Do farming conditions influence brominated flame retardant levels in pig and poultry products?

Brominated flame retardants (BFR) are primarily used as flame retardant additives in insulating materials. These lipophilic compounds can bioaccumulate in animal tissues, leading to human exposure via food ingestion. Although their concentration in food is not yet regulated, several of these products are recognised as persistent organic pollutants; they are thought to act as endocrine disruptors. The present study aimed to characterise the occurrence of two families of BFRs (hexabromocyclododecane (HBCDD) and polybrominated diphenyl ethers (PBDE)) in hen eggs and broiler or pig meat in relation to their rearing environments. Epidemiological studies were carried out on 60 hen egg farms (34 without an open-air range, 26 free-range), 57 broiler farms (27 without an open-air range, 30 free-range) and 42 pig farms without an open-air range in France from 2013 to 2015. For each farm, composite samples from either 12 eggs, five broiler pectoral muscles or three pig tenderloins were obtained. Eight PBDE congeners and three HBCDD stereoisomers were quantified in product fat using gas chromatography-high-resolution mass spectrometry, or high-performance liquid chromatography-tandem mass spectrometry, respectively. The frequencies of PBDE detection were 28% for eggs (median concentration 0.278 ng/g fat), 72% for broiler muscle (0.392 ng/g fat) and 49% for pig muscle (0.403 ng/g fat). At least one HBCDD stereoisomer was detected in 17% of eggs (0.526 ng/g fat), 46% of broiler muscle (0.799 ng/g fat) and 36% of pig muscle (0.616 ng/g fat). Results were similar in concentration to those obtained in French surveillance surveys from 2012 to 2016. Nevertheless, the contamination of free-range eggs and broilers was found to be more frequent than that of conventional ones, suggesting that access to an open-air range could be an additional source of exposure to BFRs for animals. However, the concentration of BFRs in all products remained generally very low. No direct relationship could be established between the occurrence of BFRs in eggs and meat and the characteristics of farm buildings (age, building materials). The potential presence of BFRs in insulating materials is not likely to constitute a significant source of animal exposure as long as the animals do not have direct access to these materials.

Feather pecking in laying hens housed in free-range or furnished-cage systems on French farms.

1. Beak trimming is currently used in France to avoid the negative consequences of severe feather pecking (SFP). However, this practice is controversial in terms of animal welfare, and forbidden in some European countries.2. This study aimed to assess the prevalence of SFP in French laying hen farms, to describe how farmers manage this behavioural disorder and to better understand the risk factors involved.3. A study was carried out from April 2015 to June 2016. Visits were paid to 79 flocks kept in furnished cages (FC) and 80 flocks in a free-range (FR) system. All the hens had trimmed beaks and were genotypically brown. The information collected included feather cover, skin damage, beak condition, farm and poultry house characteristics, livestock performance and management.4. The prevalence of SFP in FC flocks was estimated at 32.9% (IC = 95%, [22.5; 43.3]) and the prevalence of cannibalism as 2.5% (IC = 95%, [0.7; 8.8]) at 70 weeks of age. The prevalence of SFP in FR flocks was estimated to be 23.8% (IC = 95%, [14.5; 31.1]) and the prevalence of cannibalism was 8.8% (IC = 95%, [4.3; 17.0]) at 61 weeks of age.5. In FC flocks, SFP was associated with the combination of genotype, type and length of perches, cage area per hen, type of lighting, number of hens per cage and farm location. In FR flocks, feather cover was associated with use of the outdoor run, lighting programme, genotype, farm location and date of house construction.

Exposure to inhalable dust of workers shackling birds frequently exceeds occupational exposure level in abattoirs in Western France.

1. The objectives of this study were to measure the exposure of workers to dust when shackling poultry in abattoirs, and to identify the most effective measures to prevent human exposure to dust. The relationship between respiratory health of workers and their occupational exposure to dust was assessed. 2. Exposure to dust (aerial particles inhaled through the nose and mouth) exceeded the occupational exposure limit (maximum 10 mg/m3 over 8 h) in 65 out of 109 workers from 27 abattoirs, in the context of high levels of ambient aerial dust in small, closed shackling cubicles. Ceiling air ducts for supply of air reduced worker exposure to dust in these buildings. 3. Two-thirds of the 86 workers interviewed reported work-related respiratory symptoms. The self-reported risk of suffering from coughing tended to be associated with the highest exposure to inhalable dust and respiratory dust (aerial particles penetrating up to alveoli) observed in the study. 4. The present study demonstrates that workers may be exposed to considerable amounts of dust when shackling birds before stunning.

