Welfare of broilers on farm

This Scientific Opinion includes the welfare assessment of the following broiler categories: day-old chicks, broiler breeders and broilers for meat production. In addition, it is recommended to harmonize the assessment of the following ABMs in relation to the assessment of on-farm welfare at slaughter: 'wounds', 'carcass condemnation', 'total on-farm mortality' and 'FPD'.

Introduction

Background and Terms of Reference as provided by the requestor

Define qualitative or quantitative measures to evaluate the welfare consequences (animal-based measures) (General VV 3). Provide recommendations to prevent, mitigate or correct the welfare consequences (resource and management based measures) (General VV 5).

Interpretation of the Terms of Reference

Specific TeR 1) Welfare of fast-growing chickens in barns and risks related to: .. a) air and floor temperature, b) access to feed and water, c) space allowance,. Hazards should be interpreted as risk factors or exposure variables that lead to welfare consequences.

Data and methodologies

Data from literature

To address the specific ToR 1c 'welfare of fast-growing chickens housed in a house and the risk associated with space allowance', a new quantitative behavioral model was developed which considered nine essential broiler behaviors in addition to EKE. In the context of this scientific opinion, when 90-100% certainty was attributed to the conclusion, this was not included in parentheses.

Data obtained from the questionnaire to European Forum of Farm Animal Breeders (EFFAB)

As many hazards are considered in this scientific opinion and described in different places, the main recommendations to prevent or correct the hazards and to reduce the WCs are included in section 4.1 to summarize them. For the purposes of this scientific opinion, chickens with a growth rate of less than 50 g/day are considered slow growing and chickens with a growth rate of more than 50 g/day are considered fast growing.

Methodologies

General ToRs
Speci ﬁc ToRs

Speciﬁc ToR 1c
Speciﬁc ToR 2
Speciﬁc ToRs 3 and 4

Literature searches

General ToRs
Speci ﬁc ToRs
Uncertainty assessment

Stabilized values are based on the average of the lowest and highest two values for the stabilized minimum and maximum. Stabilized values are based on the average of the lowest and highest two values for the stabilized minimum and maximum.

Assessment

Broiler production in the European Union

In the conclusions, when the certainty was 90 to 100%, it is not indicated in the accompanying text. Uncertainty is only specified (in brackets at the end of each conclusion) in case the certainty is less than 90%.

Production cycles of broilers and respective animal categories

Day-old chicks hatched in hatcheries or on-farm
Broiler chickens for meat production
Broiler breeders

Broiler breeders are the parents and previous generations (eg, grandparents, great-grandparents) of commercially used broilers (broiler chickens for meat production). Selection targets for efficient and rapid growth rates and breast meat gain in broilers are negatively correlated with broiler fertility (Siegel and Dunnington, 1988).

Husbandry systems per animal categories

Day-old chicks hatched in hatchery
Day-old chicks hatched on farm
Chickens for meat production kept on ﬂoor systems (indoor)
Chicken for meat production kept on Floor systems (Indoor) with covered veranda
Chicken for meat production kept on ﬂoor systems with free range
Chicken for meat production kept in mobile systems with free range (niche production)
Broiler breeders kept in ﬂoor systems
Broiler breeders kept in individual unfurnished cages
Broiler breeders kept in furnished collective cages
Broiler breeder kept in ﬂoor system with multi-tier systems

Access to the covered porch depends on the temperature requirements and therefore the age of the animals. A large part of the floor is covered with litter, because mating is supposed to take place in the litter.

Highly relevant WCs, related ABMs on farm for broilers, hazards, preventive and corrective

List of welfare consequences that were ranked as highly relevant to broiler chickens
Description of the welfare consequences identiﬁed as highly relevant in the context of broiler

Measurement of ABMs
Bone lesions
Cold stress
Inability to perform comfort behaviour
Inability to perform exploratory or foraging behaviour
Gastro-enteric disorders and infectious diseases
Prolonged hunger
Prolonged thirst
Heat stress
Handling stress
Isolation stress
Locomotory disorders
Predation stress
Restriction of movement
Resting problems
Group stress
Soft tissue lesions and integument damage
Umbilical disorders
Inability to avoid unwanted sexual behaviour
Sensory under and/or over stimulation
Link between ABM, welfare consequences and category of bird

Definition Temperature measured on the surface of the day-old chick (wing, head, leg, back) (Vieira et al., 2016). It results from a hematoma and is often without tearing of the skin (Cockram et al., 2020).

Enclosure requirements in broiler production (broiler breeders, broiler chickens (fast- and slower-

Management

Space allowance (Speci ﬁc ToR 1c)
Minimal height at any point
Minimum usable area
Light
Temperature (Speci ﬁc ToR 1a)
Air quality and dust (speciﬁc ToR 1d)
Group size
Covered veranda
Outdoor range

Equipment

Perches
Tiers/Platforms
Litter
Nests for breeders
Feeders
Drinkers
Enrichment

Therefore, a minimum group of two people is necessary to avoid isolation stress (Marx et al., 2001). The use of enrichment such as alfalfa has also been reported to promote outdoor range use in broilers (Riber et al., 2018). This applies to the fast-growing Ross 308 as well as slower-growing hybrids such as Sasso (Gebhardt-Henrich et al., 2018).

