Separating the impact of group size, density, and enclosure size on broiler movement and space use at a decreasing perimeter to area ratio

Comparative Analysis of Broiler Housing Systems: Implications for Production and Wellbeing

This study compares the effects of modern colony cage systems and traditional floor systems on the production and welfare of broiler chickens. Through two trials spanning 35 days each, we evaluated various physiological parameters, including growth performance, bone health, stress responses, and meat quality. Colony cages demonstrated superior thermal regulation and growth performance compared to traditional floor systems, but also exhibited higher frequencies of leg deformity and reduced standing ability. Conversely, the broilers in traditional floor systems experienced heat stress-related challenges, impacting the meat quality. Our findings underscore the need to balance productivity with animal welfare in broiler farming practices. By understanding the distinct impacts of different housing systems, we can work towards improving broiler rearing methods to ensure optimal welfare and production outcomes.

Laying Hens: Why Smothering and Not Surviving?-A Literature Review

The proliferation of rearing systems providing opportunities for birds to engage in natural behaviors can trigger behavioral repertoires that when not manageable compromise animal welfare and the economic viability of the flock. Smothering in laying hens has long been perceived as "natural" or the result of hysteria among birds in the flock. However, the current literature has recognized smothering as an abnormal outcome with the potential to result in significant losses in cage-free poultry systems. Recent studies have specifically aimed to categorize the organization of smothering behavior and highlight its potential causes and consequences. In this study, literature review and bibliographic mapping, drawing on published articles and engagement with poultry farmers through extension and rural technical assistance, were employed. The findings indicate that smothering is a behavior triggered by factors related to the environment in which the laying hens are kept. This study concludes that there is a critical need for more rigorous and detailed research to elucidate the nuances of avian behavioral physiology and assess the impact of production systems on animal welfare and the economic impacts on the flock. This research contributes to a deeper understanding of bird behavior in high-production environments and provides practical insights for the poultry industry.

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.

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.

Effects of cage size on growth performance, blood biochemistry, and antibody response in layer breeder males during rearing stage

This study was conducted to investigate the effects of cage size on growth performance, blood biochemistry, and antibody response in layer breeder males during rearing stage. 575 one-day-old Jinghong layer breeder males were randomly allocated into 3 treatments and reared in 3 cage sizes: large (160 × 160 × 62 cm; LC), medium (120 × 120 × 62 cm; MC), and small (80 × 70 × 62 cm; SC). The stocking density of birds in 3 treatments was kept identical and adjusted every 2 wk, from 45 birds/m2 during the period of 0 to 2 wk of age to 12 birds/m2 during the period of 17 to 18 wk of age. Body weight and shank length were measured every 2 wk, and then the daily weight gain and daily feed intake were calculated. Tibia length and breaking strength were determined at 8 wk of age. Blood parameters including malodiadehyde (MDA), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), alkaline phosphatase (ALP) and corticosterone (CORT), and antibody titers against avian influenza viruses H5N1 (Re-5 strain) and H9N2 (Re-2 strain) and Newcastle disease virus in response to vaccination were determined at 18 wk of age, respectively. Body weight, shank length, and daily weight gain of birds in LC were similar with those in MC, and were greater than those in SC at 18 wk of age (P < 0.05), respectively. No significant difference was found in average daily feed intake among the 3 treatments from 11 to 18 wk of age. Birds in LC and MC had the similar tibia length; however, birds in SC were smaller (P < 0.05). Tibia breaking strength of birds in LC was higher than those in SC (P < 0.05), respectively. Birds in LC showed lower plasma MDA, GSH-Px, SOD, and CORT contents than those in MC and SC (P < 0.05); however, birds in LC exhibited higher levels of serum antibody titers against H5N1 and H9N2 avian influenza viruses as compared with MC and SC (P < 0.05). Consequently, LC and MC were superior to SC and were beneficial for birds' growth and development.

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.

Meta-analysis of the effects of intensive rearing environments on the performance and welfare of broiler chickens

To better understand how relevant intensive systems’ characteristics simultaneously affect the performance and welfare of broiler chickens, a meta-analysis of recent literature was carried out. The study determined the effects of gender, genetics, experimental initial age (EIA, d), stocking density (SD; kg/m²), group size (GS; n), bedding material (yes/no), duration of photoperiod (DP; h), divided scotoperiod (yes/no), feeding phases (1/2/3/>3), environmental control (EC; yes/no), environmental enrichment (yes/no), use of vaccines and other medications (yes/no), experimental duration (d), and relevant 2-way interactions on average daily gain (g/d), average daily feed intake (g/d), FCR (g: g), mortality (%), behavior (%), and gait score (mean value). Predictive equations for response variables were calculated using multiple regression models including a random experiment effect. Among other results, EIA × SD interaction indicated that relatively high SD may improve FCR at older ages, but parallel increased mortality would pose concerns about the actual productive benefits and welfare. Combining large GS and relatively low SD seem to improve performance and decrease flock disturbance. They would also increase leg problems, and so their actual benefits on welfare remain unclear. A gradual increase in FCR seems to occur with longer DP at older EIA (EIA × DP interaction), highlighting the importance of adapting light programs to flock age to optimize performance. The SD × DP and GS × DP interactions predicted increased FCR for longer DP at low SD or large GS, that is, with more effective space available. Longer DP combined with low SD or large GS would overall promote enhanced leg conditions, and therefore welfare. Predictions would not support scotoperiod division from both performance and welfare perspectives. The SD × EC interaction indicated that EC would benefit chicken performance at low SD, although EC would seem to increase leg problems. Our study highlights the complex, interactive nature of production systems’ characteristics on broiler chicken performance and welfare.

