An outbreak of disease due to chicken anaemia agent in broiler chickens in England

Outbreaks of clinical chicken anaemia in four broiler chicken flocks affected chicks which were all the progeny of the same parent flock. Three of the flocks were reared on farms in the south-east of England and in these flocks clinical disease did not occur in other chicks of the same age. The fourth flock was reared in a positive-pressure isolator and clinical disease appeared at 10 days of age. Chicken anaemia agent was isolated from three of the flocks. The clinical signs, post mortem lesions and histopathological changes were similar to those reported in outbreaks of the disease in other countries. The parent flock seroconverted to chicken anaemia agent, as determined by fluorescent antibody tests, during the course of the outbreaks.     

Invoices and farmer interviews for vaccine-exposure measurement in turkey-broiler production

Exposure measurement in pharmaco-epidemiological studies can be based on various sources that do not always concur. However, reliability is an important criterion when selecting the method used to assess exposure and interpreting the results obtained. An analysis based on invoices might be more informative and more accurate to assess vaccines exposure (yes/no) in turkey broiler production than a questionnaire administered to farmers, which is nevertheless more feasible and less time-consuming. We compared the two methods to assess vaccination exposure in 239 turkey broiler flocks reared in 129 farms in 2000–2001. The agreement (crude agreement and kappa) was calculated, and association between discrepancy and farm and flock characteristics was investigated.

Marek's-disease vaccine, Newcastle-disease vaccine, turkey haemorrhagic-enteritis vaccine and turkey-rhinotracheitis vaccine exposures were reported on the questionnaire for 2.1, 27.6, 93.0, and 98.3% of flocks, respectively, and for 2.1, 29.3, 89.4, and 86.6%, of invoices for the flocks studied, respectively. A discrepancy was observed in 24.9% of flocks. A discrepancy was observed more frequently in specialised farms without any other animal production (OR = 3.6; CI = 1.5, 8.9) and when the farmer did not know whether vaccination had been performed in the hatchery (OR = 7.1; CI = 2.6, 19.7).     

Sources of Salmonellae in broiler chickens in Ontario.

Sources of Salmonellae infecting broiler chicken flocks in Ontario were investigated from July, 1975 to April, 1976. Three broiler flocks were investigated on each of four farms which received chicks from a common hatchery. Samples of feed and new litter were preenriched in nonselective broth subcultured to Salmonella-selective enrichment broth and plated on Salmonella-selective differential agar.Samples of used litter, water, culled chicks, insects, mice, wild birds and environmental swabs were not cultured initially in the nonselective broth. Fecal samples from principal and occasional flock attendants were examined for Samonellae. Salmonella infection, as judged by contaminated flock litter was detected in six flocks on two of the farms while the flocks on the other farms remained negative. Salmonellae were isolated from 23 of 412 feed samples (nine serotypes), six of 35 new wood shaving samples (four serotypes), one of 29 pools of culled chick viscera (one serotype) and 44 of 267 used litter samples (14 serotypes). These results indicate that broiler chicken flocks were infected with diverse Salmonellae introduced in day old chicks, pelleted feeds, wood shavings and residual contamination from the preceding flock.     

Footpad dermatitis in broiler chickens in Japan

The prevalence of footpad dermatitis (FPD) in broiler chickens in Japan was investigated. In the first examination at slaughterhouses, lesions were commonly observed on the footpads of a total of 8,985 broiler chickens from 45 flocks on 36 farms. In 3 flocks, all the birds examined had lesions. In the other 42 flocks, the incidence of FPD ranged from 31.9% (81/254) to 99.5% (1/222). The footpad lesions were classified into 4 categories according to the severity of dermatitis as follows; score 0, 1,181 birds (13.1%); score 1, 2,992 birds (33.3%); score 2, 3,000 birds (33.4%); and score 3, 1,812 birds (20.2%). The mean scores of the flocks varied widely from 0.31 to 2.69. Males had higher mean scores than females. No significant differences were found between the mean scores of birds reared in windowless houses and those in open-sided houses. On 4 farms, the investigation was carried out in different seasons, and 3 of them showed higher mean scores in winter than in summer. Next, observation of 2,255 birds from 15 flocks on 5 farms during a 4-week rearing period revealed that FPD was already produced at 7 days of age and worsened with age.     

