The potential of the transect method for early detection of welfare problems in broiler chickens

The Aviary Transect - A practical welfare assessment tool to improve the management of cage-free laying hens

The Aviary Transect (AT) is a method for assessing welfare in cage-free laying hen flocks, and comprises standardized walks along each aisle screening the flock for selected welfare indicators: feather loss (FL) on head, back, breast, and tail, wounds on head, back, tail, and feet, dirty plumage, enlarged crop, sickness, and birds found dead. The method is quick (20 min for a flock of 7,500 hens), has good interobserver agreement and shows positive correlations with individual bird sampling methods. However, it is less clear whether AT can be used to detect differences in flock health and welfare related to housing and management. The aim of this study was to evaluate how AT findings varied in relation to 23 selected housing, management, environmental, and production factors. The study was conducted on 33 commercial nonbeak-trimmed, white-feathered layer flocks of similar age (70-76 wk) kept in multitiered aviaries in Norway. The most prevalent findings across flocks were feather loss on the back (mean 0.97% of flock) and breast (0.94%) followed by feather loss on the head (0.45%) and tail (0.36%) with differences in feather pecking damage according to the hybrid used (P < 0.05). Better litter quality was associated with a lower prevalence of feather loss on the head and breast (P < 0.05), and addition of fresh litter during the production cycle resulted in fewer birds with feather loss on the head (P < 0.05) and tail (P < 0.001). Lower dust levels were linked to a lower prevalence of feather loss on the head, back, and breast (P < 0.05), and when access to the floor area underneath the aviary was provided at an earlier stage of production, fewer birds had wounds (P < 0.001), but more birds were observed with an enlarged crop (P < 0.05) and found dead (P < 0.05). In conclusion, findings from AT showed that results of the assessment varied according to housing conditions. These results support the validity of AT as a relevant welfare assessment tool for evaluating cage-free management practices.

Welfare of broilers on farm

This Scientific Opinion considers the welfare of domestic fowl (Gallus gallus) related to the production of meat (broilers) and includes the keeping of day-old chicks, broiler breeders, and broiler chickens. Currently used husbandry systems in the EU are described. Overall, 19 highly relevant welfare consequences (WCs) were identified based on severity, duration and frequency of occurrence: 'bone lesions', 'cold stress', 'gastro-enteric disorders', 'group stress', 'handling stress', 'heat stress', 'isolation stress', 'inability to perform comfort behaviour', 'inability to perform exploratory or foraging behaviour', 'inability to avoid unwanted sexual behaviour', 'locomotory disorders', 'prolonged hunger', 'prolonged thirst', 'predation stress', 'restriction of movement', 'resting problems', 'sensory under- and overstimulation', 'soft tissue and integument damage' and 'umbilical disorders'. These WCs and their animal-based measures (ABMs) that can identify them are described in detail. A variety of hazards related to the different husbandry systems were identified as well as ABMs for assessing the different WCs. Measures to prevent or correct the hazards and/or mitigate each of the WCs are listed. Recommendations are provided on quantitative or qualitative criteria to answer specific questions on the welfare of broilers and related to genetic selection, temperature, feed and water restriction, use of cages, light, air quality and mutilations in breeders such as beak trimming, de-toeing and comb dubbing. In addition, minimal requirements (e.g. stocking density, group size, nests, provision of litter, perches and platforms, drinkers and feeders, of covered veranda and outdoor range) for an enclosure for keeping broiler chickens (fast-growing, slower-growing and broiler breeders) are recommended. Finally, 'total mortality', 'wounds', 'carcass condemnation' and 'footpad dermatitis' are proposed as indicators for monitoring at slaughter the welfare of broilers on-farm.

Differences and variation in welfare performance of broiler flocks in three production systems

