and efficiency will be better served by strategically integrating the most effective elements of traditional organoleptic inspection with information from the preslaughter period and the use of modern technology for rapid and accurate detection of hazards.     

Detection of high serological prevalence and comparison of different tests for Salmonella in pigs in Northern Ireland

Thirty-one farrow-to-finish pig units with a Zoonoses National Control Programme (ZNCP) for Salmonella above the UK target of 10 per cent during the previous 12 months were selected for the study. Pooled faecal samples were collected from different groups of pigs. Furthermore, mice, rat and bird faeces and carcases were collected, if found on the unit. In total, 937 samples were collected on-farm and analysed for Salmonella. The four carcases selected monthly per producer by the slaughterhouse for the British Pig Executive ZNCP Salmonella Programme were tested for antibodies to groups B and C with a mix-ELISA test. The same four carcases were swabbed externally and internally, mesenteric lymph nodes (MLNs) were collected and colonic contents were swabbed. A wide variety of Salmonella serovars was isolated from the samples. Most of the isolates were detected in the rearing herd (on-farm) and in the MLNs (slaughterhouse). There was no correlation between ELISA results from the meat juice and bacteriological isolations using Spearman correlation analyses. Furthermore, no significant association was found between positive results of ELISA and positive results from the bacteriological samples taken.     

Dispersal of micro-organisms in commercial defeathering systems

1. The extent of cross contamination between carcases and the dispersal of micro-organisms to the environs during defeathering was measured in a commercial processing plant. 2. Defeathering reduced the numbers of a marker organism, a nalidixic acid-resistant strain of Escherichia coli K12, on inoculated carcases but dispersed the organism on to preceding and following carcases. 3. The pattern of microbial dispersal during defeathering was similar for naturally occurring bacteria on the carcase, for example, total aerobic counts and counts of presumptive coliforms, suggesting that the marker organism mimics the natural situation realistically. 4. The majority of feathers, together with micro-organisms, were removed during the first 10 s of the defeathering process, which was completed in 45 s, indicating that control measures to minimise cross contamination would be most effective if applied in the early stages of the process. 5. The method of defeathering used by the machine influenced the pattern of microbial dispersal and the extent of cross contamination to other carcases on the same processing line.     

Influence of the design of facilities at auction markets and animal handling procedures on bruising in cattle

The movements of cattle at 12 livestock auction markets were observed to determine the possible causes of trauma leading to carcase bruising. Design faults included right-angled bends in races, dead ends, flooring with insufficient slope or grip, and steps. Sliding gates were often misused for goading cattle. Projecting fittings and square-edged corners were potentially injurious; conversely, rounded posts and curved races assisted the flow of cattle with minimal impacts. At all the markets, some cattle were hit directly and poked with wooden sticks, and the variations in their use could partially explain the differences between the markets in the prevalence of carcase bruising. Most harder hits were directed at less valuable parts of the body, such as the spine, hips and shoulders, and a survey of bruising at the abattoir showed that these were the areas with most bruising. In this survey of 48,926 carcases, the overall level of commercially significant bruising of 4.1 per cent was lower than the 6.5 per cent found in a previous survey. Carcases of cattle from markets had a greater incidence and severity of bruising (P<0.001) than those arriving directly from farms or dealers. Carcase bruising in young bulls was less (P<0.001) than in heifers and steers.     

Survey of permanent wound tracts in the carcases of culled wild red deer in Scotland

The number and sites of permanent wound tracts in the carcases of 943 wild culled red deer (Cervus elaphus) were recorded. During the peak period of the red deer rut there was a significant increase in the number of these tracts in the carcases, which was associated with a decrease from 89 per cent to 71 per cent in the probability of the first permanent wound tract also being the last (the terminal probability). There were significantly more permanent wound tracts in the carcases of one group (predominantly males) than in a second group (predominantly females and calves). In carcases with a single tract in the trunk, in which the heart and lungs were also examined, 80 per cent had tracts involving the heart and/or lungs, the recommended thoracic target organs. Tracts involving vital structures in the neck were also common, with 15.3 per cent of the carcases with a single permanent tract having damage limited to cervical structures.     

