Flock infection and transport as sources of salmonellae in broiler chickens and carcasses.

Cultural monitoring was used to determine the incidence and sources of salmonellae in a 4160-bird broiler flock raised on litter in 32 pens. Twenty-five of the pens remained apparently free of salmonellae during the 49-day growing period. Salmonella johannesburg, first detected in the meat meal component of the starter ration, was recovered from the litter of seven pens and from the intestines of dead or culled chicks from two pens. Salmonella alachua was also recovered from two of these pens. Culture of swabs collected from the plastic crates used to transport this flock for processing showed that 97/112 (86.6%) were contaminated with salmonellae (15 serovars) before the birds were loaded. The crate washer at the plant did not remove salmonellae from these crates: 97/132 (73.5%) crates sampled after washing yielded salmonellae. Eleven serovar were recovered, including S. johannesburg and S. alachua introduced by the infected flock. Twelve of 31 chickens (38.7%) collected when the birds were unloaded at the processing plant were intestinal carriers of S. johannesburg and/or S. alachua and 29 (93.5%) were external carriers. Salmonella johannesburg, S. alachua and four other serovars were isolated from the feathers of these birds. Eleven of 25 (44%) carcasses tested from this flock yielded salmonellae. Salmonella johannesburg or S. alachua, first isolated from the infected flock, were recovered from five carcasses and S. haardt and S. Typhimurium, first isolated from the transport crates were recovered from six carcasses.     

The relationships of salmonellae from infected broiler flocks, transport crates or processing plants to contamination of eviscerated carcases.

Three flocks raised for broiler or roaster performance tests were studied to determine the incidence and sources of salmonellae during the growing period, transport and processing and to relate these to contamination of processed carcasses. Day old chicks in two of the tests, (tests IV and V), were treated with a culture of intestinal anaerobes derived from mature chickens. The incidence of salmonellae during the growing period was too low to permit any conclusions about the efficacy of this culture in preventing Salmonella infection, but it had no adverse effect on flock performance. Carcasses from all three flocks were contaminated with salmonellae. Although the test IV flock was raised free of salmonellae, 46% of the carcasses tested from this flock were contaminated. The apparent source was the transport crates, 99% of which yielded salmonellae before the flock was loaded. In test V, 92% of the carcasses tested yielded salmonellae. The apparent sources were: flock infection (apparently originating from the parent flock), contaminated crates, spread during transport, and plant contamination. The flock of test VI was infected with Salmonella albany, and 54% of the carcasses tested were contaminated with this serovar. Carcasses of chicks infected early in life were more likely to be contaminated than those of chickens which contacted salmonellae later in the growing period.     

Changes in the Salmonella status of broiler chickens subjected to simulated shipping conditions.

Market-age broiler chickens from flocks infected with Salmonella typhimurium were killed after being placed in crates and subjected to simulated shipping conditions for five, 19 or 24 hours. The cloacal feces, ceca and exteriors of the birds were cultured for salmonellae to identify shedders, cecal carriers and external carriers respectively, and the results compared with those obtained from pen-mates killed at the time the tested birds were put into the crates. Carriage of S. typhimurium was significantly higher among birds placed in clean crates than among the uncrated controls, mainly due to an increase in cecal carriers (from 23.5% to 61.5%). This increase was not related to the time spent in the crate. Twenty-four chickens were placed in crates contaminated with Salmonella alachua and all 24 became carriers of this organism: 22 (91.5%) of these were cecal carriers and 18 (75%) were shedders. This contamination also spread to 15/24 chickens placed in clean crates and "shipped" in the same truck: six of these became cecal carriers and seven were shedders. These results indicated that chickens in shipping crates which are exposed to salmonellae under transport conditions may readily become infected and begin to shed salmonellae within 24 hours.     