A review of the effects of stocking density on turkey behavior, welfare, and productivity

Stocking density, the amount of space available per animal, greatly affects the welfare of commercial turkeys. For example, stocking density has been found to affect behavior such as injurious pecking; production, such as growth rates and feed efficiency; and health-related aspects, such as leg health and the incidence of airsacculitis. Current industry guidelines and standards for turkey space requirements and stocking densities vary, and they are different from those that have been examined scientifically. Scientific research into stocking density effects on turkey behavior, welfare, and productivity have been conducted in experimental settings with flock sizes that are much different from those in the commercial turkey industry. There is currently little information available regarding how much space turkeys require for particular behavioral activities. This paper reviews the current industry guidelines and standards as well as scientific literature pertaining to stocking densities for commercial turkeys.

Ranging Behaviour of Commercial Free-Range Broiler Chickens 1: Factors Related to Flock Variability

Simple Summary

Free-range chicken meat consumption has increased. However, little is known about how meat chickens use the outdoor range. Understanding ranging behaviour could help improve management and shed and range design to ensure optimal ranging opportunities. We tracked 1200 individual broiler chickens in four mixed sex flocks on one commercial farm across two seasons. More chickens accessed the range in summer than winter. Chickens that accessed the range in winter did so less frequently and for a shorter period of time daily than chickens ranging in summer. The number of chickens ranging and the frequency and duration of range visits increased over the first two weeks of range access and stabilised thereafter. More chickens entered and exited the range through particular doors in the shed. More chickens ranged in the morning and evening compared to the middle of the day. Ranging behaviour decreased with increased rainfall and shed dew point. This study provides knowledge regarding ranging behaviour in commercial conditions that may guide improvements on farm to provide chickens with optimal ranging opportunities.

Abstract

Little is known about the ranging behaviour of chickens. Understanding ranging behaviour is required to improve management and shed and range design to ensure optimal ranging opportunities. Using Radio Frequency Identification technology, we tracked 300 individual broiler chickens in each of four mixed sex ROSS 308 flocks on one commercial farm across two seasons. Ranging behaviour was tracked from the first day of range access (21 days of age) until 35 days of age in winter and 44 days of age in summer. Range use was higher than previously reported from scan sampling studies. More chickens accessed the range in summer (81%) than winter (32%; p < 0.05). On average, daily frequency and duration of range use was greater in summer flocks (4.4 ± 0.1 visits for a total of 26.3 ± 0.8 min/day) than winter flocks (3.2 ± 0.2 visits for a total of 7.9 ± 1.0 min/day). Seasonal differences were only marginally explained by weather conditions and may reflect the reduction in range exposure between seasons (number of days, hours per day, and time of day). Specific times of the day (p < 0.01) and pop-holes were favoured (p < 0.05). We provide evidence of relationships between ranging and external factors that may explain ranging preferences.

The Impact of Group Size on Welfare Indicators of Ewes during Pregnancy

Group size (GS) and space allowance have major implications for the welfare of production species, however their effects are often confounded. In a previous study we investigated the impact of varying space allowance at constant GS. In the present work we report the consequences of varying GS on pregnant ewes while controlling space allowance. We housed ewes at 6 (GS6) or 12 ewes/enclosure (GS12), while controlling space allowance to 1.5 m2/ewe (3 enclosures/treatment), and necessarily varying enclosure size. Therefore, when indicating GS effects we implicitly reflect a confounding effect with that of enclosure size. Movement, use of space, behaviour, serum cortisol concentration and body condition score (BCS) were collected during the last 12 gestation weeks. Movement, use of space, and behaviour were collected every other week, during 2 days/week, using 10 minute continuous scan samplings. Blood was collected during weeks 10, 13, 17, and 21 of gestation, and BCS during weeks 15 and 21. Data were analysed using repeated measures, generalized linear mixed models, with GS, week, and their interaction as fixed effects, and enclosure as random effect. GS mainly affected movement and use of space. GS12 ewes walked longer distances using longer steps (P<0.001). An interaction GS by week was observed for angular dispersion (P<0.0001), which was smaller for GS12 from week 10 onwards. Initial restlessness levels were lower for GS12, as shown by the reduced frequency of location changes (P<0.0001). Furthest and mean neighbour distances increased with GS (P<0.0001). The effect of GS on behaviour was only evident for eating behaviour as an interaction with gestation week (P<0.05). Changes in behaviour, movement and use of space along the study indicated an activity peak during weeks 3 to 5. Cortisol changes during gestation (P<0.01) also reflected this activity peak, while BCS (P<0.001) reflected normal physical condition changes during pregnancy. Although the separate effects of GS and enclosure size cannot be disentangled, we conclude that if enough space/ewe is given during gestation, larger GS will result in larger effective space, and no major implications for the welfare of ewes should be expected as GS increases. Ewes will adapt their movement patterns and use of space to enclosure size, and no further behavioural, physiological and physical consequences should be expected.