Risk factors associated with Salmonella enterica subsp. enterica contamination of chicken carcases in Senegal

The objective of this study was to identify the risk factors for Salmonella spp. contamination of Senegalese chicken carcases during slaughtering. One hundred and twenty traditional slaughterhouses were studied from January 2000 to December 2002 in and around Dakar. A questionnaire was administered to the slaughterers and samples of breast skin were taken to assess the Salmonella spp. status of chicken carcases. Results showed that 43.3% of the chicken batches were contaminated with Salmonella spp., with Salmonella Hadar and Salmonella Brancaster as the two main serovars. Salmonella spp. contamination of the live birds before slaughtering was related to contamination of the carcases after slaughtering. Feed withdrawal before slaughtering and thorough cleaning and disinfection procedures decreased the risk of Salmonella contamination. One individual worker for each slaughtering stage was also associated with a decreased risk of Salmonella contamination. Using scalding water for plucking increased the risk of contamination. These results will help slaughterers to produce safer products for local consumers.     

Further monitoring for Salmonella species and Escherichia coli O86 at a bird table in south-west Scotland

Pooled faeces collected from a garden bird table were screened for Salmonella species and Escherichia coli O86, two recognised causes of garden bird mortality. Dead birds found at the site were also screened for these organisms, and bird numbers and meteorological data were recorded. In the first year of the study, 48.5 per cent of the samples were positive for Salmonella Typhimurium DT56 (variant), decreasing to 38.9 per cent in the second year and 12.8 per cent in the third year. E. coli O86 was not recovered from any of the 288 samples of pooled faeces tested. S. Typhimurium DT56 (variant) was recovered from the carcases of eight birds found dead at the site, and E. coli O86 was isolated from three carcases. The degree of contamination of the bird table with S. Typhimurium DT56 (variant) was positively correlated with the number of house sparrows observed in the garden, but not with the number of blackbirds, chaffinches or greenfinches.     

Postmortem condemnations of processed broiler chickens in western France

A total of 404 broiler chicken flocks processed in 15 slaughterhouses in western France were studied to estimate the condemnation prevalence and describe the official reasons for condemnation and the main macroscopic lesions observed in a sample of the condemned carcases. The condemnation rate was 87 per 10,000 birds slaughtered (95 per cent confidence interval 79 to 95 per 10,000) but differed significantly according to the type of poultry produced (standard, light, heavy or certified). The main reasons for condemnation were emaciation and congestion, with rates of 30 and 22 per 10,000 birds slaughtered, respectively. Congestion was significantly associated with arthritis and ascites, whereas infected skin lesions were associated with bruises and abnormalities of colour, odour or conformation.     

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.     

Risk factors for hide contamination of Scottish cattle at slaughter with Escherichia coli O157

In the slaughter processing of cattle, contaminated hides have been identified as one of the major sources of Escherichia coli O157 carcase contamination. Logistic regression analysis was applied to data collected in a large scale study in Scotland involving 222 cattle forming 34 groups sent for slaughter from 30 farms to 10 slaughterhouses. Aspects of individual animal characteristics, farm management practices and slaughterhouse features were examined to identify potential risk factors for hide contamination at harvest. Two models were developed, the first in which slaughterhouse was modelled as a fixed effect, and a second model where slaughterhouse and farm groups were modelled as random effects. In the first model, there was a significantly increased risk of a carcase testing positive for E. coli O157 on the hide if either the hide of the carcase immediately before or after it on the line was contaminated (OR 3.6; 95% CI: 1.4–9.9). If both adjacent carcases had contaminated hides, the odds ratio for the study carcase having a contaminated hide rose to 11.5 (95% CI: 4.4–32.5). If animals were held in lairage, receiving hay as feed appeared to have a protective effect on hide contamination. Transportation to the slaughterhouse by haulier, as opposed to transport by the farmer, was associated with a 5.4 increase in the odds of E. coli O157 contamination. The use of a crush in the lairage, often employed when reading ear tags, was also found to significantly increase the odds of hide contamination with E. coli O157. In the second model, the inclusion of slaughterhouse and farm group as random effects resulted in two of the previously identified factors being associated with hide contamination. If at least one of the adjacent carcases on the line had a contaminated hide, the associated odds ratio was 6.6 (95% CI: 2.8–15.9), which rose to 22.7 (95% CI: 9.3–55.5) if both adjacent hides were contaminated. Receiving hay in lairage was found to be important to the model, although not significant in itself (OR 0.005; 95% CI: 1.2e⁻⁶–20.7). These results suggest that modifiable risk factors for hide contamination exist. However, in order best to reduce the prevalence of hide contamination at slaughter, individual slaughterhouse risk assessment and intervention strategies are appropriate.