The rearing period — from hatch to first egg at around 16-18 weeks — establishes the physiological, immunological, and behavioural foundations for laying hen welfare throughout the production period. Welfare investments during rearing deliver dividends in laying hen health, welfare, and production.
The first weeks of life are critical for pullet development. Social learning occurs rapidly — chicks learn food recognition, foraging techniques, and social behaviour from flock-mates. Fear responses and human-animal relationships are established early; pullets reared with frequent positive human contact are less fearful throughout their lives. Immune system development requires appropriate pathogen exposure (through housing and mixed-age contact) to develop functional immunity before the immunological challenges of production.
The housing system in rearing profoundly affects suitability for the laying environment. Pullets reared in cages and transferred to aviary or barn systems lack the experience needed to navigate multi-tier environments — they may be unable to locate perches, struggle to access upper-tier feeders, and show higher mortality. Rearing pullets in systems matching their laying environment (aviary rearing for aviary layers, range access for free-range production) improves welfare outcomes in the laying period. 'System mismatch' is an important and often overlooked welfare issue.
The rearing period is the primary window for vaccination against diseases that will challenge hens in lay. Effective vaccination programmes against Newcastle Disease, Infectious Bronchitis, Marek's Disease, Avian Rhinotracheitis, and Egg Drop Syndrome protect laying hen welfare. Live vaccines (spray, drinking water, or eye-drop) stimulate immunity effectively but may cause transient mild respiratory signs — appropriate for the rearing period rather than during lay. The welfare cost of disease in laying hens is directly reduced by adequate rearing-period vaccination.
Enrichment during rearing shapes behavioural repertoire for life. Pullets provided with perches develop confident roosting behaviour and suffer fewer leg injuries in systems with elevated perches. Litter access develops foraging behaviour and reduces feather pecking risk. Novel objects and varied environments reduce fearfulness and improve adaptability. The behavioural toolkit assembled during rearing determines how effectively pullets cope with the challenges of the laying period.
Rearing nutrition affects lifetime welfare. Pullets need to reach appropriate body weight and uniformity at point of lay — underweight pullets produce smaller eggs with increased prolapse risk; overweight pullets have reduced laying persistence. Dietary transitions (chick, grower, developer, pre-lay diets) must be appropriately timed and managed. The pre-lay period is particularly important — introducing higher calcium before the onset of lay (rather than abruptly at point of lay) prepares bones for the calcium demands of egg production.
Key welfare indicators during rearing include: body weight and uniformity (measured at regular intervals), feather cover and condition, mortality rates and causes, vaccination response assessment, and behavioural observation (activity, exploration, perch use, foraging behaviour). Assessing these indicators regularly enables management adjustments before welfare problems become entrenched. Rearing welfare assessment predicts laying welfare outcomes — investing in rearing welfare pays returns across the entire laying cycle.