An Epidemic of Salmonella Infantis Infection in Finnish Broiler Chickens in 1975–76

A large S. infantis infection epidemic in broiler chickens was studied during a period of one year. The outbreak affected three broiler producing companies in Finland. The infection spread to breeding farms according to available data during the summer of 1975. The epidemic still prevailed at the end of the studies on the farms of certain companies.The origin of the infection and the means of its spreading could not be ascertained. Some epidemiological evidence suggesting that a hatchery might have spread the infection was found. Contaminated feed may also have been involved, although the findings do not support feed as the principal vehicle in the epidemic. A complex pattern of transmission is most probable.A microbiological preventive method based on the feeding of a culture of intestinal flora of adult chickens to newly hatched broiler chickens was used on many farms in the study. The feeding of the culture lowered the proportion of infected flocks on the farms and significantly lowered the number of infected birds in those flocks, where the prevention was not complete. kw|Keywords|k]Salmonella infantis; k]infection; k]epidemic; k]broiler chicken     

Risk factors for Marek's disease and mortality in white Leghorns in Norway

A prospective longitudinal field study was conducted in the period from January 1994 to January 1996 to analyse the relationship between some selected risk factors in the growing and laying periods and (1) the flock-level occurrence of Marek’s disease (MD) during the period from 16 to 32 weeks of age and (2) the cumulative mortality during the same period. A total of 171 layer flocks in 102 egg-production farms were included in the statistical analyses.

A logistic regression (with strain of layer and vaccination program against MD as fixed effects) of flock-level MD-status during the first 16 weeks of the laying period was conducted. Of the risk factors investigated, “multi-age management” and “housing system” were significantly associated at the rearing farm, and “number of hens in each cage” at the egg-production farm. Flocks kept in single-age facilities had a lower risk of MD than flocks housed in farms with multi-age management. The odds of MD were larger for flocks housed on a litter floor in the rearing farms compared to flocks housed in battery cages. At the egg-production stage, flocks kept in battery cages housing more than three hens were at greater risk of MD than those held in cages for three hens or less.

A weighted least-squares regression (with strain of layer and flock-level MD-status as fixed effects) of cumulative mortality during the period from 16 to 32 weeks of age was also run. The same risk factors (with the same directions of effects) and “size of the rearing farm” were included in the final model of mortality. Chicks reared in medium-sized farms were at higher risk of dying than those coming from either small or large rearing farms. Our results confirm the importance of preventing chicks from being exposed to MD-virus during the rearing period, to reduce the risk of MD-outbreaks (and thereby, mortality losses) during the early stage of the egg-laying period.     

Risk Factors Associated with Salmonella Status of Broiler Flocks Delivered to Grow‐Out Farms

In a prospective field observational study in the southeastern USA, we sampled gastrointestinal (GI) tracts from chicks of 65 broiler flocks delivered to conventional grow‐out farms for rearing. The flocks were hatched at seven broiler hatcheries. The mean within‐flock prevalence of Salmonella‐positive samples was 6.5% and ranged from 0% to 86.7%. Of the 65 flocks studied, 25 (38.5%) had at least one Salmonella‐positive sample. Accounting for confounding variability among the hatcheries and broiler companies, we tested whether the probability of detecting Salmonella in GI tracts of the chicks delivered was associated with certain characteristics of parent breeder flocks; hatchery production volume; hatchery ventilation system; hatchery egg‐room conditions; egg incubation, candling, hatching, eggshell and bird separation, and bird‐processing procedures; management of hatchery‐to‐farm transportation; day of week of hatch; weather conditions during transportation; or season of the hatch. Two risk factor models were adopted. The first model indicated that a greater number of parent flocks, manual separation of eggshell and bird, and a greater amount of fluff and feces on tray liners used during hatchery‐to‐farm transportation at delivery were associated with increased probability of detecting Salmonella in chick GI tracts, whereas a greater number of birds in the delivery vehicle was associated with decreased probability. The second model indicated that broiler flocks hatched on Tuesdays versus either Mondays or Thursdays (with no hatches on Wednesdays, Fridays or week‐ends), increased average hatchability of the eggs from the parent flocks, and greater amounts of fluff and feces on the transport tray liners at delivery were all associated with increased probability of detecting Salmonella in chick GI tracts. The results of this study suggest potential management decisions to lessen Salmonella contamination of broilers supplied by commercial hatcheries and areas for further research.     

