Meat safety legislation and its opportunities and hurdles for innovative approaches: A review.

Albert Einstein has been quoted "We cannot solve our problems with the same thinking we used when we created them". Innovations are necessary to meet future challenges regarding sustainability, animal welfare, slaughter hygiene, meat safety and quality, not at least for optimal balance between these dimensions. The red meat safety legislation texts from Europe, New Zealand, USA, and global guidelines, were analysed for normative formulations ("how it is or should be done") that may create non-intentional hurdles to innovation and new technology. Detailed descriptions of slaughtering techniques and meat processes may hinder innovative processing from being investigated and implemented. The identified problematic normative phrases typically either conserve conventional technologies or organisation of the work, prescribe solutions where no established method, objective criteria or limits exits, or put forward visions impossible to obtain. The Codex Alimentarius was found to have less normative formulations and more functional demands ("what to achieve") than the national and regional regulations. European, New Zealand's and US' legislation share many similarities and challenges, and they all reflect the prevailing processing methods. Consequences are briefly commented, and alternative objective functional demands suggested. Normative legislation texts provide familiar context easier to understand, but also make legislation voluminous. This review underlines the mutual dependency between risk-based legislation and conditional flexibility, and between functional demands and control activities targeted on measurable objective criteria. The legislation does not have to be either or. Objective normative phrases in legislation can function as a least common multiple if alternative methods are allowed on condition that they fulfil objective criteria. Context and practical advice should mainly come from textbooks, consultants, white papers and in Food Business Operator's own guidelines, among others.

Beyond standard PSE testing: An exploratory study of bioimpedance as a marker for ham defects.

During post-mortem conversion from muscle to meat, diverse quality anomalies can emerge. Recent pork defects are often accompanied by deteriorating fibre structure. Here we investigate how bioimpedance response, an indicator of structural disintegration, can help in detecting quality defects. We, first, measured the relationship between standard meat quality variables (pHu, CIELAB, drip loss) and bioimpedance (BI) response. To screen for defect-biomarkers that are linked to aberrant bioimpedance and physicochemical indicators of quality decline, we performed LC-MS/MS proteomic analysis on samples, classified with a multivariate-based separation into good versus poor quality. We found that BI correlated significantly with, e.g., colour and drip loss. Proteomics revealed eleven proteins to be unique for either, good or poor ham quality groups, and maybe linked to structural degradation. In all, our data supports a wider integration of BI testing in pork quality testing to assess structural disintegration, which can render ham unsuitable for, e.g., costly curing.

A European survey on post-mortem inspection of finishing pigs: Total condemnation criteria to declare meat unfit for human consumption.

Meat inspection (MI) is essential to verify compliance with legal requirements related to human and animal health and animal welfare protections. Judgement criteria applied during MI, resulting in condemnation data of importance, among other things, for livestock producers and for benchmarking reasons. However, although the Meat Inspection Regulation sets out judgement criteria, most are generic, favouring flexibility, but also subjectivity. To address the degree of variation on total condemnation (TC) criteria applied during post-mortem inspection (PMI) of finishing pigs, an online survey was prepared aiming to collect this information from several European countries. The focus was on TC criteria regarding the following PMI findings: abscesses, arthritis, cachexia, erysipelas, icterus, Mycobacterium-like lesions, osteomyelitis, peritonitis, pleuritis and pneumonia. From September to November 2020, a total of 44 completed questionnaires were obtained from 26 European countries. The results showed a substantial variation in the TC criteria in place in the participating countries. One of the main reasons for the variability seen in the respondents' reported answers was related to the indicators used to define a generalised condition related to the 10 PMI findings addressed, making harmonisation a challenge and avoiding to draw conclusions when comparing condemnation causes between abattoirs. This implies that it would make sense to look into how a generalised condition can be identified/described and how it should be judged. The results should be used as inspiration towards possible harmonisation, improving decision-making, and permitting comparative analysis between different reports to allow trend analyses and benchmarking.

Microbiological Safety and Shelf-Life of Low-Salt Meat Products-A Review.