Randomized control trial to test the effect of a feed additive on Campylobacter contamination in commercial broiler flocks up to slaughter.

A randomized controlled trial (RCT) was carried to evaluate the effect of a feed additive on Campylobacter contamination of broilers reared in commercial conditions. Twenty-four broiler flocks naturally contaminated with Campylobacter were enrolled in the RCT: 12 were assigned to a control group (C) fed with a conventional finishing feed from 4 weeks of age to slaughter (around 35 days), and the other group of 12 flocks (S) was fed with a finishing feed supplemented with 250 ppm of a patented feed additive (an ion-exchanged clay compound) previously proven to reduce Campylobacter contamination in broiler caeca under experimental conditions. Enumeration of Campylobacter colonies in caeca (8 per flock) was carried out following ISO standards before feed distribution and at slaughter. Before treatment, the caecal Campylobacter load tended to be lower in C flocks (7.1 ± 1.9 log CFU/g, CI95% [6.6-7.5]) than in S flocks (7.7 ± 1.0 log UFC/g, CI95% [7.5-7.9]) (p = .05). At slaughter, the bacterial load was similar in the S (7.7 ± 1.0 log CFU/g, CI95% [7.5-7.9]) and C groups (7.5 ± 1.2 log CFU/g, CI95% [7.2-7.8]) (p = .73). Therefore, the feed additive had no significant effect on the caecal Campylobacter load at slaughter under the tested conditions. The logistical constraints inherent in field trials and the natural variability of Campylobacter contamination in naturally infected broiler flocks make it difficult to reproduce experimental results in in situ farm conditions. RCT testing of an intervention strategy in commercial situation is therefore a key step in evaluating pre-harvest interventions against food-borne pathogens.

A multi-pronged approach to the search for an alternative to formaldehyde as an egg disinfectant without affecting worker health, hatching, or broiler production parameters.

Research was carried out to determine the effectiveness of 4 hatching eggs disinfection processes (i.e., disinfecting products and administration method) using a multi-pronged approach assessing the reduction of microbial eggshell contamination, the effects on worker exposure, hatching results and broiler performance, and, finally, suitability for use in commercial hatcheries. The 4 disinfection processes were: sodium dichlorocyanurate (DC) by thermonebulization, hydrogen peroxide 6% by nebulization (HP6), electrolyzed oxidizing water (EOW) by fogging, and hydrogen peroxide 30% vapor (HP30). In order to meet commercial hatchery conditions, the tested products were applied in an experimental hatchery by aerial disinfection in a dedicated room, not sprayed directly onto the eggs. Compared to the untreated control group, eggshell microbial load was significantly decreased by over 1 log10 cfu per egg in groups DC and HP30. These results were confirmed during a second experiment. In addition, these 2 products comply with legal requirements on worker exposure. Fertility and hatching results were significantly higher in group HP30 than in group DC, with no impact on chick quality and subsequent broiler performance. Under these study conditions, the disinfection process (i.e., administration of the product, contact with the eggs and aeration) lasted 65 min in group DC vs. 135 min in group HP30. When considering commercial hatchery conditions, this difference in application time confers a clear advantage on the DC process. Moreover, the investment required for HP30 is much higher than for DC. Overall, HP30 presented a clear advantage for hatching results whereas DC is a relatively more practical and less expensive disinfection process. To our knowledge, this is the first report on the use of hydrogen peroxide vapor as an egg disinfection process. Further research is needed to confirm the results of this study under commercial hatchery conditions.

Contribution of Meat Inspection to the surveillance of poultry health and welfare in the European Union.

In the European Union, Meat Inspection (MI) aims to protect public health by ensuring that minimal hazardous material enters in the food chain. It also contributes to the detection and monitoring of animal diseases and welfare problems but its utility for animal surveillance has been assessed partially for some diseases only. Using the example of poultry production, we propose a complete assessment of MI as a health surveillance system. MI allows a long-term syndromic surveillance of poultry health but its contribution is lowered by a lack of data standardization, analysis and reporting. In addition, the probability of case detection for 20 diseases and welfare conditions was quantified using a scenario tree modelling approach, with input data based on literature and expert opinion. The sensitivity of MI appeared to be very high to detect most of the conditions studied because MI is performed at batch level and applied to a high number of birds per batch.