There is a trend toward broiler production systems with higher welfare requirements, that use slower growing broiler strains, apply a reduced stocking density and provide environmental enrichment. Although these separate factors each contribute to increased broiler welfare, there is little information on their combined effect on broiler welfare under commercial conditions, and on the variation in welfare performance of flocks within production systems. The aim of this study was to compare the welfare performance and the between-flock variation in welfare of 3 Dutch commercial broiler production systems differing in welfare requirements: Conventional (C), Dutch Retail Broiler (DRB) and Better Life one star (BLS). We applied a welfare assessment method based on the Welfare Quality broiler assessment protocol, in which we used 5 animal-based welfare measures collected by slaughterhouses and hatcheries (mortality, footpad dermatitis, hock burn, breast irritation, scratches), and 3 resource- or management-based measures (stocking density, early feeding, environmental enrichment). Data were collected for at least 1889 flocks per production system over a 2-year period. To compare the different measures and to generate an overall flock welfare score, we calculated a score on a scale from 0 to 100 (bad-good) for each measure based on expert opinion. The overall flock score was the sum of the scores of the different welfare measures. The results showed that with increasing welfare requirements, a higher total welfare score was found across production systems (BLS > DRB > C; P < 0.0001). Regarding individual measures, C generally had lower (worse) scores than BLS and DRB (P < 0.05), except for scratches where C had highest (best) score (P < 0.001). Both welfare measure scores and the total welfare score of flocks showed large variation within and overlap between systems, and the latter especially when only the animal-based measures were included in the total flock score. Total flock score ranges including animal-based measures only were: 112.1 to 488.3 for C, 113.0 to 486.9 for DRB, 151.3 to 490.0 for BLS (on a scale from 0 [bad]–500 [good]), with median values of 330.8 for C, 370.9 for DRB, and 396.1 for BLS respectively. This indicates that factors such as farm management and day-old chick quality can have a major effect on the welfare performance of a flock and that there is room for welfare improvement in all production systems.

Animal Welfare Assessment: Quantifying Differences Among Commercial Medium and Fast Growth Broiler Flocks

A combined welfare assessment protocol, including indicators from the Welfare Quality® and AWIN® EU funded projects, was tested on commercial fast and medium growth commercial broiler flocks to determine differences in their assessments as measured with the used of animal welfare indicators. Ten commercial fast (Ross 308, Cobb 500, or a mix of both) and 10 medium growth (Hubbard JA × Ross 308), mixed sex commercial flocks were assessed at 32 and 48 days of age, respectively. Two observers simultaneously collected data on each flock. Observations included transect walks on central and wall areas to assess the AWIN® welfare indicators, bedding quality, environmental parameters and positive behaviors, all of them collected with the i-WatchBroiler app. According to the WQ protocol, welfare assessment indicators including the human avoidance tests, gait score, body weight and hock burns were also measured on each flock. Novel object tests were also carried out. The results of the study show that fast growth flocks had a higher incidence of welfare issues shown by the higher percentage of immobile, lame, sick, featherless, and tail wounded birds. Positive behaviors such as play fighting, wing flapping and running were more frequently observed in medium growth flocks on central locations, while fast growth flocks had a more limited expression of such behaviors. Fast growth flocks also had worse gait scores. Medium growth flocks expressed a different response to behavioral tests depending on the house location, likely attributable to their better mobility and welfare state, and also to the smaller stocking densities at which they were housed, while on the other hand the behavior of fast growth broilers during tests was similar regardless house location, being likely affected by mobility problems and the higher stocking density specific to their management. These results provide quantitative evidences on the differences in animal welfare assessment outcomes in fast and medium growth broilers. Nevertheless, results also suggest that some of the test responses were associated with the physical state and movement ability of the birds and house location that limit their response capacity. Such limitations should be considered when interpreting animal welfare assessment outcomes. These results add to previously published scientific evidences showing the potential of the method and app technology for practical on-farm broiler welfare assessment, including positive indicators, with farmers, technical personnel, certification bodies or scientist as potential end-users.

The Relationships between Damaging Behaviours and Health in Laying Hens

Since the ban in January 2012 of conventional cages for egg production in the European Union (Council Directive 1999/74/EC), alternative systems such as floor, aviary, free-range, and organic systems have become increasingly common, reaching 50% of housing for hens in 2019. Despite the many advantages associated with non-cage systems, the shift to a housing system where laying hens are kept in larger groups and more complex environments has given rise to new challenges related to management, health, and welfare. This review examines the close relationships between damaging behaviours and health in modern husbandry systems for laying hens. These new housing conditions increase social interactions between animals. In cases of suboptimal rearing and/or housing and management conditions, damaging behaviour or infectious diseases are likely to spread to the whole flock. Additionally, health issues, and therefore stimulation of the immune system, may lead to the development of damaging behaviours, which in turn may result in impaired body conditions, leading to health and welfare issues. This raises the need to monitor both behaviour and health of laying hens in order to intervene as quickly as possible to preserve both the welfare and health of the animals.