Incidence of salmonellae in domestic fowl in Slovakia from 1971 to 1980

In flocks with latent infections, 2724 strains of salmonellae (19 serotypes) were isolated from the birds. The following species were represented as follows: S. gallinarum-pullorum (65.08%), S. typhimurium (9.10%), S. bareilly (6.90%), S. enteritidis (2.38%) and S. agona (1.98%). In the foci of salmonelloses 893 strains of salmonellae (19 serotypes) were isolated. The highest representation was found in the S. gallinarum-pullorum (54.20%), S. typhimurium (24.53%), S. bareilly (7.72%), S. choleraesuis (2.29%), S. enteritidis (1.68%), S. infantis (1.54%) and S. anatum (1.23%). Post-mortem examination resulted in recording 15 887 strains of salmonellae (41 serotypes). The following were represented by the largest proportions: S. gallinarum-pullorum (26.62%), S. typhimurium (25.20%), S. bareilly (18.93%), S. infantis (7.20%), S. enteritidis (4.62%), S. agona (3.51%), S. choleraesuis (3.17%), S. anatum (2.19%), S. lille (1.54%) and S. bredeney (1.16%).     

Prevalence of Salmonella serotypes in pigs and evaluation of a rapid, presumptive test for detection of Salmonella in pig faeces

Two hundred faecal samples, collected from pigs at a Budapest abattoir, were examined for the presence of salmonellae. Ninety-six isolates, belonging to 7 different serotypes, were obtained. Salmonella derby (70.8%) was the most prevalent serotype. The other serotypes isolated were S. typhimurium (8.33%), S. bredeney (4.16%), S. agona (2.08%), S. infantis (9.22%), S. london (3.12%), and S. panama (2.08%). A modified rapid presumptive test to detect salmonellae in food and food ingredients was described by Hoben et al. (1973). This test medium was evaluated to determine its efficacy in detecting salmonellae in pig faecal samples. The test gave an efficiency of 88.67%. However, the incidence of false positive results was rather high (9.43%). The public health importance of the isolates obtained and the application of the rapid presumptive test at the farm level are discussed.     

Salmonella Contamination of the Product and Environment of Selected Canadian Chicken Processing Plants

Of 345 market chicken carcasses received directly from selected processing plants across Canada, six yielded salmonellae. One of the plants submitted 122 carcasses none of which yielded these organisms. A second plant had one Salmonella-contaminated carcass among 20 which were examined. Each of these two plants was subected to detailed bacteriological examinations on four occasions.

In these detailed examinations a total of 175 samples or specimens for culture were taken from a variety of surfaces including vent areas of carcasses, operators' hands, equipment surfaces and from water in tanks of iced birds. Twenty-five (14 per cent) of the cultures yielded salmonellae and all but one of these were either S. oranienburg or S. infantis. Isolations were made during five of the eight series of examinations. The evidence indicated that Salmonella-infected flocks were frequently slaughtered and that Salmonella contamination could become widespread in the plant during processing. The organisms are apparently eliminated from all but a small percentage of the carcasses during processing but opportunities exist for recontamination during subsequent handling.

     

Salmonellosis in breeds of pigs with latent infections and in salmonellosis foci

The occurrence of salmonellae in pigs in Slovakia is described for the period from 1971 to 1980. On the whole, 1430 strains (11 serological types) of salmonellae were isolated in stocks with latent infections. The proportions of the serological types were as follows: S. agona 0.69%, S. anatum 0.14%, S. arizona 0.07%, S. bareilly 0.14%, S. decatur 0.07%, S. enteritidis 1.12%, S. give 0.28%, S. heidelberg 0.07%, S. choleraesuis 93.71%, S. panama 0.07% and S. typhimurium 2.45%. In 1315 salmonellosis foci 1333 strains (six serological types) of salmonellae were isolated. The proportions of the serological types were as follows: S. agona 0.37%, S. anatum 0.07%, S. bareilly 0.22%, S. enteritidis 1.20%, S. choleraesuis 90.59% and S. typhimurium 5.30%. The annual pattern of the occurrence of the most frequent serological types is described.     

Therapeutic trials with native intestinal microflora for Salmonella typhimurium infections in chickens

Chicks infected with Salmonella typhimurium at 1 day of age were treated with normal intestinal flora starting 3 or 9 days later. Chicks were reared on the floor in isolated pens with wood shavings for litter. Cloacal-swab cultures were the main criteria for determining S. typhimurium infection. A single treatment reduced the infection period, but multiple treatments hastened the process considerably: after 6-8 weeks, birds given multiple treatments yielded sporadic or no isolations of S. typhimurium. It appears that litter from birds colonized by a protective microflora may serve as a vehicle for transmitting the flora to succeeding groups of birds.     

Serological response of chickens naturally infected with Salmonella typhimurium detected by ELISA.