Salt is widely employed in different foods, especially in meat products, due to its very diverse and extended functionality. However, the high intake of sodium chloride in human diet has been under consideration for the last years, because it is related to serious health problems. The meat-processing industry and research institutions are evaluating different strategies to overcome the elevated salt concentrations in products without a quality reduction. Several properties could be directly or indirectly affected by a sodium chloride decrease. Among them, microbial stability could be shifted towards pathogen growth, posing a serious public health threat. Nonetheless, the majority of the literature available focuses attention on the sensorial and technological challenges that salt reduction implies. Thereafter, the need to discuss the consequences for shelf-life and microbial safety should be considered. Hence, this review aims to merge all the available knowledge regarding salt reduction in meat products, providing an assessment on how to obtain low salt products that are sensorily accepted by the consumer, technologically feasible from the perspective of the industry, and, in particular, safe with respect to microbial stability.

Understanding metabolic phenomena accompanying high levels of yeast in broiler chicken diets and resulting carcass weight and meat quality changes.

The use of yeast as a protein source was investigated in broiler chicken diets on carcass quality, storage stability, and metabolite changes in leg meat. Male Ross 308 chickens (n = 100) were fed with one of 5 diets: control, control added 0.6% formic acid, or 3 diets where soybean meal was substituted with 10, 20, and 30% crude protein from inactivated yeast Cyberlindnera jadinii (CJ10, CJ20, CJ30, respectively). The yeast-containing diets reduced carcass weight, linoleic acid, and warm-over flavor in chicken leg meat. Protein degradation-related metabolite biomarkers were upregulated in the leg of chickens that were fed yeast-containing diets, indicating an adaptive response to the loss of appetite. Chill-stored leg meat of birds fed yeast diets showed increased browning and metallic taste compared with those fed the control diet. The use of formic acid in the diet reduced cooking loss and had a positive effect on vitamin B content.

Pigs: A stepwise RGB-D novel pig carcass cutting dataset.

This paper presents a pig carcass cutting dataset, captured from a bespoke frame structure with 6 Intel® RealSense™ Depth Camera D415 cameras attached, and later recorded from a single camera attached to a robotic arm cycling through the positions previously defined by the frame structure. The data is composed of bags files recorded from the Intel's SDK, which includes RGB-D data and camera intrinsic parameters for each sensor. In addition, ten JSON files with the transformation matrix for each camera in relation to the left/front camera in the structure are provided, five JSON files for the data recorded with the bespoke frame and five JSON files for the data captured with the robotic arm.

Development and validation of a regression model for Listeria monocytogenes growth in roast beefs.

Food business operators are responsible for food safety and assessment of shelf lives for their ready-to-eat products. For assisting them, a customized software based on predictive models, ListWare, is being developed. The aim of this study was to develop and validate a predictive model for the growth of Listeria monocytogenes in sliced roast beef. A challenge study was performed comprising 51 different combinations of variables. The growth curves followed the Baranyi and Roberts model with no clear lag phase and specific growth rates in the range <0.005-0.110 hr-1. A linear regression model was developed based on 528 observations and had an adjusted R-square of 0.80. The significant predictors were storage temperature, sodium lactate, interactions between sodium acetate and temperature, and MAP packaging and temperature. The model was validated in four laboratories in three countries. For conditions where the model predicted up to + log 2 cfu/g Listeria concentration, the observed concentrations were true or below the predicted concentration in 90% of the cases. For the remaining 10%, the roast beef was coated with spices and therefore different from the others. The model will be implemented in ListWare web-application for calculation of "Listeria shelf life".

Intact gastro-intestinal tract removal from pig carcasses in a novel Meat Factory Cell approach.

Conventional automated slaughter lines for pigs are organised as disassembly lines with many specialised machines. High costs and capacities make them relevant only for large scale meat production. The ambition with the novel Meat Factory Cell (MFC) concept is to provide the meat industry with a robust and flexible automation platform that is also relevant for smaller scale production. The MFC process deviates radically from conventional processing of pig carcasses after singeing. In MFC, the limbs are removed first. Then the dorsal muscles along the spinal axis from tail to head are removed with the column and rind in one meat cut, followed by removal of the viscera. Finally, the cut ribs and belly are removed. Such approaches to automation in pig abattoirs and cutting plants are highly needed in smaller scale production, and they should produce meat and offal as hygienically as conventional factories. This case study reports the evisceration of 37 pigs in 9 trials performed in 2019. Several approaches were tested with a prototype carcass holding unit. Evisceration could be undertaken without the need to cut through the gastrointestinal tract from tongue to rectum, reducing the probability of accidental faecal contamination of pork carcasses from the gut content. The Meat Factory Cell procedure is an advance towards automated evisceration of pig carcasses which is both simple and hygienic. The traditional separation of internal organs into a pluck set and a set of stomach and bowels was more prone to leakages.

