Pullets are young layer hens before they have reached sexual maturity and start laying eggs. At one day of age, female chicks are transferred to rearing systems until they are around 16 weeks of age, when they are then transferred to layer hen housing for the remainder of their productive life [1].
The design of a pullet rearing systems is critical to ensuring that pullets are ‘trained’ so they may adapt to their layer hen housing system. When pullets are reared in environments that do not prepare them for their intended layer hen housing system it can lead to the development of abnormal behaviours and increase the risk of keel bone (extension of the breastbone/sternum) related injuries or fractures later in life.
Why is pullet training and rearing important?
For pullets and layer hens to experience good welfare they must have both their physical and mental needs appropriately met. Pullets and layer hens, regardless of their housing system, are highly motivated to perform natural behaviours including dustbathing, foraging, perching, and nesting (for layer hens). Rearing systems are important for providing birds the opportunity to engage in these highly motivated natural behaviours. This may be done by providing perches, platforms, or a multi-tiered environment to teach them jumping, encourage perching and perform exploratory behaviours.
Newly hatched chicks begin developing natural behaviours and fear-related behaviours within the first 24 hours of life. Within the first 10 days of life, they are particularly sensitive to learning about food, ground pecking and dustbathing behaviour, and begin being motivated to perch [2–4]. This means it is important to expose young birds to appropriate substrates, perches and environmental enrichment during rearing to encourage the development of these natural behaviours at lay [1].
Some of the important behavioural needs of pullets and layer hens which housing systems should accommodate for include:
- Dustbathing: Birds dust bathe to clean and maintain feathers, remove oil build-up from feathers and parasites, and to also help regulate their body temperature.
- Foraging: Birds are naturally motivated to scratch and peck at the ground when provided the opportunity even when feed is available in troughs.
- Perching: Birds have a strong motivation to access perches, particularly at night while they are resting, so that they can feel safe from potential predators and escape from other birds.
- Nesting: Birds when they are sexually mature are naturally motivated to seek out nests to lay their eggs. Normally, nest box training occurs in the first few weeks after pullets are transferred to their layer hen housing system. It is therefore important to train pullets to use nests during rearing so that they may adapt more easily and use nests appropriately once they begin laying eggs.
Providing perches and complex environments during rearing also helps improve pullets’ adaptability, spatial navigation and ability to move vertically up and down levels as they grow. Early access to perches and structurally complex and enrichment environments can assist in reducing collision risks with other birds and objects, as well as improves bone health reducing the incidence of keel bone related injuries later in life [1, 5]. To ensure pullets have the best opportunity to easily adapt and navigate their layer hen housing systems after transfer, it is important they are reared in the same or similar environment to that of their intended layer hen housing [6].
What are the different types of rearing systems for pullet training?
Rearing systems may be caged systems or cage-free systems.
Caged rearing systems
Caged rearing systems involve raising pullets in cages after which they are then transferred to a caged layer hen system, such as battery or furnished layer hen cages. These caged rearing systems may be barren battery cage or furnished cage systems. Furnished cage rearing systems provide birds with perches, nest boxes and scratching pads to encourage birds to perform some highly motivated natural behaviours and assist with nest box training [1].
The use of barren battery cage systems during rearing or laying has inherent animal welfare concerns due to confinement and behavioural restriction. While furnished cage systems promote greater expression of natural behaviours, the bird’s full behavioural repertoire can still not be met. To read more about battery cages, click here.
Cage-free rearing systems
Indoor rearing systems are where pullets may be housed either in large sheds on the floor (floor-based system) or in a shed with multiple levels (multi-tiered/aviary systems). These systems provide pullets greater freedom to move around and opportunities to carry out natural behaviours such as stretching and flapping their wings [1]. These systems will often also provide birds with perches, nest boxes and litter material on the floor of the shed.
In multi-tiered/aviary rearing systems, chicks/pullets may initially be confined to a single tier for the first few weeks of their life. The cage doors are then opened providing birds access to the entire shed containing single or multiple raised levels of perches or slatted platforms. The amount and complexity of the levels increases over time to train pullets how to perch, navigate complex housing systems, and nest seek. Allowing pullets the opportunity to learn how to perform these natural behaviours later assists them to adapt to their intended layer hen housing system.
Free-range rearing systems are where pullets are housed in a large shed usually with perches and nest boxes and are provided outdoor area access during the day once they are fully feathered. By providing an outdoor area, these systems allow pullets further opportunities to perform natural behaviours like dustbathing, exploratory and foraging behaviours. At night, pullets are kept locked in the shed to keep them safe from predators.
What are the animal welfare issues with pullet training and rearing?
Encouraging learning and expression of natural behaviours in pullets during rearing is critical to ensure good welfare later in the future. Welfare implications that may arise if pullets are not properly trained or are reared in barren environments include feather pecking, keel bone related injuries and fractures, or developing abnormal behaviours such as stereotypies.