Effect of substrate provision on performance and behaviour of laying hens in the pecking and scratching area of furnished cages.

1. An experiment was set up to study the effects of substrate provision on performance and behaviour in the pecking and scratching area (PSA) of non-beak-trimmed hens housed in large furnished cages (60 hens/cage). 2. Three layer hybrids (two brown and one white, ISA-Hendrix Genetics, France) and two substrate conditions (with or without wheat bran automatically distributed on the PSA) were compared in a 3 × 2 experimental design with 12 cages per treatment. 3. Substrate distribution improved laying rate with no impact on the frequency of dirty or cracked eggs. 4. Substrate distribution improved the viability and body integrity of hens, which were not beak-trimmed. 5. Distribution of substrate tended to increase the number of hens in the PSA and enhanced their pecking and scratching behaviours but had a negative impact on the number of dust bath bouts per cage and encouraged dust bathing on the wire floor close to the feeder. 6. The white hens laid more eggs in the nest than the brown birds and used the PSA more for pecking, scratching and dust bathing at the end of the day than the brown hens, underlining the necessity to adapt cage furnishing and rearing management to specific behaviours of each layer genotype.

Aerial dust concentration in cage-housed, floor-housed, and aviary facilities for laying hens.

Agricultural workers, and pig and poultry farmers in particular, are exposed to airborne contaminants including organic dusts, gases, fungi, bacteria, and endotoxins that can have adverse effects on their respiratory health. To date, data comparing the aerial dust concentrations in the different hen-housing systems used by commercial poultry farmers are scarce. An epidemiological study was conducted in commercial housing facilities for laying hens, half of which were housed in a cage system without litter and the remaining half on an on-floor system with litter. The aims were to measure and compare the ambient dust concentrations in the different housing systems and identify any factors in building design and hen management that could influence the dust burden. An average concentration of respirable ambient dusts (≤4 µm) of 0.37 mg/m(3) (95% CI [0.31-0.42]) was measured in the on-floor system, and this value was higher than average values in the cage system {0.13 mg/m(3) (95% CI [0.11-0.14]) P = 0.01}. The highest dust concentration was observed in aviaries (1.19 mg/m(3) [0.80-1.59]). The type of housing and the presence of litter therefore had a preponderant effect on air quality. Dust concentrations in caged buildings were influenced by cage design and rearing practices, whereas litter management, the age of hens, and temperature control were determining factors for dust levels in on-floor houses. This study underlines the need for information and preventive measures to reduce the exposure of poultry workers to bioaerosols, particularly in alternative systems where high levels of ambient dust were observed.

Risk factors for the introduction of avian influenza virus in breeder duck flocks during the first 24 weeks of laying.

A study was carried out in French breeder duck flocks in 2008 and 2009 to identify practices and events related to the introduction of avian influenza viruses (AIVs). The status of flocks was assessed using serological methods for all subtypes of AIV without typing. Flocks managed with both natural mating and artificial insemination were investigated every 4 weeks from the beginning of the laying period up to seroconversion or for a maximum of 6 months. A questionnaire was completed with the farmer during each visit and 20 female ducks were randomly sampled for blood testing. Only flocks that tested seronegative at the first visit were included in the study (n =151 flocks managed with natural mating or artificial insemination). Data were analysed using survival analysis to identify factors influencing the time to seroconversion. Three separate models were constructed: one for the whole sample, one for natural mating flocks, and one for artificial insemination flocks. Factors related to the time to introduction of AIV included the type of production system linked to artificial insemination practices, the neighbourhood, poor disinfection practices, liquid manure management, presence of wildlife, and vehicles entering the building. No clear relationship could be observed in the serological status of male and female ducks in farms keeping male ducks separately from female ducks for artificial insemination. By respecting carefully biosecurity measures, it should be possible to decrease AIV infection of breeder duck flocks.

Plumage condition, body weight, mortality, and zootechnical performances: the effects of linings and litter provision in furnished cages for laying hens.