Four laying flocks of chickens in Britain, each with a history of Salmonella typhimurium infection, were investigated serologically and bacteriologically. Blood samples were taken from identified birds from a single house on each site and sent to the Central Veterinary Laboratory, Weybridge for serological examination using enzyme-linked immunosorbent assays (ELISA) and rapid slide agglutination test (RST) using stained S. pullorum. The identified birds were taken to the local Veterinary Investigation Centre for bacteriological examination. On site A no salmonellae were recovered from birds in the house chosen for serological examination. Of these birds approximately 20% had antibodies to S. typhimurium in ELISA which used either a lipopolysaccharide (LPS) or heat-extract (HE) antigen from S. typhimurium. S. typhimurium was recovered from birds in one other of the four houses on the same site; these birds were not tested serologically. On site B, S. typhimurium was isolated from 8% of the birds examined. Of the total tested serologically, a third to half were seropositive by S. typhimurium ELISA using the LPS and HE antigen respectively. A small proportion of birds was seropositive by S. enteritidis ELISA and RST. No salmonellae were isolated from the other two sites although about 10% of birds tested on site C were seropositive in S. typhimurium ELISA. Cross-reactions were seen between S. typhimurium antigens in the ELISA and experimentally prepared antiserum to S. enteritidis. The S. enteritidis ELISA was generally more specific although cross-reacting antibodies were detected in sera from birds on sites A and B.     

Effects of feed withdrawal on the weight, fecal excretion and Salmonella status of market age broiler chickens.

The withdrawal of feed from the pens of broiler chickens for several hours before they are shipped for slaughter is an increasingly common practice, whose objective is to decrease fecal contamination of birds during processing. In this study, Salmonella typhimurium-infected market age broiler chickens were subjected to feed withdrawal for eight hours, then placed in crates for 18 hours before they were killed and weighed. The intestines, ceca, and cloacal feces were weighed and cultured for salmonellae. The feces deposited in the crates were also weighed and cultured. The results were compared with those of control birds whose feed was not withdrawn before they were placed in crates. The withdrawal of feed did not significantly affect the total liver weights of the birds, but reduced the weights of the intestines in 7/10 groups, and of the ceca in 5/11 groups, and dramatically reduced the amount of feces deposited in the crates. There was no consistent effect on excretion of salmonellae. These results indicated that feed withdrawal for eight hours before broilers are shipped for slaughter should be effective in reducing the spread of fecal contamination and of salmonellae during transport and processing, and in improving the effectiveness of crate washing procedures.     

Salmonella infection sources in poultry flocks in northern Greece]

From 10 egg production poultry farms 1516 samples were collected and examined for the presence of salmonella. The samples were: 201 chicken, 36 sparrows, 35 rats, 35 pools of 20 flies each, 450 eggs, 60 mattresses, 188 feces, 425 feedstuffs and 86 water samples. Salmonellae were isolated only from 163 (10.8%) samples. From the 146 (89.6%) of these S. gallinarum was isolated. From the rest 17 (10.4%) the following mobile salmonella strains were isolated: two strains of S. virchow and Salmonella of subgroup II, four strains of S. typhimurium var. Copenhagen, seven strains of S. Livingstone, one S. enteritidis and one S. infantis The S. gallinarum was isolated from dead or sick chicken (46%), eggs (10.4%), rats Rattus norvegicus (14.3%) and mattresses 1.6%. The mobile salmonellae were isolated from feedstuffs (2%), flies (14.3%), rats (2.8%), feces (1%). From the present study, it seems that rats, chicken and eggs are important for the salmonella dissemination.     

Incidence of Salmonella Contamination in Broiler Chickens in Saskatchewan

The incidence of Salmonella contamination in ten Saskatchewan broiler flocks varying in size from 6 200 to 14 000 was investigated from February, 1977 to April, 1979. Prior to the initial chick placement, brooding equipment, feed, water and fresh litter samples were found to be free of Salmonellae. Samples obtained from the clean and disinfected processing plant equipment before the commencement of daily operation were negative except the isolation for Salmonella anatum from the fingers of the defeathering machine in flock 4. There was no evidence of Salmonella contamination in flocks 5, 6, 8 and 10. The incidence of Salmonella was lower when cloacal swabs were taken from day old chicks fasted for 48 hours than for the same groups of chicks when carcasses were blended in nutrient broth (flocks 7 and 9). The blending of such chicks appears to be a more critical test. The serotypes isolated from eviscerated birds were the same as those isolated from used litter samples. Salmonella saintpaul was isolated from a water sample at 53 days in flock 1 and the same serotype was recovered from the intestinal contents and skin of eviscerated birds. Salmonella typhimurium was recovered from the eviscerated birds and neck samples in flock 3. In flock 4, S. saintpaul and S. anatum were isolated from 13% of the eviscerated birds sampled. Salmonella thompson, Salmonella agona and Salmonella heidelberg were recovered from 61%, 5% and 1%, respectively, of the processed carcasses sampled in flock 7.     