Electrified wires
Electrified wires (often called ‘hot wires’) are sometimes used to prevent birds from perching on feed and water lines, or nesting on the floor instead of in their nests to prevent floor eggs. Floor eggs require manual collection, and may indicate welfare concerns, such as poor access to nests or reluctance to use nests (especially if they are soiled). Hot wires pose a risk to bird welfare from potential pain, injuries, and burns when used inappropriately. In most cases these wires are only used during the training period and then switched off once birds have learnt to use their nests. The use of hot wires should be avoided, and rearing should focus on good management and husbandry practices to ensure birds are appropriately trained. Once in the layer hen housing system, ensuring nests are appropriate to encourage birds to use them is critical to preventing floor eggs.
Feather pecking and abnormal behaviours
Feather pecking is an injurious behaviour where birds will peck and pull out the feathers of other birds. This behaviour causes pain to the bird whose being pecked and can result in injuries, cannibalism, and in some cases death. Pullets reared in inappropriate rearing systems or not provided litter during rearing have been shown to develop displacement preening and redirected foraging behaviours, which can result in feather pecking [7–8]. Other factors during rearing which may increase the risk for feather pecking include frequent diet changes; high ammonia and/or carbon dioxide levels; and inappropriate lighting colour, intensity or programs. [9–10].
When pullets are reared in inappropriate environments or unable to perform highly motivated natural behaviours such as perching, foraging, or nesting they may also become frustrated and develop abnormal behaviours as layer hens. These abnormal behaviours may include vocalisations, pacing, head movements, stepping on the spot, and displacement preening [11–13].
Keel bone injuries and fractures
Keel bone injuries or fractures can occur in layer hens when they fall from heights or have collisions with objects or structures in the shed. Keel bone injuries are a serious welfare concern as they cause pain and limit bird movement [14]. Pullets reared in systems without perches or in systems which differ significantly from their intended layer hen housing may be at an increased risk of experiencing keel bone injuries. This is because they often have poorer spatial navigation and weaker bone and leg health in comparison to pullets reared in more spatially complex environments such as multi-tiered aviaries [15].
Overall, rearing pullets in an enriched and structurally complex environments helps improve their ability to adapt to the intended layer hen housing system, a s well as improving leg and bone health and decreasing the risk of bone related injuries later in life.
References
[1] Norman KI [2021] Experimental improvements in pullet rearing, PhD Thesis, University of Bristol, Bristol, United Kingdom.
[2] Vestergaard KS, Baranyiova E [1996] Pecking and scratching in the development of dust perception in young chicks. Acta Veterinaria Brno 65: 133-142.
[3] Vestergaard KS et al [1999] Regulation of dustbathing in feathered and featherless domestic chicks: the Lorenzian model revisited. Animal Behaviour 58:1017-1025.
[4] Nicol CJ et al [2001] Influence of prior exposure to wood shavings on feather pecking, dustbathing and foraging in adult laying hens. Applied Animal Behaviour Science 73:141-155.
[5] Colson S et al [2008] Influence of rearing conditions of pullets on space use and performance of hens placed in aviaries at the beginning of the laying period. Applied Animal Behaviour Science 111:286–300.
[6] Widowski T, Torrey S [2018] Rearing young birds for adaptability In Advances in Poultry Welfare, Mench, J.A., Eds.; Woodhead Publishing: Cambridge; pp. 49-76.
[7] Lamberton SL et al [2010] The risk factors affecting the development of gentle and severe feather pecking in loose housed laying hens. Applied Animal Behaviour Science 123:32-42.
[8] Weeks CA, Nicol CJ [2006] Behavioural needs, priorities and preferences of laying hens. Worlds Poultry Science Journal 62:296-307.
[9] Drake KA et al [2010] Influence of rearing and lay risk factors on propensity for feather damage in laying hens. British Poultry Science 51:725-733.
[10] Gilani AM et al [2013] The effect of rearing environment on feather pecking in young and adult laying hens. Applied Animal Behaviour Science 148:54-63.
[11] Meijsser FM, Hughes BO [1989] Comparative-analysis of pre-laying behavior in battery cages and in 3 alternative systems. British Poultry Science 30:747-760.
[12] Yue S, Duncan IJH [2003] Frustrated nesting behaviour: relation to extra-cuticular shell calcium and bone strength in White Leghorn hens. British Poultry Science 44:175-181.
[13] Duncan IJH, Woodgush DG [1972] Analysis of displacement preening in domestic fowl. Animal Behaviour 20:68-71.
[14] Nasr MA et al [2013] The effect of keel fractures on egg production, feed and water consumption in individual laying hens. Poultry Science 54:165-170.
[15] Casey-Trott TM et al [2017] Rearing system affects prevalence of keel-bone damage in laying hens: a longitudinal study of four consecutive flocks. Poultry Science 96:2029-2039.
