Influence of prior exposure to wood shavings on feather pecking, dustbathing and foraging in adult laying hens.

It has been proposed that chicks acquire substrate preferences during an early 'sensitive' period. If a suitable substrate is absent during this period birds may develop alternative preferences for pecking at feathers. The aim of this study was to examine whether early substrate exposure has durable effects on the subsequent behaviour of adult hens. The effects of duration of substrate exposure, substrate change, age at exposure and time since exposure on adult bird behaviour were examined. From days 1 to 210, 144 laying strain birds were housed in pairs in pens with wire floors. The floors were replaced with solid floors covered in wood shavings at different ages and for different durations by allocation to 1 of 12 treatments. Adult birds that had never experienced shavings performed significantly more feather pecking than birds in any other treatment group. Thus, exposure to shavings, even for the minimum exposure duration of 10 days, was protective. However, current substrate was of great importance and adult birds housed on shavings performed significantly more ground pecking and less feather pecking than birds on wire, regardless of previous experience. From day 211 all hens were given shavings or straw, presented alternately for five 24h sessions over 10 consecutive days. Birds foraged on both substrates and their foraging behaviour was not influenced by previous experience. Dustbathing occurred primarily on shavings and was significantly influenced by the age at which birds had previously been exposed to shavings. Dustbathing on shavings was fairly constant throughout the 10-day test period in all groups, suggesting that relatively stable preferences had developed. A secondary 'sensitive period' for the formation of adult dustbathing substrate preference may have superseded the early 'imprinting' process. However, adult behaviour was generally flexible and strongly influenced by current substrate.