Prevalence and epizootiology of equine salmonellosis.

Feces from 1,451 horses entering a veterinary hospital over a 13-month period were cultured for salmonella. A total of 46 horses (3.2%) yielded 1 or more salmonella-positive fecal cultures. Twenty horses were found to be excreting salmonella in the feces on admission, and 5 of these later had severe diarrhea associated with enteric salmonellosis. Abdominal surgery and other severe stresses were associated with all cases of severe enteric salmonellosis. Serotypes of salmonella isolated included Salmonella agona (15), S anatum (14), S typhimurium (7), S typhimurium var copenhagen (4), S infantis (2), S montevideo (1), S meleagridis (1), S drypool (1), and an unnamed Salmonella serotype (1). Seven deaths were attributed to 4 serotypes (S typhimurium, 3; S anatum, 2; S typhimurium var copenhagen, 1; and S montevideo, 1). A marked seasonal incidence is isolations was found with isolations highest in later summer to early fall and lowest in the spring. It was also found that horses can shed salmonella intermittently, and a minimal of 5 consecutive negative fecal cultures is recommended before considering a horse not to be infected with salmonella.     

Isolation and characterisation of Salmonella in a turkey production facility

1. A comprehensive ecological survey was conducted from April 1997 to June 1999 on 4 turkey flocks (F1 to F4) to identify key pre-harvest sources/vectors of Salmonella colonisation. 2. Turkey caecal and crop content, litter, drinker, air, feed, feeder and environmental swab samples were collected. Conventional microbiological and serological procedures were used to isolate, identify, and confirm the presence or absence of Salmonella. 3. Salmonella was isolated from 13% of litter, 11% of turkey caeca, 10% of drinker, 5% of environmental swab, 3% of feed and 1% of feeder samples. Salmonella heidelberg (65%), S. senftenberg (19%), S. muenster (10%), S. anatum (3%), and S. worthington (3%) were identified. 4. Identifying environmental sources associated with Salmonella colonisation and characterising serotypes would assist in designing pre-harvest controls for this poultry-borne pathogen. Integrators and poultry producers may be able to design hazard analysis and critical control point (HACCP) protocols to reduce the incidence of Salmonella arriving at the processing plant.     

Epizootiology of Salmonella typhimurium infection in chickens]

The incidence of S. typhimurium infections among fowl increased in thr region of Potsdam in general, and on various big farms in particular, 1976 and over the first half of 1977. The outbreaks included subclinical infections and clinically manifest diseases which caused remarkable loss of broilers from the affected stocks (up to 15.92 per cent). Parent stocks contaminated with S. typhimurium were to be the sources of infection in all cases. A total of 1,220 Salmonella strains were isolated from fowl and its environment, with 1,151 of them being S. typhimurium (2.98 per cent of all samples tested). The following amounts of S. typhimurium strains were isolated from different types of samples which had been collected from infected broiler stocks: 8.10 per cent from dead broilers, 5.86 per cent from dead broiler parents, 2.11 per cent from pulp linings of transport cages for day-old chicks, 1.23 per cent from litter, 1.0 per cent from hatching material (eggs or dead and jammed embryos, and 0.12 per cent from swabs used in hygiene supervision). No Salmonellae were isolated from feedstuff. The transmission of S. typhimurium, therefore, is though to have taken the route via the hatching egg and via congenitally infected chicks traded between breeders and propagation farms. The control and prophylaxis of S. typhimurium infections, therefore, should be based primarily on action in the centralised breeding stocks. Specific steps of such action are proposed. Fifty-three strains were biochemically and lysotypically analysed, with the following types being determined: ut/Ph 30 BT b, ut/Ph 30 BT c, n.c. 1/72/n.c. BT b, 2 n.c. BT a, and 1A/6 BT a. The first two types covered 84.9 per cent of all strains isolated from the fowl. All lysotype ut/Ph 30 strains isolated from fowl fell under the copenhagen variant which had rarely been isolated from man in the past. These results are likely to support the demand for a joint control programme for enteritis Salmonellae, with particular emphasis on S. typhimurium, for implementation in human and veterinary medicine.     