Newcastle disease outbreaks in Italy during 2000

Among the consequences of the epidemic of highly pathogenic avian influenza which affected Italy between 1999 and 2000 was an epidemic of Newcastle disease in northern and central Italy. It affected industrially reared poultry, dealer flocks and backyard flocks, with a total of 254 outbreaks notified up to December 31, 2000. Virological investigations yielded virulent isolates of Newcastle disease virus, which produced intracerebral pathogenicity indices ranging from 1.6 to 2.0 and which, on the basis of their monoclonal antibody binding patterns, could be classified as belonging to group C1. The clinical, gross and microscopical findings were typical of Newcastle disease, and different avian species were susceptible to different degrees. Chickens and guinea fowl appeared to be the most susceptible, followed by pheasants, turkeys and ostriches. The epidemiological inquiry highlighted the crucial role of a broiler hatchery in initiating the epidemic, and of dealers in perpetuating it. The control measures imposed by Directive 92/66/EEC are discussed with reference to the outbreaks in backyard flocks.     

Characteristics of two duck farming systems in the Mekong Delta of Viet Nam: stationary flocks and moving flocks, and their potential relevance to the spread of highly pathogenic avian influenza

Ducks are considered to play a major role in the spread of highly pathogenic avian influenza (HPAI) H5N1 in Viet Nam, but detailed information on their management is limited. We distinguished two different systems (1) stationary duck flocks that are not commonly driven to rice fields beyond village boundaries and that are confined overnight on farms and (2) moving duck flocks that are intentionally driven to rice fields beyond village boundaries, that are not returning to home farms for extended periods and that are housed overnight in temporary enclosures in rice paddies. A total of 115 stationary and 22 moving flock farmers were interviewed in 2007 in the Mekong Delta of Viet Nam. Moving duck flocks are larger than stationary flocks, which is indicative of their more commercial production. Moving flock farmers apparently are more aware of HPAI risks than stationary flock farmers, as their flocks are more likely fully vaccinated and have less contact with chickens during scavenging. On the other hand, the spread of HPAI virus between birds might be promoted by moving duck flocks as they repeatedly use transport vehicles and numerous rice paddies for scavenging and are often visited by hatchery owners in the field for purchasing duck eggs. In addition, long distances travelled by moving duck flocks might also result in widespread dissemination of HPAI virus. Further studies are necessary to describe HPAI prevalence and travel patterns of moving duck flocks and to explore the moving duck flock network in detail.     

Causes of mortality in commercial organic layers in Denmark

A longitudinal study investigated the courses of mortality in commercial free-range organic layer flocks in Denmark. In total, 15 organic egg-producing flocks from 11 farms were randomly selected among 80 farms registered in Denmark. Four farms with confined egg production on deep litter were included for comparison. Flock sizes ranged from 2260 to 5940 layers. The flocks were monitored from introduction to the layer farm until slaughter. Flock mortalities ranged from approximately 2% to 91%, with a mean of 20.8% for organic flocks compared with 7% for confined flocks on deep litter. In total, 4608 layers were submitted for postmortem examination, representing > 40% of all the dead layers in the investigated flocks. Outbreaks of erysipelas (Erysipelothrix rhusiopathiae) and fowl cholera (Pasteurella multocida) were observed in two and three organic flocks, respectively. The mortality rate reached 91% in one organic flock dually affected by erysipelas and fowl cholera. In six organic flocks, outbreaks of blackhead were diagnosed. Concurrent infections of erysipelas and blackhead were diagnosed in one organic flock. Escherichia coli infections in the form of septicemia were identified in all organic flocks. In addition, cannibalism and constipation contributed significantly to the mortality in some organic flocks. In the confined deep litter flocks, E. coli infection, constipation, and cannibalism represented the most common causes of mortality.     