A Systematic Review of Bacterial Foodborne Outbreaks Related to Red Meat and Meat Products.

Our investigation focused on foodborne outbreaks related to meat and meat products, published in peer-reviewed journals in the period 1980-2015. Most of the outbreaks, investigated in this study, were caused by Escherichia coli and Salmonella, causing 33 and 21 outbreaks, respectively, mostly in Europe and the United States. In the E. coli outbreaks, the total number of reported cases was 1966, of which 1543 were laboratory confirmed. The number of cases requiring hospitalization was 476, of whom 233 cases had a hemolytic-uremic syndrome (HUS), and the reported deaths were 32. All of the E. coli outbreaks, except four, were caused by serovar O157:H7. The other four outbreaks were caused by the following serovars: O111:H8, O26:H11, O111, and O103:H25. Fresh processed meat products were the category most frequently implicated. In the Salmonella outbreaks, the total number of all reported cases was 2279, of whom 1891 were laboratory confirmed. The number of reported cases requiring hospitalization was 94, and seven were reported dead. Regarding Salmonella, eight serovars caused those outbreaks. The most common serovar causing Salmonella-related outbreaks was Salmonella Typhimurium. The food category most frequently implicated in those outbreaks was raw-cured fermented sausages. Other organisms linked to meat-associated outbreaks, but less frequently reported, were Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Clostridium botulinum, and Listeria monocytogenes. Issues of the burden of outbreaks, the challenges of comparing global outbreaks, food attribution, and how the meat industry works to meet consumer demands while maintaining food safety are discussed.

Monitoring lean meat percentage predictions from optical grading probes by a commercial cutting pattern.

The lean meat percentage (LMP) classification in Norwegian slaughterhouses is obtained by Hennessy Grading Probe 7 (HGP7), an optical tool. Even though the HGP7 method is validated frequently, there is industrial and legislative demand to reconsider the applied LMP equation, typically due to the introduction of new breeds. A deboning pilot plant generates precise yield data using cutting and deboning stratified pork carcasses by a specific commercial cutting pattern (CCP) at an annual rate of approximately 250 slaughter pigs. This paper shows how results obtained by CCP can be used to measure LMP in pork and how these results can be used for monitoring the quality of LMP predicted by HGP7. The effect of gender, maternal- and paternal lines on validity of HGP7 predictions was evaluated. The effect of introducing a new maternal line (TN70) seems to be substantial, whereas the effects of the tested paternal lines are small to negligible.

A comparison of two evisceration methods on hygienic quality in the pelvic area of sheep carcasses.

The aim was to compare the effects of two evisceration methods under operational conditions, on the pelvic hygiene of sheep carcasses. Method 1: rectum sealed with plastic bag and pushed through the pelvic cavity. Method 2: rectum cut, placed back inside and pulled out from the carcass. The 18 largest Norwegian sheep abattoirs participated. Sampling areas were i) 400cm2 inside the pelvic cavity (n=623), ii) 100cm2 outside the circum-anal incision (n=622). There were pooled samples by swabbing the same area of five carcasses, representing totally 3115 carcasses. Mean E. coli results from Method 1: -1.61logCFU/cm2 inside and -0.25logCFU/cm2 for the outside area. Results from Method 2: -1.56logCFU/cm2 inside and -0.42logCFU/cm2 outside. There were no significant differences between the two methods. Both evisceration methods can produce carcasses that are of practically identical high hygienic quality.

Enumeration of Escherichia coli in swab samples from pre- and post-chilled pork and lamb carcasses using 3M™ Petrifilm™ Select E. coli and Simplate® Coliforms/E. coli.

