Synchronization of behavior among laying hens in battery cages

Abstract

An investigation was carried out to assess synchronization of behavior among hens in battery cages. Two genetic stocks of pullets were raised in battery cages and housed as pairs in laying cages at 21 weeks of age (96 cages per stock). Hens of the same genetic stock occupied adjacent pairs of cages. The laying phase was divided into 28-day periods, and in Periods 1, 3, 5, 7, 9 and 11, time-lapse videorecordings were made of four pairs of cages per day over a sequence of 4 days. Each pair of cages was viewed by one camera, allowing simultaneous recording of the behavior of the hens in each cage. For each tape, 60 records of the behavior of each hen were obtained at equal intervals over 8 h. Behavioral dyads were defined as the concurrent behavioral states of a pair of hens at each point of observation. The frequency of occurrence of each dyad was compared with that expected given random manifestation of the behavior of hens relative to other hens. Cagemates showed a decided tendency to synchronize behavior. Six of eleven possible dyads of the same behavior occurred more than expected, many of them with a very high degree of statistical significance. Behavioral dyad differences from expected occurrence (DFEs) were consistently greater within cages than between cages for dyads of the same behavior, suggesting that social factors promoted synchronization of behavior in cages. Nonetheless, some degree of behavioral synchronization was apparent between cages as well. The potential effects of a desire to synchronize behavior are considered with regard to egg production and well-being in a battery cage environment.