Developing a novel welfare assessment tool for loose-housed laying hens - the Aviary Transect method

This study compared welfare assessment results in aviary flocks using 3 approaches: 1) A novel Aviary Transect method, 2) AssureWel, and 3) the Norwegian farm advisors' NorWel method. The Aviary Transect time requirement, interobserver reliability, and within- and across-house sensitivity to detect welfare indicators were also evaluated. The study was conducted on 6 randomly chosen commercial white-strain layer flocks of similar age and flock size, kept in multitiered aviaries. The Aviary Transect method comprised standardized walks along each aisle while screening the whole flock for 12 welfare indicators: feather loss (FL) on head, back, breast, and tail, wounds on head, back, tail, and feet, dirty birds, enlarged crop, sick birds, and dead birds. AssureWel involved scoring FL on head and back, and dirtiness of 50 random birds, and flock-level evaluation of beak trimming, antagonistic behavior, flightiness, birds needing further care, and mortality. NorWel involved scoring 8 welfare indicators on 50 random birds: FL on head, back, breast, and tail, dirtiness, and wounds on head, back, and tail. The AssureWel detected flock differences in both minor and major FL on the back (P < 0.01) as well as somewhat dirty birds (P < 0.01). The NorWel method detected flock differences in both minor and major FL on the head (P < 0.01), back (P < 0.001), breast (P < 0.001), and tail (P < 0.001) and somewhat (score 1) dirty birds (P < 0.05). The Aviary Transect method detected flock differences in FL on head, back, breast, and tail (all P < 0.001), dirty birds (P < 0.05) and enlarged crop (P < 0.001). More birds with FL on breast, and more dirty birds, were found in wall vs. central transects (P < 0.05). There was good interobserver agreement, except for dirty birds (P < 0.01), and positive correlations (P < 0.05) were identified between the Aviary Transect method and the other sampling methods for FL on head and back, and dirtiness. The three methods took similar time to complete (about 20 min/flock). In conclusion, all 3 methods detected significant differences in welfare indicator prevalence between flocks. The new Aviary Transect method provides egg producers with an efficient and sensitive whole-flock assessment of hen welfare status in multitiered aviaries.

Review of litter turning during a grow-out as a litter management practice to achieve dry and friable litter in poultry production

Maintaining dry litter that chickens can “work” is a key objective for successful meat chicken production as it reduces the likelihood of health and welfare issues by breaking down and working excreta and contributing to the water evaporation process. Litter turning is a practice that may help reduce moisture content within the litter by accelerating the drying process when it is combined with effective ventilation. However, information and research about the practice and the effects it could have on the health and well-being of meat chickens (broilers) are minimal. A recent survey of Australian meat chicken growers reiterated the concerns they have about its impact on chicken well-being, but it also demonstrated how growers thought it could enhance the effectiveness of their operation. The aim of this review paper is to identity information relevant to litter turning and the potential effects of this practice on litter quality, ammonia emissions, litter moisture, and animal welfare. This review demonstrates the need for additional research to validate perceptions and address potential concerns and impacts that this practice may have on broiler production. Closing this knowledge gap will improve litter turning practices leading to safer and more consistent outcomes.

Associations between animal-based measures at 11 wk and slaughter data at 20 wk in turkey toms (Meleagris gallopavo)

To monitor animal welfare on a commercial scale, systematic collection and evaluation of slaughterhouse data is the most feasible method. However, we need to know whether slaughterhouse data retrospectively and reliably reflect information about the birds' welfare on-farm. The aim of this study was therefore to investigate associations between animal-based welfare measures in flocks of turkey toms at 11 wk of age recorded with the transect walk and slaughter data at 20 wk of age. A total of 20 commercial flocks of turkey toms were visited, where an observer walked the transects in a random order and recorded the total number of birds per transect that were immobile, lame, with visible head, tail, or wing wounds, small, featherless, dirty, sick, terminal, or dead. Slaughterhouse data were provided for each flock. Univariate and multivariate linear regression models were used to investigate the associations between on-farm and slaughterhouse measures. Increased prevalence of immobile toms at week 11 resulted in more birds rejected at slaughter owing to leg issues (P = 0.02) and airsacculitis (P < 0.001). More lame birds on-farm were associated with an overall higher rejection rate at slaughter (P < 0.001). Flocks with more featherless birds had significantly more birds being rejected at slaughter owing to skin issues (P = 0.02). More dirty birds at week 11 resulted in more birds being rejected owing to airsacculitis at slaughter (P < 0.001). A higher mortality on-farm was associated with more birds rejected for being too small (P = 0.04). In conclusion, significant associations between animal-based measures of turkey toms as assessed by the transect walk method on-farm at 11 wk and slaughter data at 20 wk were identified.