This experiment was designed to determine the effect of litter provision and lining in nests and pecking and scratching areas on health and zootechnical performances. Research was carried out in furnished cages, each housing 60 beak-trimmed ISA Brown hens. Four different treatments were compared in a factorial arrangement, including 2 different nest linings (artificial turf versus plastic mesh), either used alone or combined with the use of litter (wheat bran) spread over the rubber mat in the pecking and scratching area (PSA). An additional treatment using artificial turf mat in the PSA and nests (as commonly used in commercial flocks) was used to compare the effect of PSA lining in the other treatments. Zootechnical performances (laying rate, egg weight, and feed intake) were unaffected by PSA lining or by nest lining. The use of artificial turf mats in the PSA resulted in less feather loss than rubber mats, especially on breast and cloaca/vent areas. No consequences were observed on BW or mortality. However, the use of plastic mesh in nests was seen to increase mortality in comparison with artificial turf mats, without affecting plumage condition and BW. Although wheat bran provision did not influence feed intake and laying rate, litter provision did result in slightly higher mean egg weight. Moreover, BW tended to be lower when litter was distributed in cages, and neck and breast plumage condition improved. The distribution of litter was not seen to have any effect on mortality. The provision of litter and the lining of the PSA and nests to improve the welfare of caged laying hens have an effect on mortality, plumage quality, and some zootechnical performances. These results show the importance of choosing the most suitable linings and litter to obtain the best possible compromise between the ethological needs of laying hens, zootechnical performance, and animal health.

Cage hygiene, laying location, and egg quality: the effects of linings and litter provision in furnished cages for laying hens.

This study investigates the influence of litter provision and linings used for nests and pecking and scratching areas on cage hygiene, laying location, and egg quality. Research was carried out in furnished cages, each housing 60 beak-trimmed ISA Brown hens. Four different treatments were compared in a factorial arrangement, including 2 different nest linings (artificial turf vs. plastic mesh), either used alone or combined with the use of litter (wheat bran) spread over the rubber mat in the pecking and scratching area (PSA). An additional treatment, using artificial turf mat in the PSA and nests (as commonly used in commercial flocks), was used to compare the effect of PSA lining in the other treatments. We observed laying location, the number of dirty and broken eggs, the microbiological contamination of eggshells according to laying location, and general cage hygiene. The use of nests for laying decreased when they were lined with plastic mesh. Eggs laid outside the nest were of lower quality than those laid inside it, and this was particularly true for eggs laid in the PSA. Although hygiene was low on artificial turf mats, eggs laid on PSA covered with a rubber mat were dirtier and had a higher count of mesophilic bacteria on the eggshell than those laid on PSA covered with an artificial turf mat. Rubber mats in PSA were rapidly destroyed and proved to be unsuitable. The provision of litter had no effect on cage hygiene but substantially increased wear on mats. This study shows nest lining and litter provision methods to be key factors that need to be taken into account to encourage the use of nest boxes for laying, and hence, to ensure good egg quality. Further research into new linings for PSA is needed for the future improvement of egg-laying conditions.

Endotoxin concentration in poultry houses for laying hens kept in cages or in alternative housing systems.

Endotoxins as components of organic dust may have adverse effects on the respiratory health of workers in poultry buildings. The move towards more welfare-friendly housing systems for layers may increase worker exposure to air contaminants due to the use of litter. The endotoxin concentrations in the inhalable fraction of airborne dust (below 100 µm) from cage and alternative system houses (on-floor, free range and aviaries) were compared under both experimental and commercial conditions. The endotoxin concentration was higher in experimental aviaries (median: 565 EU/m³, range: 362-1491 EU/m³) than in cage housing (98 EU/m³ (51-470)). In field conditions, the endotoxin concentration in the air of 13 alternative houses was higher (35 to 3156 EU/m³) than in cage system buildings (n = 8, 78-576 EU/m³). It was correlated to the respirable dust concentration (fraction below 5 µm) and to the temperature inside the hen house but no seasonal variation was observed. The present study emphasises that considerable worker exposure to endotoxins may occur in laying houses, especially in alternative systems.

Furnished cages for laying hens: study of the effects of group size and litter provision on laying location, zootechnical performance and egg quality.