Risk factors for foot-pad dermatitis in chicken and turkey broilers in France

A prospective cohort study was conducted in the Brittany region to identify the risk factors related to foot-pad dermatitis (considered an indicator of animal well-being) in chicken and turkey broilers reared under commercial conditions. Factors related to the shed, equipment, litter management and stocking density were recorded; the dependent variable was the prevalence of lesions observed on the slaughterhouse chain. Lesions were scored from 0 (no lesion) to 3 (severe lesion). Our survey lasted from May 1999 to October 2000. Fifty flocks of chicken broilers (15 farms), 27 flocks of female turkey broilers (21 farms) and 41 flocks of male turkey broilers (27 farms) were surveyed. In chicken broilers, 10% of flocks were of high quality (80% of birds with score 0) and this was related to the use of concrete floors with a thin layer of wood shavings. In turkey broilers, 48% of female and 46% of male flocks were of bad quality (>10% of birds with score 3). A poor fan ventilation system (<150 m³/h/kg) was a significant risk factor. Turkey flocks of high quality were not observed. Stocking density had no influence on the prevalence of foot-pad dermatitis. We concluded that it is possible under high commercial stocking densities to have flocks with a low prevalence of foot-pad dermatitis in chicken broilers, whereas it is not in turkey broilers. Hence in chicken broilers, implementing a monitoring system based on the observation of foot-pad dermatitis prevalence at slaughter appears to be more appropriate than to legislate stocking density. In turkey broilers, it would probably be necessary either to reduce the stocking density drastically or to investigate new systems of floor drainage.     

The role of backyard poultry flocks in the epidemic of highly pathogenic avian influenza virus (H7N7) in the Netherlands in 2003

In recent years, outbreaks of highly pathogenic avian influenza (HPAI) viruses have caused the death of millions of poultry and of more than 200 humans worldwide. A proper understanding of the transmission dynamics and risk factors for epidemic spread of these viruses is key to devising effective control strategies. The aim of this study was to quantify the epidemiological contributions of backyard flocks using data from the H7N7 HPAI epidemic in the Netherlands in 2003. A dataset was constructed in which flocks in the affected area were classified as susceptible (S), infected but not yet infectious (E), infectious (I), and removed (R). The analyses were based on a two-type SEIR epidemic model, with the two types representing commercial poultry farms and backyard poultry flocks. The analyses were aimed at estimation of the susceptibility (g) and infectiousness (f) of backyard flocks relative to commercial farms. The results show that backyard flocks were considerably less susceptible to infection than commercial farms (), while estimates of the relative infectiousness of backyard flocks varied widely (). Our results indicate that, from an epidemiological perspective, backyard flocks played a marginal role in the outbreak of highly pathogenic avian influenza in the Netherlands in 2003.     

Influence of production system on the rate of onset of Campylobacter colonization in chicken flocks reared extensively in the United Kingdom

1. Because thermophilic Campylobacter spp. are common in chicken flocks reared extensively, cross-sectional and longitudinal studies were carried out on organic and free-range farms to determine the onset of colonisation (lag phase) and likely sources of flock infection. 2. For 14 organic and 14 free range flocks, there was a difference in lag phases, with the former being colonized at a mean of 14·1 d in comparison with 31·6 d for the latter. Whereas most free-range flocks became colonized when released on to pasture, those reared organically were usually colonized at the housed brooding stage. 3. Further study of organic flocks on three farms over 7 successive crop cycles confirmed that colonisation was strongly influenced by the prevailing husbandry conditions and was not a consequence of the length of the rearing period. 4. Molecular epidemiological investigations on a farm showing the shortest lag phase, using PFGE typing with two different restriction enzymes (SmaI and KpnI) and flaA SVR sequence typing, revealed that potential sources of colonisation for organic chickens were already present on the farm at the time of chick placement. Such sources included the ante area of the brooding house, surrounding pasture and other livestock being kept on the farm. 5. Overall, the study demonstrated that, under UK conditions, the prevalence of colonisation was greater in extensive flocks (95-100%) than it was for conventional broilers (55%), similar to the situation in other countries, but all three management systems showed comparable levels of caecal carriage in positive birds (log(10)/g 6·2-6·7).     

Incidence of Clostridium perfringens in broiler chickens and their environment during production and processing.