The value of a retrospective analysis of slaughter records for the welfare of broiler chickens

The effects of transport risk factors on deaths on arrival (DOAs; %) and carcass rejections (%) on broiler chickens transported to a slaughterhouse in Southern Spain were assessed using information routinely collected at the slaughterhouse. A total of 2,284 flocks and 10,198,663 broiler chickens, transported in 2,103 commercial transports from 217 different farms to a single slaughterhouse, were studied using the information of veterinary service and slaughter records. Studied risk factors were transport condition at arrival score (good/bad) and plumage condition score (good/bad) at arrival at the slaughterhouse, mixing loads (yes/no), transport duration (min), and season of the year (spring/summer/autumn/winter). Generalized linear mixed models were used to determine the effects of risk factors and their interactions on DOA and carcass rejections. The interactive nature of risk factors affecting both variables was revealed. Mixing loads interacted with transport duration (P < 0.0001), amplifying the negative consequences of long transports on DOA. Mixing loads also interacted with transport conditions at arrival (P = 0.0005), with the impact of bad transport conditions at arrival being particularly negative in the case of mixed loads. These facts raise questions about the suitability of mixing loads both from the animal welfare and economic standpoints. Transport duration interacted with season (P = 0.0003), with the detrimental effect of long distances on DOA being particularly evident during summer and winter, which highlights the need for alternative management measures when hot or cold temperatures are foreseen during transport. Long transports also increased carcass rejections (P < 0.0001). Mixing loads and bad plumage condition exacerbated the overall, detrimental effect of autumn transports on DOA (P = 0.0084 and P = 0.0009, respectively) with respect to summer transports. Similar results were obtained for the interactions between mixing loads and transport season (P = 0.0043) and transport conditions at arrival and transport season (P = 0.0014) on carcass rejections. Overall, results highlight the value of slaughter records to produce information useful to reduce the impact of transport risk factors, improve broiler chicken welfare, and improve slaughterhouse economic results.

Associations between on-farm welfare measures and slaughterhouse data in commercial flocks of turkey hens (Meleagris gallopavo)

There is a growing demand for documentation of animal welfare in meat production industry. Research on turkey welfare has mainly focused on toms at the end of production cycle, and information on the relationship between on-farm welfare and slaughterhouse recordings for turkey hens is currently lacking. The aim of this study was to investigate the relationship between routinely collected slaughterhouse data from turkey hens and their on-farm welfare measured by transect walks, to identify potential retrospective welfare indicators. The study was conducted between November 2017 and March 2018 in 20 commercial turkey flocks in Norway. On-farm welfare was evaluated using the transect walk method when the turkey hens were 11 wk old, recording the number of birds that were immobile, lame, small, featherless, dirty, sick, terminal, or dead and had visible head, tail, or wing wounds. Slaughterhouse data was provided for each flock. Univariate and multivariate linear regression models were used to investigate the associations between the variables. The results showed significant associations between several measures on farm and at slaughter. Flocks with more lameness on farm had more birds rejected at the slaughterhouse owing to leg and joint issues (P = 0.03, r = 1.01). Featherlessness and dirtiness on farm were positively associated with airsacculitis (P = 0.005; r = 0.42 and P = 0.0008; r = 0.57, respectively). The results suggest that slaughterhouse registrations may provide both practical and feasible retrospective information on the welfare of turkey hens that potentially could be implemented in future welfare assessment schemes. Further studies are needed to investigate the causal factors behind the identified relationships.