The furnished cage is a new housing system for layers. A current trend in furnished cage design is to increase group size and replace the litter box with a mat provided with litter. An experiment was set up to determine the effects of group size and litter provision on laying performance and egg quality of beak-trimmed ISA Brown hens housed in large furnished cages with more than 12 hens. Six treatments, each of 18 furnished cages (768 cm(2)/hen including nest and litter area) were compared in a 3 × 2 experimental trial: three group sizes (S20 (20 hens per cage), S40 (40) and S60 (60)), with or without feed as litter distributed on the mat of the litter area. The provision of facilities per hen was equal in all treatments. Mortality, laying rate, mean egg weight, feed intake and feed conversion ratio were unaffected by group size over the 53-week laying period, and performance exceeded the ISA production standards. The overall percentage of eggs laid in the nest exceeded 95% except that it was slightly lower in group S20 (92.0% ± 6.4% v. S40: 96.0% ± 3.3% and S60: 96.2% ± 2.7%) leading to a higher proportion of dirty eggs (S20: 1.6% ± 2.2%, S40: 1.4% ± 1.5%, S60: 1.0% ± 1.0%). At 66 to 70 weeks, eggs laid outside the nest had a slightly higher count of mesophilic bacteria on the eggshell (5.0 log CFU/egg ± 0.4) than those laid in the nest (4.8 log CFU/egg ± 0.5) but no difference in contamination was observed between group sizes. Litter provision had no effect on mortality, egg weight or egg quality traits except for a higher proportion of broken eggs in cages with litter (5.3% ± 6.2% v. 4.6% ± 5.7%). Providing hens with feed for litter was associated with a higher laying rate (97.3% ± 3.2% v. 94.8% ± 4.4% at 23 weeks) and an apparent improvement in feed efficiency at the beginning of the laying period (feed conversion ratio based on feed consumption at the trough: 2.18 ± 0.06 with litter v. 2.28 ± 0.09 without litter at 25 weeks). The results of this study showed that a high level of productivity and good egg quality could be obtained in large furnished cages. Further research is needed to assess the impact on hens' welfare and performance of using more economically competitive substrates than feed for litter.

Factors influencing bacterial eggshell contamination in conventional cages, furnished cages and free-range systems for laying hens under commercial conditions.

1. The aim was to assess eggshell contamination in various laying hen-housing systems and to identify factors influencing this contamination. 2. Fifty-eight laying hen farms in France were studied, including 21 flocks housed in conventional cages, 7 in furnished cages and 30 kept on-floor. 3. Sixty eggs per flock were analysed to obtain counts of the total mesophilic flora. Data on equipment and hen management were collected. 4. Mean bacterial count on eggshells tended to be higher in on-floor systems (4.82 +/- 0.51 log CFU/eggshell) than in cage systems (4.57 +/- 0.58 log CFU/eggshell, P = 0.09). 5. Contamination increased with age of the hens, airborne dust concentration, manual packing of the eggs, and packing in plastic rather than in recycled-pulp egg-flats. 6. The effect of the housing system on eggshell contamination, previously described in experimental assays, was confirmed under production conditions.

Evaluation of common cleaning and disinfection programmes in battery cage and on-floor layer houses in France.

1. The aim in this study was to evaluate cleaning and disinfection programmes in battery cage and on-floor layer houses in France. 2. Cleaning and disinfection efficiency was assessed by a visual evaluation of cleaning and a bacteriological monitoring of surface contamination from counts of thermotolerant streptococci on contact agar plates. 3. In battery cage houses, dropping belts, manure conveyors, and house floors remained highly contaminated due to poor cleaning in half of the buildings examined. 4. In on-floor houses, a high standard of cleaning was achieved but errors in the planning of cleaning and disinfection operations sometimes led to a high residual contamination of nest boxes and egg sorting tables.

Diversity of pulsed-field gel electrophoresis profiles of Campylobacter jejuni and Campylobacter coli from broiler chickens in France.