The aim of the study was to compare two analytical methods; 3M Petrifilm™ Select E. coli and SimPlate® Coliforms &E. coli, for detection and enumeration of E. coli using swab samples from naturally contaminated pork and lamb carcasses that were collected before and after chilling. Blast chilling was used for pork carcasses. Swab samples (n=180) were collected from 60 warm and 60 chilled pork carcasses, and 30 warm and 30 chilled lamb carcasses, and analysed in parallel. The concordance correlation coefficient between Petrifilm and SimPlate was 0.89 for pork and 0.81 for lamb carcasses. However, the correlation was higher for warm carcasses (0.90) than chilled carcasses (0.72). For chilled lamb carcasses, the correlation was only 0.50, and SimPlate gave slightly higher results than Petrifilm (P=0.09). Slower chilling gave slightly lesser agreement between methods than for blast chilling, however, both Petrifilm and SimPlate methodologies are suitable and recommended for use in small laboratories in abattoirs.

Effects of dietary beef, pork, chicken and salmon on intestinal carcinogenesis in A/J Min/+ mice.

The International Agency for Research on Cancer has classified red meat as "probably carcinogenic to humans" (Group 2A). In mechanistic studies exploring the link between intake of red meat and CRC, heme iron, the pigment of red meat, is proposed to play a central role as a catalyzer of luminal lipid peroxidation and cytotoxicity. In the present work, the novel A/J Min/+ mouse was used to investigate the effects of dietary beef, pork, chicken, or salmon (40% muscle food (dry weight) and 60% powder diet) on Apc-driven intestinal carcinogenesis, from week 3-13 of age. Muscle food diets did not differentially affect carcinogenesis in the colon (flat ACF and tumors). In the small intestine, salmon intake resulted in a lower tumor size and load than did meat from terrestrial animals (beef, pork or chicken), while no differences were observed between the effects of white meat (chicken) and red meat (pork and beef). Additional results indicated that intestinal carcinogenesis was not related to dietary n-6 polyunsaturated fatty acids, intestinal formation of lipid peroxidation products (thiobarbituric acid reactive substances, TBARS), or cytotoxic effects of fecal water on Apc-/+ cells. Notably, the amount of heme reaching the colon appeared to be relatively low in this study. The greatest tumor load was induced by the reference diet RM1, underlining the importance of the basic diets in experimental CRC. The present study in A/J Min/+ mice does not support the hypothesis of a role of red meat in intestinal carcinogenesis.

Theoretical Basis and Application for Measuring Pork Loin Drip Loss Using Microwave Spectroscopy.

During cutting and processing of meat, the loss of water is critical in determining both product quality and value. From the point of slaughter until packaging, water is lost due to the hanging, movement, handling, and cutting of the carcass, with every 1% of lost water having the potential to cost a large meat processing plant somewhere in the region of €50,000 per day. Currently the options for monitoring the loss of water from meat, or determining its drip loss, are limited to destructive tests which take 24-72 h to complete. This paper presents results from work which has led to the development of a novel microwave cavity sensor capable of providing an indication of drip loss within 6 min, while demonstrating good correlation with the well-known EZ-Driploss method (R² = 0.896).

The significance of clean and dirty animals for bacterial dynamics along the beef chain.

This study investigated the bacterial dynamics along the beef chain for clean and dirty cattle in the slaughter and processing lines, using classic quantitative methods and molecular analyses. In addition, the Norwegian national guidelines for Good Hygiene Practices in Norway were evaluated. In these guidelines, cattle presented for slaughter are categorised according to hide cleanliness, resulting in separate processing lines for meat from very dirty animals and reduced prices to farmers. The study was conducted in two commercial abattoirs in Norway. Two groups were compared; 40 visually clean cattle and 40 visually dirty cattle presented for slaughter, with 20 from each group at each abattoir. The same animals were sampled at five sampling sites: hides, carcass surfaces after dehiding, just before chilling, after chilling, and meat trimmings. Meat trimmings were sampled in only one abattoir. Three hundred and sixty samples were collected by swabbing 100 cm(2) of the brisket area at the first four sampling sites, and sampling 200 g of meat trimmings at the fifth site. The results showed that the hides of dirty cattle had more Enterobacteriaceae and higher Aerobic Plate Counts (APC) than visually clean cattle (P<0.05), however there was no significant difference for Escherichia coli. For the other sampling sites, there were no differences between the dirty and the clean group. An effect of chilling/drying of the carcass surfaces was demonstrated by the significant reduction in the number of carcasses on which E. coli and Enterobacteriaceae were detected; from 11% and 39% before chilling to 1% and 16% after chilling, respectively. Enterobacteriaceae and E. coli were detected in only three and one of the meat trimming samples, respectively. Amplification and sequencing of the 16S rRNA gene from 643 Enterobacteriaceae colonies derived from 107 samples demonstrated that Escherichia/Shigella were dominant within this family on the hides. However, after dehiding, after grading, and after chilling, the genera Citrobacter and Enterobacter dominated. The meat trimmings were dominated by the genera Kluyvera, Hafnia, and unclassified Enterobacteriaceae. The relative proportions of Escherichia/Shigella were higher for dirty animals than for clean animals, and were higher on hides than from sampling sites further down the chain (P<0.05). The minor differences in contamination on carcass surfaces and meat trimmings between clean and dirty cattle indicate that separate processing lines in Norwegian abattoirs seem to be unnecessary.