A national survey to estimate the prevalence of Salmonella species among Canadian registered commercial turkey flocks.

In 1990-1991, a national survey was conducted to estimate the prevalence of Salmonella species among Canadian commercial turkey flocks. Two hundred and seventy flocks were randomly selected across Canada. The proportion sampled from each province was selected according to each province's share of the national turkey market. Samples, consisting of 12 pooled litter and four pooled dust samples, were used to determine the Salmonella status of the environment of each flock. Additionally, a one kilogram sample of feed was taken from each flock premise. Salmonella was recovered from environmental samples in 234/270 (86.7%) of flocks and from feed samples in 26/266 (9.8%) of flocks. Forty-eight different Salmonella serovars were isolated from flock environmental samples. The most prevalent serovars were S. anatum, S. hadar, S. agona, S. heidelberg and S. saintpaul which were isolated from 53/270 (19.6%), 49/270 (18.1%), 49/270 (18.1%), 42/270 (15.6%) and 34/270 (12.6%) flocks, respectively.     

Seroprevalence and antibiotic sensitivity of serotypes of Salmonella enterica in Greek pig herds

Blood samples were taken from 50 pigs in each of 59 farrow-to-finish production herds and from 40 pigs in each of four of five registered multiplying herds. Samples of feed and faeces were also collected from 17 of the production herds and from the four multiplying herds. The sera were tested for antibodies to Salmonella enterica by the Danish mix-ELISA, and the organisms were isolated, serotyped and sensitivity tested by standard techniques. The average within-herd seroprevalence was 3.4 per cent and at least one pig tested seropositive in 21 of the 59 herds. In the multiplying herds, only a single seroreactor was detected. Salmonellae were isolated from only five of 95 feed samples, from two of the 17 herds sampled, Salmonella tennessee in four of five samples from one herd and an untypable strain in one of five samples from another. Four infected faecal samples were detected in four herds; they harboured Salmonella typhimurium, Salmonella bredeney or Salmonella london. No salmonellae were isolated from the samples of feed and faeces taken from the multiplying herds. The S london and S typhimurium had a low sensitivity to streptomycin, kanamycin and neomycin, and the S typhimurium also had low sensitivity to amoxycillin, ticarcillin, piperacillin, amoxycillin + clavulanic acid, cefalotin and cefoperazone. The other isolates were sensitive to all the antimicrobial agents tested.     

Pathogenicity of different serogroups of avian salmonellae in specific-pathogen-free chickens.

The pathogenicity of one isolate of Salmonella typhimurium, four isolates of Salmonella heidelberg, three isolates of Salmonella kentucky, two isolates of Salmonella montevideo, one isolate of Salmonella hadar, and two isolates of Salmonella enteritidis (SE), one belonging to phage type (PT)13a and the other to PT34, was investigated in specific-pathogen-free chicks. Three hundred eighty-four chicks were separated into 16 equal groups of 24 chicks. Thirteen groups were inoculated individually with 0.5 ml of broth culture containing 1 x 10(7) colony-forming units (CFU) of either S. typhimurium (one source), S. heidelberg (four sources), S. montevideo (two sources), S. hadar (one source), S. kentucky (three sources), SE PT 13a (one source) or SE PT 34 (one source) by crop gavage. Two groups of 24 chicks were inoculated in the same way with 1 x 10(7) CFU of SE PT4 (chicken-CA) and Salmonella pullorum. Another group of 24 chicks was kept as an uninoculated control group. The chicks were observed daily for clinical signs and mortality. Isolation of salmonella was done from different organs at 7 and 28 days postinoculation (DPI). All the chicks were weighed individually at 7, 14, 21, and 28 DPI. Two chicks chosen at random from each group were euthanatized and necropsied at 7 and 14 DPI and all the remaining live chickens, at 28 DPI. Selected tissues were taken for histopathology at 7 and 14 DPI. Dead chicks were examined for gross lesions and tissues were collected for histopathology. Chicks inoculated with S. pullorum had the highest mortality (66.66%), followed by S. typhimurium (33.33%). Chicks inoculated with S. heidelberg (00-1105-2) and SE PT4 (chicken-CA) had 12.5% mortality and 8.3% mortality, respectively, with SE PT 13a. Ceca were 100% positive for salmonellae at acute or chronic infection compared with other organs. Mean body weight reduction ranged from 0.67% (inoculated with S. kentucky 00-926-2) to 33.23% (inoculated with S. typhimurium 00-372) in the inoculated groups at different weeks compared with uninoculated controls. Gross and microscopic lesions included peritonitis, perihepatitis, yolk sac infection, typhilitis, pneumonia, and enteritis in some groups, especially those inoculated with S. typhimurium, S. heidelberg (00-1 105-2), SE PT4 (chicken-CA), and S. pullorum.     