On-farm welfare assessment of commercial Pekin ducks: a comparison of methods

Although a number of welfare assessment methods have been developed for poultry, none have been evaluated for use in commercial duck farms. The primary objective of the study was to evaluate the inter-rater reliability and relative accuracy of 4 duck welfare assessment strategies. Over 2 experiments, 12 flocks of commercial meat ducks (5,850 to 6,300 ducks/flock) aged 30 to 34 D were evaluated. During experiment 1, six flocks were evaluated using 2 welfare assessment methods: transect walks (TW) and catch-and-inspect (CAI). During TW, 2 observers walked predetermined transects along the length of the house and recorded the number of ducks per transect that were featherless, were dirty, were lethargic, had bloody feathers, had infected eyes, and/or had plugged nostrils or were found dead. During CAI, a total of 150 ducks per flock were corralled and individually evaluated. The same welfare indicators were assessed using both methods. During experiment 2, six flocks were initially evaluated using CAI, TW, and a distance evaluation (DE; a total of 50 ducks per flock evaluated from a walking distance) and then reassessed within 24 h during the loadout (LO) process. Data were analyzed in SAS (version 9.4) to determine the observer and method effects on the incidence of welfare indicators. Interobserver reliability was high (P > 0.05) across methods for most welfare indicators. The assessment method affected the measured outcome variables in both experiments (P < 0.05). CAI resulted in higher estimated incidences of most welfare indicators than TW (experiment 1 and 2) and LO (experiment 2). DE yielded intermediate results compared with other methods (experiment 2). Results obtained using TW and LO were most similar, the only difference being the number of dead birds observed using each method (P < 0.0001). The average time required for CAI, TW, DE, and LO was 2.40 ± 0.004, 1.12 ± 0.02, 1.54 ± 0.001, 3.56 ± 0.006 h, respectively. Bootstrapping analyses showed that the observed welfare indicator prevalence estimates were affected by the number of transects (TW) and number of birds (CAI) sampled.

Broiler Chickens On-Farm Welfare Assessment: Estimating the Robustness of the Transect Sampling Method

Assessing commercial broiler chickens' welfare usually comes at the cost of reduced precision due to the large flock sizes and required time commitments. The transect method for on-farm welfare assessment is conducted by walking within delimited paths between feeder and drinker lines within the commercial house, referred to as transects. This non-invasive method is conducted by detecting birds with signs of impaired welfare indicators, which include leg problems, sickness, body wounds, and feather dirtiness. The transect method has been validated for commercial turkey flocks but not for broiler chickens due to the large flock sizes. The aim of this study was to evaluate the robustness of the transect method in broiler chicken flocks through a capture-recapture approach of a known subpopulation of 80 birds. Groups of 10 chickens were captured and individually marked in eight locations of the house. Two observers collected the number and position of the detected marked birds while walking along non-adjacent transects (four samplings/house/day) during the two following days. Detection and repetition rates per house, and within transects, were calculated, as well as the effects of flock density, transect number/house (six vs. eight), and sampling time (morning vs. afternoon). The number of traveled transects was calculated for birds detected more than once, and the population random distribution was tested by comparing the number of observed and expected birds/transect. Results showed more than 64% of detection rate with a repetition rate/house sampling of 24% and per transect of 1.66%. Higher repetition rates in six-transect houses and during morning samplings were detected. The number of traveled transects was higher in eight-transect houses and from birds first detected at walls, indicating longer traveled distances in wider houses. In addition, bootstrapping techniques were used to calculate the optimal sampling effort. Our findings indicate that the lowest repetition rates and optimal sampling can be achieved by assessing two transects, being one wall and one central, separated by three transects in between. Such sampling procedure would provide robust results for welfare assessment of commercial broiler chicken flocks.

On-farm broiler chicken welfare assessment using transect sampling reflects environmental inputs and production outcomes

To evaluate the utility of transect sampling for assessing animal welfare in large chicken flocks, we quantified relationships between environmental inputs, welfare problems detected using transect sampling, and production outcomes. We hypothesised that environmental inputs including environmental complexity (i.e. number of environmental enrichment types provided), space allowance, underfloor heating (presence or absence), and photoperiod regimen (18 h continuous vs 16 h intermittent) would correspond to variations in welfare assessment findings, which would predict production outcomes. We conducted on-farm welfare assessment of Norwegian broiler flocks at approximately 28 days of age. We sampled four transects (rows between feeder and drinker lines) per flock to determine litter quality and the proportions of chickens with compromised welfare as indicated by visual signs of walking difficulties, illness, skin wounds and small bird size. Production outcome measures included mortality, reasons for carcass rejection at slaughter, footpad dermatitis, growth rate, feed conversion and an integrated production index. Greater environmental complexity was associated with a reduction in skin wounds and total welfare problems on the farm, lower mortality, fewer rejections due to wounds and underweight birds, and fewer rejections overall. Higher space allowances within levels of environmental complexity were associated with fewer walking difficulties and welfare problems overall, a reduction in rejections due to wounds, and a higher growth rate and production index. Underfloor heating was associated with a reduction in rejections due to leg deformity, and intermittent light was associated with lower illness and skin wound rates on the farm, and lower mortality. Furthermore, fewer welfare problems and better litter quality on the farm were associated with fewer carcass rejections at slaughter. Thus, data from transect sampling varied with environmental inputs and production outcomes, supporting the validity of transect sampling for practical, animal-based on-farm welfare assessment.