In 2003 to 2004, 26 free-range broilers flocks excreting Campylobacter were studied for identification of Campylobacter species and genotype diversity. Seventeen flocks were sampled at the end of the indoor rearing period and 9 before departure to the slaughterhouse after access to an open area. Out of 513 isolates, 315 were identified as Campylobacter jejuni and 198 as Campylobacter coli. Pulsed-field gel electrophoresis analysis revealed 35 genotypes for C. jejuni and 43 genotypes for C. coli; 38.4% of the isolates were clustered into 16 genetic groups. This kind of poultry production system is characterized by a large number of Campylobacter coli isolates. Flocks sampled during the indoor phase were predominantly contaminated by C. jejuni, whereas those sampled during warm months were predominantly contaminated by C. coli. The Campylobacter population was genetically highly diverse: multiple genotypes were detected in a single flock. Six flocks were each found to harbor a mixture of genotypes; these isolates were genetically closely related and were grouped into clusters of at least 80% genetic similarity. Isolates with genotypes found in different flocks and strains, but sharing the same genetic clusters, were detected in different farms and at different times in the year. Flocks sampled during the indoor rearing period and when farmers use fresh farm-made litter were associated with a small number of clusters. In conclusion, Campylobacter species were genetically highly diverse. Our findings suggest the presence of genomic rearrangements in Campylobacter colonizing the chick intestine and that some Campylobacter strains are adapted to poultry. In addition, the species diversity in the flocks was affected by season and cloistering measures. Litter and exposure to an open area were likely sources of flock Campylobacter contamination.

Bayesian estimation of flock-level sensitivity of detection of Salmonella spp., Enteritidis and Typhimurium according to the sampling procedure in French laying-hen houses.

A study was carried out to estimate the prevalence of flocks infected by Salmonella spp., S. Enteritidis and S. Typhimurium in 521 French laying-hen farms from October 1st 2004 to September 30th 2005 as part of a European Union-wide baseline study to define targets for Salmonella reduction in member states. The sampling scheme prescribed and financed by the European Commission to detect Salmonella in laying-hen flocks was based on 2 dust-samples and 5 faeces-samples per farm. A latent-class Bayesian approach for correlated tests was used to estimate the sensitivity of detection of reduced sampling schemes corresponding to the 16 combinations of 2 dust- and 5 faeces-samples. For each model the full sampling scheme (7 samples) and the reduced protocol were considered as two correlated tests, the biological principle being identical and the reduced protocol being a subset of the full sampling scheme. As the observed apparent prevalence in cage flocks was higher than in other systems (barns, outdoor, or organic) these two sub-populations were considered separately. Bayesian estimation of posterior medians with 95% probability intervals for true prevalence in cage flocks were 0.34 (0.29; 0.39) and 0.13 (0.10; 0.18) for Salmonella spp. and Salmonella Enteritidis+Typhimurium respectively. In alternative flocks posterior medians with 95% probability intervals for true prevalence were 0.09 (0.06; 0.13) and 0.05 (0.03; 0.08) for Salmonella spp. and Salmonella Enteritidis+Typhimurium, respectively. In cage flocks Bayesian estimation of posterior distributions for sensitivity indicated that at least 5 samples, including 2 dust samples were necessary to attain comparable sensitivity levels to the full sampling scheme. In alternative flocks and for Salmonella spp. 6 samples were required to ensure a comparable sensitivity level to the full sampling scheme. Detection sensitivity was improved by increasing the number of dust samples in cage farms and by increasing the total number of samples whatever their type in alternative farms.

Risk factors for Campylobacter spp. colonization in French free-range broiler-chicken flocks at the end of the indoor rearing period.

The aim of this cross-sectional survey was to identify risk factors for Campylobacter spp. colonization in French free-range broiler flocks at the end of the indoor rearing period (between 35 and 42 days old). Seventy-three broiler farms were studied from March 2003 to March 2004 in France. A questionnaire was administered to the farmers and samples of fresh droppings were taken to assess the flocks'Campylobacter status by bacteriology. Campylobacter species were determined by PCR. A logistic regression analysis was used to assess the influence of various factors on flocks'Campylobacter status. 71.2% of the sampled flocks excreted Campylobacter spp. before going out on the range. The risk of a flock being colonized with Campylobacter was increased in the spring/summer period (RR=1.8, p=0.02) and autumn (RR=2.2, p=0.02) compared to winter, on total freedom rearing farms (RR=3.3, p=0.04) in comparison with farms with a fenced run, when the first disinfection of the poultry-house was performed by the farmer (RR=2.4, p=0.04) instead of a hygiene specialist, when rodent control was carried out by a contractor (RR=1.8, p<0.01) and not by the farmer and when the farmer came into the house twice a day as opposed to three time a day or more (RR=1.5, p=0.02). Use of a specific gate for chick placement decreased the risk of a flock being colonized with Campylobacter (RR=0.5, p=0.01) in comparison with using the gate for manual disposure or the door of the change room.