During a calendar year, a study was conducted involving 16 broiler flocks on four different farms, two farms belonging to each of two major U.S. poultry integrators. As determined by the detection of Clostridium perfringens in fecal or cecal samples, 15 (94%) of the flocks became positive for this bacterial enteropathogen, and only one remained negative throughout the 6-to-8-wk rearing period. Paper pads beneath chicks that were transported from the hatchery to the rearing house were contaminated with C. perfringens in 15 (94%) of the flocks. When sampled biweekly through grow out, 13 of the flocks were C. perfringens positive at 2 wk of age. These results suggest that colonization of the intestinal tract of broilers by C. perfringens is an early event. Of the environmental samples, all but feed in the hopper were contaminated before placement for at least one of the rearing periods. All sample types were contaminated at some point during the 6-to-8-wk grow-out period. Of the on-farm environmental samples, the highest incidences (percentage positive) of C. perfringens were detected in wall swabs (53%), fan swabs (46%), fly strips (43%), dirt outside the house entrance (43%), and swabs of workers' boots (29%). Birds were usually transported to the processing plant in coops that were already contaminated with C. perfringens. In the plant, C. perfringens was isolated more frequently from samples of scald water than from those of chill water. Clostridium perfringens was recovered from broiler carcasses after chilling in 13 (81%) of the 16 flocks. The proportion of C. perfringens-positive carcasses for the contaminated flocks ranged from 8% to 68% with a mean of 30%.     

Comparative investigation of prevalence and antimicrobial resistance of Salmonella between pasture and conventionally reared poultry

The objective of this study was to compare Salmonella prevalence and antimicrobial resistance between pasture and conventional poultry farms. We collected the first Salmonella prevalence and antimicrobial resistance data on pasture poultry farms. Fecal droppings were collected from 31 farms from Wisconsin (nine farms from each production type) and the Southeast (North Carolina, Virginia, and South Carolina; five conventional and 10 pasture poultry farms) in a 1-yr period. The specimens were cultured for Salmonella and tested for resistance to 12 antimicrobials. A univariate analysis was conducted to determine the significant differences in prevalence and resistance. At the farm level, no significant difference in Salmonella prevalence was found on 33% pasture and 47% conventional poultry farms (P= 0.4928). On an individual specimen level, flocks reared conventionally had higher prevalence than in pasture (P < 0.0001). Of all the isolates found to have resistance, 80% were from the Southeast. Of all the pasture isolates tested, 5% (8 of 162) were resistant to ceftriaxone, which is higher than previously reported from any production setting. None of the isolates from conventional flocks showed resistance to ceftriaxone. Multidrug resistance (resistance to three or more classes of antimicrobials) was found in 69% of the isolates from conventional farms and 11% on pasture farms in the Southeast (P < 0.0001), with the predominant resistance type of AmCSSuTeAx (ampicillin, chloramphenicol, streptomycin, sulfasoxazole, tetracycline, amoxicillin/clavulanic acid; 62%). About 5% of the pasture isolates from the Southeast showed the AmAxCFCRO (ampicillin, amoxicillin/clavulanic acid, cephalothin, ceftriaxone) multidrug resistance pattern. None of the isolates from Wisconsin were found to be multidrug resistant.     

Analysis of risk factors for the occurrence of feather pecking in laying hen growers

1. Potential risk factors for the occurrence of feather pecking in laying hen growers raised under commercial conditions were investigated on Swiss farms with more than 500 rearing places. On-farm interviews were conducted on a sample of 64 flocks which represented 42.6% of all farms concerned. 2. All variables considered were dichotomised and their univariate correlation with the occurrence of feather pecking was tested for significance at P <0.20 using chi2 tests. Logistic regression with backward elimination was then used with the significant variables to identify the potentially most important factors influencing feather pecking. These variables included stocking density, light intensity, intensity of care, access to elevated perches, access to a roofed and littered outdoor area ('bad weather run'), time of access to the feeding facilities of the housing system, stocking density in the restricted area at the beginning of the rearing period, additional open feeding areas in the beginning and air quality. 3. The final model contained stocking density and access to elevated perches as significant factors (P<0.05). Flocks kept in high density (> or = 10 birds per m2) and with no access to elevated perches were 6.4 (95% Confidence interval 1.7 to 24.2) and 4.0 (95% Confidence interval 1.2 to 12.9) times more likely to be affected by feather pecking, respectively. 4. The study identified 2 risk factors for the occurrence of feather pecking in flocks of laying hen growers reared under commercial conditions. It is concluded that in order to reduce feather pecking chicks should be reared at low density and with access to elevated perches.     