Much more, ie 50% of the floor was covered with partially raised plastic tiles in the study by May et al. In the study of May et al. 2022), the birds were mostly inactive when perched on the slats. Slower-growing broilers use and benefit from enrichment probably more than fast-growing hybrids (de Jong et al., 2021).

Impact of genetics on broiler welfare

In particular, in broilers, enrichment items should increase their activity to prevent movement disorders (Kaukonen et al., 2017b). Breeders of pitted chickens have more tusks bone damage than breeders of non-pitted chickens (Gebhardt-Henrich et al., 2017b). In the paper of Vissers et al. 2019) with some slower-growing hybrids maintained under reduced stocking densities, production costs increased slightly while animal welfare improved significantly.

The same results, namely better health and more positive behavior, were found in two broiler hybrids consuming less than 50 g per day compared to fast-growing hybrids (Rayner et al., 2020). Some of these factors interact, such as slower growing hybrids in lower stocking density and provided with enrichment achieve on average higher welfare scores than the fast growing hybrids (de Jong et al., 2022). The required feed restriction, especially during rearing, is more severe and of longer duration for fast-growing than for slower-growing hybrids (Puterﬂam et al., 2006; Arrazola and Torrey, 2021).

Feed restriction & prolonged hunger in broiler breeders (speci ﬁc ToR 3a)

Introduction
Feed restriction of broiler breeders

Description of feed restriction in broiler breeders
Welfare consequence linked to feed restriction
ABMs to measure hunger due to feed restriction in breeders
Description of the main feed regimens currently applied to reduce the hunger due to feed

In recent decades, broilers have been selected for their fast growth and high feed efficiency (Zuidhof et al., 2014). This feeding limitation is most severe during the breeding season and is more severe in very fast-growing hybrids than in slower-growing hybrids (Puterflam et al., 2006; Dixon, 2020; Arrazola and Torrey, 2021). Famine can be alleviated by relaxing feed restrictions while adopting a higher growth trajectory without negative consequences for health and reproduction (Afrouziyeh et al., 2021).

Birds with the SAD diet had a higher feeding motivation (presumably a higher hunger level) at the end of laying during production (Arrazola et al., 2019b). Similarly, de los Mozos et al. 2017) claimed that diluting the feed reduced the feeling of hunger. However, PLF is a rapidly developing field and new developments must be followed (Yang et al., 2021).

Mutilations in broiler breeders (Speciﬁc ToR 3b)

Mutilations in broiler breeders leading to soft tissue lesions and integument damage
ABMs
Hazards
Preventive measures
Corrective and mitigative measures
ABMs
Preventive and Mitigation measures

Indicators of distress include 'distress calls' and 'resistance to handling' and 'escape attempts' at the time of the event, followed by deviations from expected growth rate indicated by impaired growth rate relative to other birds and changes in the bird's time budget after mutilation. It may be possible to provide an analgesic during the time of amputation to reduce the pain associated with the procedure. Social animals such as chickens experience isolation stress when housed separately and as a result are prone to frustration and develop stereotyped behaviors such as too frequent clipping of a part of the feather leading to feather damage, e.g.

The severity of this WC will depend on staff composure and caution, so training staff on good handling practices will prevent handling stress. Wire floors can cause foot injuries and toes can get caught in poorly designed wire structures, causing soft tissue and sheath injuries. In addition, due to the small size of the individual cages, the feathers are in constant contact with the wire and can swell and break.

The welfare of fast-growing chickens in barns and the risks associated with access to feed and

Access to feed and water for day-old chickens
Access to feed and water during rearing

During the growth period, the height of drinkers and feeders is adjusted to the height of the chickens. Bell feeders and drinkers are usually positioned so that the end of the bell feeder or drinker is at the height of the top of the bay (Aviagen, 2018a). The size of the smallest chickens in the flock will determine the height of the feeders and drinkers, and the farmer will observe feeding and drinking behavior to adjust the height of the feeders and drinkers.

As these are usually a small part of the flock, the farmer must pay attention to these chickens during the daily control of the flock and, when there is no other option, kill the chickens using the appropriate method to prevent (further) suffering ( EFSA AHAW Panel, 2019). Body weight loss' has been identified as the ABM for 'prolonged starvation' in day-old chicks (section 3.4.2.21). Impaired growth rate' has been identified as the ABM for 'prolonged starvation' in broilers and also applies to broilers (section 3.4.2.7).