Evaluation of Salmonella serotype distributions from commercial broiler hatcheries and grower houses

By conventional trayliner (hatcheries) and drag swab assembly (broiler houses) culture methods, the isolation distribution of Salmonella serotypes from five commercial broiler hatcheries (three sample times) and 13 broiler farms (eight sample times) was evaluated. A total of 11 different Salmonella serotypes were isolated from hatcheries, with Salmonella heidelberg (9/30) and Salmonella kentucky (6/30) accounting for 50% of the total isolations. Of 700 chick paperpad trayliners sampled, regardless of lot (breeder flock source) or hatchery, 12% were positive for Salmonella. When 10 individual trayliners were cultured from individual lots (same breeder flock source), Salmonella was detected in 24/57 lots (42%). Multiple serotypes were simultaneously isolated from the same lot on three occasions (6%). Of the 21 lots that were serially sampled, the Salmonella serotype detected was different within lots eight times (38%) on at least one occasion of two or more sampling times. Of the 196 individual broiler houses sampled, 44 were positive for Salmonella (42%). Twelve different serotypes were isolated from broiler houses during this study. The serotypes isolated most frequently were S. heidelberg (34/94) and S. kentucky (22/94). These two serotypes accounted for 59.6% (56/94) of the total broiler house isolations. Of the 38 houses that were serially sampled, two or more serotypes were detected in the same broiler house on 20 occasions (53%). Of the 38 serially sampled houses (four or more times), a consistent Salmonella serotype was detected in five houses (13%). In only 5 of the 38 (13%) serially sampled houses did we fail to detect Salmonella on four or more samplings. No significant difference in Salmonella isolation frequency was observed between poultry houses using new or used litter. These data support previous findings indicating that paratyphoid Salmonella serotypes are prevalent in some broiler hatcheries and houses. Further, the observation of multiple serotypes simultaneously and serially isolated from the same breeder hatchery lots suggests that breeder flocks may be infected with more than one serotype, possibly providing a source for multiple serotype infections in progeny grower flocks.     

The prevalence of verocytotoxin-producing Escherichia coli and antimicrobial resistance patterns of nonverocytotoxin-producing Escherichia coli and Salmonella in Ontario broiler chickens.

The prevalence of verocytotoxin-producing Escherichia coli and Salmonella in Ontario broiler chickens was determined by culturing cloacal samples from 500 individual birds selected from 50 poultry farms. Resistance to antimicrobials was determined for each of the isolates. In addition, abattoir and farm-level management data were obtained to evaluate variables that may be considered risk factors for infection. The variables selected included: Percentage of birds condemned at slaughter, percentage of birds dead-on-arrival, bird weight, truck number, farm size, hatchery source, litter source and type, feed source, mortality levels, type of water drinker, water sanitization, down time, barn clean out and history of antibiotic treatment. None of the cloacal samples revealed the presence of verocytotoxin-producing E. coli, though 19/500 (3.8%) contained Salmonella organisms. Nine different Salmonella serotypes were isolated; the most common being S. hadar, S. heidelberg and S. mbandaka. Resistance to tetracycline and streptomycin was common among Salmonella (63%) and E. coli (25.2%) isolates. Resistance to two or more antimicrobials occurred in 420/500 (84%) of the E. coli isolates. No statistically significant associations between abattoir or farm-level management variables and the Salmonella-status of farms were demonstrated.