Effects of hygienic treatments during slaughtering on microbial dynamics and contamination of sheep meat.

The aims of this study were to investigate bacterial dynamics in the sheep meat chain, from fleece to meat trimmings, using both quantitative and qualitative analyses, and to study the effects on microbial load associated with the hygienic interventions of: i) shearing sheep immediately before slaughter, ii) manual steam vacuum pasteurisation, iii) hot water pasteurisation of carcasses, followed by iv) chilling. A further aim was to provide evidence to determine whether or not unshorn sheep should be handled in a processing line separate from that of shorn sheep in Norwegian abattoirs. A total of 176 surface swab samples were collected from three sites along the value chain: i) on fleeces, ii) on carcasses at the end of the slaughter line, and iii) on carcasses after chilling for 24h, and 32 samples were collected from meat trimmings. The results showed that Aerobic Plate Counts (APC) were lower for the shorn group compared to the unshorn group, both on carcasses before chilling and after chilling (difference of 0.8 and 0.9logCFU/1000cm(2) (p≤0.05), respectively) and in meat trimmings (difference of 0.5logCFU/g (p≤0.05)). Hygienic treatments were used on carcasses derived from unshorn sheep, and steam vacuum treatment reduced Escherichia coli, Enterobacteriaceae, and APC before chilling by 1.2, 1.0, and 0.6logCFU/1000cm(2) (p≤0.05), respectively, and hot water pasteurisation, in addition to chilling, reduced E. coli, Enterobacteriaceae, and APC by 0.7, 1.0, and 0.9logCFU/1000cm(2) (p≤0.05), respectively, compared with untreated carcasses. The effect of chilling was shown by the significant reduction of number of carcasses where E. coli were detected; from 65% (13/20) of the shorn group before chilling to 35% (7/20) after chilling, and from 90% (36/40) to 45% (9/20) of the unshorn group. Sequencing of the 16S rRNA gene derived from 316 colonies of Enterobacteriaceae showed a tendency for the relative proportion of the genus Escherichia/Shigella, compared with other genera within Enterobacteriaceae, to be greater for unshorn, untreated sheep than from the other groups at the sampling locations along the meat chain. The study showed that steam vacuum and hot water pasteurisation reduced the contamination of carcasses derived from unshorn sheep, down to the level of the shorn group, and thus can replace the separate processing line for unshorn sheep. Indeed, the low microbial contamination in meat trimmings for all groups indicates that the separate processing line is unnecessary.

Effect of intramuscular fat, breed, and age at slaughter on fatty acid composition in green hams.

UNLABELLED: The evolution of fatty acid classes (ΣSFA, ΣMUFA, and ΣPUFA) in neutral lipids (NL) and phospholipids (PL) in pigs were studied. The M. biceps femoris in green hams from Norwegian breeds Landrace (LR), Duroc (DU), and Hampshire (HS) slaughtered at 6, 7.5, and 9 mo of age were examined. The parameters were analyzed for age and breed effects with and without adjustment for NL or PL content. The fatty acid class contents of NL were not significantly different between the age groups. However, when NL content was adjusted, deposition of ΣSFA and ΣMUFA in NL significantly increased and deposition of ΣPUFA in NL significantly decreased with age. Duroc had consistently higher fatty acid class contents, but after adjusting for NL content, only the deposition of ΣSFA proved to be genetically different. The nonlinear relationship between NL content and ΣMUFA and ΣPUFA, together with the genetic potential of HS to deposit less ΣSFA than LR, gave significantly different fatty acid class compositions between the breeds. The content and proportion of ΣMUFA in PL increased with age. Specific ratios were also determined. The fat firmness index, C18:0/C18:2n - 6 in NL, increased with age and was lowest in HS due to genetics and highest in DU due to its high NL content. The sensory rancidity index C18:1n - 9/Σn - 6 increased in NL and decreased in PL between 7.5 and 9 mo. The C18:1n - 9/Σn - 6 in NL was highest in DU due to higher NL content. The Σn - 6/Σn - 3 in NL and PL increased between 7.5 and 9 mo. PRACTICAL APPLICATION: Knowledge of age-related changes and breed differences in fat content and composition would be helpful in determining the optimal breed and slaughter time in terms of raw ham quality.