Akabane disease in sheep

Perinatal lamb mortality, associated with malformations of the CNS due to Akabane viral infection, occurred in 4 of 9 flocks of ewes lambing on 3 farms between 26 May and 14 November, 1976. Cases were restricted to ewes conceiving prior to the second week of March and lambing between 26 May and 19 July. As judged by seroconversion in sentinel flocks on 2 of the farms, field infection with Akabane virus occurred mainly between mid-February and mid-April. Malformations of the CNS occurred in 42.5%, 51.2%, 100% and 31.0% of the dead lambs examined in the affected flocks respectively. Prevalence in the 4 affected flocks, expressed as the proportion of ewes lambing which delivered at least one malformed foetus, was 6.1%, 8.4%, 88.9% and 5.7% respectively. Lamb mortality due to malformations of the CNS was 7.1%, 5.5%, 92.3% and 5.7% of lambs born. Age-specific prevalence was calculated for 3 of the 4 flocks and 2-year-old ewes accounted for 71.4% and 76.9% of total cases respectively in 2 flocks, whereas in one flock malformations occurred at equivalent frequencies throughout several older age groups. Birthweights of affected lambs were usually significantly lighter than those of unaffected lambs of similar sex and birth-type, and their mean duration of gestation was slightly, and significantly, prolonged. Micrencephaly (88.1% of cases) and hydrocephalus (68.7% of cases) were the outstanding pathological features of the malformations with hydranencephaly, microgyria, porencephaly and attenuation of the spinal cord occurring at much lower frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Performance comparison between the use and nonuse of an enteric health medication program across five consecutive commercial broiler flocks

A study was conducted to examine broiler performance and carcass yield across 5 consecutive commercial broiler flocks after the removal of roxarsone (ROX) and growth-promoting antibiotics (GPA) from the feed. Over a 1-yr period, approximately 552,000 broilers were reared in 4 solid-walled, tunnel-ventilated houses, divided into 2 paired-house facilities, and were assigned 1 of 2 dietary treatments. The treated group received basal diets containing salinomycin, ROX, and GPA, whereas the control group received the same diets without ROX and GPA. Average BW were recorded for 200 sample birds/treatment per flock at 18, 35, and 48 d of age. Average BW, feed conversion, adjusted feed conversion, livability, and condemnation were calculated at the completion of each flock. Coccidiosis lesion scores of 10 birds per treatment were recorded at 14, 21, 28, 35, and 42 d of age. Before birds were transferred to a commercial processing plant, 280 birds/flock were randomly selected, weighed, and tagged for carcass yield analysis. Livability was significantly negatively affected by the removal of ROX and GPA. Coccidiosis lesion scores were not affected by the treatments. Tender yields showed significant improvement, whereas all other cuts were not affected by removal of ROX and GPA.     

Investigations of the Distribution and Persistence of Salmonella and Ciprofloxacin‐Resistant Escherichia coli in Turkey Hatcheries in the UK

This study aimed at gaining information on the presence of Salmonella in UK turkey hatcheries and possible epidemiological links between breeding farms, hatcheries and finishing farms. The presence of ciprofloxacin‐resistant E. coli in hatchery samples, as well as in faecal samples from farms, and trends in occurrence of resistance were also investigated. Over a 2 year‐period, four British turkey hatcheries were visited and intensively sampled for the presence of Salmonella and ciprofloxacin‐resistant E. coli. In two hatcheries, a link could be demonstrated between the presence of certain Salmonella serovars in the hatcheries and on breeding and finishing farms. Within the hatcheries, serovars linked to breeding farms were found more frequently in the poult processing and dispatch areas, whereas serovars identified as ‘resident hatchery contaminants’ were predominantly found inside the hatcher cabinets. Ciprofloxacin‐resistant isolates of S. Senftenberg were identified in one hatchery, which coincided with enrofloxacin treatment of some of the breeding flocks. Ciprofloxacin‐resistant E. coli was found in two hatcheries, and the majority of these isolates showed multidrug resistance.     

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.