Welfare of Day-Old-Chicks until they reach the rearing or breeding farms: hazards under hatchery

Introduction
Sensory under and/or overstimulation

ABMs
Hazards

Prolonged hunger and thirst

ABMs
Hazards

Resting problems

ABMs
Hazards

Handling stress

ABMs
Hazards

Similarly, chickens that are unable to walk (walking reality 4 and higher) will not be able to reach feeders and drinkers and will suffer from prolonged hunger and thirst (Weeks et al. , 2000). Access to food and water is usually delayed for 24–48 h, sometimes longer, after hatching in chicks (de Jong et al., 2016a). A meta-analysis of the effects of food and water deprivation revealed long-term negative effects on mortality and performance starting after a mean of 48 h (range: 36–60 h) of deprivation (de Jong et al., 2017).

Moreover, prolonged thirst can result in hibernation and prostration of birds (Borges et al., 2004). Early access to food and water has been hypothesized to stimulate the development of the gastrointestinal system (Willemsen et al., 2010a). Additionally, a variety of fear tests can be used to assess fear response to treatment (Giersberg et al., 2020).

The assessment of Animal Based Measures collected in slaughterhouses to monitor the level of

Introduction
Relevant ABMs
Selected animal-based measures

Total mortality (on-farm)
Carcass condemnations
Wounds
Footpad dermatitis

This ABM has already been recorded in the majority of the EU countries due to the current broiler legislation. While poorer herd uniformity was associated with both first-week mortality and total mortality (Vasdal et al., 2019a). Moreover, there is great variation between meat inspectors in recording the reasons for condemnation.

Wounds on the crest and on the back of the head can be used as a proxy for aggressive interactions between birds (Welfare Quality Network, 2019). They have also been shown to be associated with the presence of pathogens, and a high percentage of birds affected by severe foot pad lesions may be predictive of the flock being Campylobacter positive (Alpigiani et al., 2017). On the other hand, if the assessment is automated (using videos), all animals in the herd can be inspected.

Conclusions and recommendations

Answers to General ToRs

Bone lesions

Conclusions
Recommendations

Cold stress

Conclusions
Recommendations

Heat stress

Recommendations

Inability to perform comfort behaviour

Conclusions
Recommendations

Inability to perform exploratory and foraging behaviour

Conclusions
Recommendations

Gastro-enteric disorders and other infectious diseases (GED)

Conclusions
Recommendations

Prolonged hunger

Conclusions
Recommendations

Prolonged thirst

Conclusions
Recommendations

Handling stress

Conclusions
Recommendations

Isolation stress

Conclusions
Recommendations

Locomotory disorders

Conclusions
Recommendations

Predation Stress

Conclusions
Recommendations

Restriction of movement

Conclusions
Recommendations

Resting problems

Conclusions
Recommendations

Group stress

Conclusions
Recommendations

Soft tissue lesions and integument damage

Conclusions
Recommendations

Umbilical disorders

Conclusions
Recommendations

Inability to avoid unwanted sexual behaviour

Conclusions
Recommendations

Sensory under and/or overstimulation

Conclusions
Recommendations

In mobile housing systems with outdoor access, there should be an environmental temperature of at least 17°C in the house (depending on age, sex, weight, hybrid and stocking density) and chickens must always have access to the house. In individual cages, birds should be provided with dry, crisp bedding/material that is available at all times, accessible perches that do not impede movement within the cage, and a nest box for females. The covered porch should be attractive to the birds, thereby encouraging them to use this extra space.

For broilers with outdoor access, fencing systems and a closed house at night should be used to avoid roosting problems due to ground predators. 4.1.15. In case broilers are kept until sexual maturity or later, special measures should be taken to avoid group stress. In addition to a covered porch, sufficiently structured and enriched free-range areas should be provided to promote even more homogeneous distribution of the herd, reducing local stocking density.

Answers to speciﬁc ToRs

Enclosure requirements in broiler production (broiler breeders, broiler chickens (fast- and slower-

Management
Equipment

Feed restriction in broiler breeders (speci ﬁc ToRs 3b)

Conclusions
Recommendations

Housing in individual cages (speciﬁc ToR 3a)

Conclusion
Recommendations

Mutilations of broiler breeders (speci ﬁc ToR 3b)

Conclusion
Recommendation

Access to feed and water (Speci ﬁc ToR 1b)

Conclusions
Recommendations

Welfare of Day-Old-Chicks until they reach the rearing or breeding farms: hazards under hatchery

Conclusions
Recommendations

The assessment of Animal Based Measures collected in slaughterhouses to monitor the level of

Conclusions
Recommendations

Main Recommendations to improve broiler welfare

During early life, that is, the period from hatching right before they are loaded for transport to the rearing house, broilers and broiler breeder chickens are exposed to several practices that are perceived as stressful and have been shown to have either short-term or both short-long-term and long-term adverse effects on chicken welfare. The potential of the transect method for early detection of welfare problems in broilers. Effects of the brooder system on the welfare of broilers early and later in life.

The effect of stocking density on the welfare and behavior of commercially reared broilers. Effect of different monochromatic light-emitting diode colors on broiler behavior and welfare. Influence of stocking density on broiler performance, carcass characteristics and selected welfare indicators.