Space availability in confined sheep during pregnancy, effects in movement patterns and use of space

Space availability is essential to grant the welfare of animals. To determine the effect of space availability on movement and space use in pregnant ewes (Ovis aries), 54 individuals were studied during the last 11 weeks of gestation. Three treatments were tested (1, 2, and 3 m2/ewe; 6 ewes/group). Ewes' positions were collected for 15 minutes using continuous scan samplings two days/week. Total and net distance, net/total distance ratio, maximum and minimum step length, movement activity, angular dispersion, nearest, furthest and mean neighbour distance, peripheral location ratio, and corrected peripheral location ratio were calculated. Restriction in space availability resulted in smaller total travelled distance, net to total distance ratio, maximum step length, and angular dispersion but higher movement activity at 1 m2/ewe as compared to 2 and 3 m2/ewe (P<0.01). On the other hand, nearest and furthest neighbour distances increased from 1 to 3 m2/ewe (P<0.001). Largest total distance, maximum and minimum step length, and movement activity, as well as lowest net/total distance ratio and angular dispersion were observed during the first weeks (P<0.05) while inter-individual distances increased through gestation. Results indicate that movement patterns and space use in ewes were clearly restricted by limitations of space availability to 1 m2/ewe. This reflected in shorter, more sinuous trajectories composed of shorter steps, lower inter-individual distances and higher movement activity potentially linked with higher restlessness levels. On the contrary, differences between 2 and 3 m2/ewe, for most variables indicate that increasing space availability from 2 to 3 m2/ewe would appear to have limited benefits, reflected mostly in a further increment in the inter-individual distances among group members. No major variations in spatial requirements were detected through gestation, except for slight increments in inter-individual distances and an initial adaptation period, with ewes being restless and highly motivated to explore their new environment.

Animal Welfare and Food Safety Aspects of Confining Broiler Chickens to Cages

In most areas of the world, broiler chickens are raised in floor systems, but cage confinement is becoming more common. The welfare of broiler chickens in cages is affected by movement restriction, poor bone strength due to lack of exercise, and prevention of key behavioral patterns such as dustbathing and ground scratching. Cages for broiler chickens also have a long history of causing skin and leg conditions that could further compromise welfare, but a lack of controlled studies makes it difficult to draw conclusions about newer cage designs. Cage environments are usually stocked at a higher density than open floor systems, and the limited studies available suggest that caging may lead to increased levels of fear and stress in the birds. Further, birds reared on the floor appear less likely to harbor and shed Salmonella, as litter may serve as a seeding agent for competitive exclusion by other microorganisms. Cages for laying hens used in egg production have met with substantial opposition due to welfare concerns and caging broiler chickens will likely be subject to the same kinds of social disapproval.

Space needs of broilers

There is continuing debate about the space needs and requirements of broiler chickens, The aims of this study were to measure the amount of floor area a six-week-old broiler occupies for different behaviours and to use the obtained results in two models to estimate the number of birds that can be kept per m2 in large flocks simulating different levels of behavioural synchronisation. Photographs were taken of overhead projections of broilers (2.468 kg on average) kept in floor pens of 1 m2 with either eight (low density) or 16 birds (high density) per pen. Individual body space was measured from these photographs for seven behaviours. Posture and density affected body space of the behaviours idle, drinking, and ground pecking. The first model, computing space needed per bird performing a behaviour in relation to flock size, showed that 15.3-15.7 birds m−2 (37.8-38.7 kg m−2) can be housed maximally, based on low density measurements and 18.5-19.4 birds m−2 (45.7-47.9 kg m−2) based on high density measurements. The second model, computing stocking density based on synchronisation of behaviour and body space, showed that 13.7-15.9 birds m−2 (33.8-39.2 kg m−2) can be housed maximally based on low density measurements and 15.4-18.6 birds m−2 (38.0-45.9 kg m−2) based on high density measurements. Results based on high density measurements implied that birds are compressed. Given the restrictions of a limited number of behaviours and no inclusion of movement and social interactions in the models of this study, stocking density in large flocks should not exceed 16 birds m−2 (39.4 kg) because that would lead to compression of birds which will suppress opportunities for behavioural expression and therefore impair welfare.