Reduction of verotoxigenic Escherichia coli in production of fermented sausages.

After a number of foodborne outbreaks of verotoxigenic Escherichia coli involving fermented sausages, some countries have imposed regulations on sausage production. For example, the US Food Safety and Inspection Service requires a 5 log(10) reduction of E. coli in fermented products. Such regulations have led to a number of studies on the inactivation of E. coli in fermented sausages by changing processing and post-processing conditions. Several factors influence the survival of E. coli such as pre-treatment of the meat, amount of NaCl, nitrite and lactic acid, water activity, pH, choice of starter cultures and addition of antimicrobial compounds. Also process variables like fermentation temperature and storage time play important roles. Though a large variety of different production processes of sausages exist, generally the reduction of E. coli caused by production is in the range 1-2 log(10). In many cases this may not be enough to ensure microbial food safety. By optimising ingredients and process parameters it is possible to increase E. coli reduction to some extent, but in some cases still other post process treatments may be required. Such treatments may be storage at ambient temperatures, specific heat treatments, high pressure processing or irradiation. HACCP analyses have identified the quality of the raw materials, low temperature in the batter when preparing the sausages and a rapid pH drop during fermentation as critical control points in sausage production. This review summarises the literature on the reduction verotoxigenic E. coli in production of fermented sausages.

The agreement in isolation of Salmonella enterica IIIb 61:k:1,5,(7) from rectal swabs, faecal samples and ileo-caecal lymph nodes from sheep.

The agreements between various culturing-method combinations and specimens to detect sheep naturally infected by Salmonella enterica IIIb 61:k:1,5,(7) were tested. Rectal swabs, faecal samples and ileo-caecal lymph nodes were collected from each individual. Rectal swabs called "group I" (n = 54) were cultured directly on selective media (selenite cysteine, SC). Rectal swabs called "group II" (n = 47) were pre-incubated in buffered peptone water. The four other combinations of culturing-method and specimen (one lymph node and three faecal) in each of the two groups were cultured directly on SC. The results from all the combinations of method and specimens were compared to the result from the rectal-swab test by kappa and McNemar's chi-square. Kappas for the agreement between rectal swabs and faecal sample tests were only 0.4. The lymph-node test agreed even-more poorly, with mean kappa value -0.02. The McNemar's test revealed that the discordancies between the rectal-swab test and all of the other tests went in both directions but sometimes did show bias (directionality) in the discordancies.

The prevalence and dynamics of Salmonella enterica IIIb 61:k:1,5,(7) in sheep flocks in Norway.

Fifty randomly selected sheep flocks from a region in central Norway were sampled in December 1999 to determine the flock prevalence of Salmonella enterica subspecies diarizonae serovar 61:k:1,5,(7) (S. IIIb 61:k:1,5,(7)). From each flock, 15-41 rectal swabs were collected from individual sheep of different age groups and examined for S. IIIb 61:k:1,5,(7). Positive flocks were visited again in January-April and each time, rectal swabs from the same animals were collected and examined for this specific serovar. Seven flocks (14%; 95% CI 6.3-27%) were positive for S. IIIb 61:k:1,5,(7) in December; in all, 10 sheep out of the 1233 (0.8%) were positive at the first sampling. From the seven positive flocks, six, five, six, and nine animals were positive in January, February, March, and April, respectively. Of the total 21 individual sheep tested positive from January to April, 15 were >2 years old (OR(ex)=3.26; 1.1-10.2). Six out of the seven positive flocks were large flocks (>117 ewes). Sharing of rams between flocks did not seem to be a risk factor for the presence of S. IIIb 61:k:1,5,(7) in a flock.