Differences in Fearfulness Indicated by Tonic Immobility Between Laying Hens in Aviaries and in Cages
Abstract:The aim of this study was to investigate whether there were differences in fearfulness between laying hens (Gallus gallus domesticus) housed in aviaries and in cages. The tonic immobility (TI) test was used to assess the fearfulness. Norwegian light hybrid White Leghorn hens were housed in battery cages and in three types of aviaries: the Marielund, the Laco-Volétage and the Tiered Wire Floor. Each system housed about 1,500 birds. Tests were performed on 50 birds per housing system at 70 weeks of age in one laying flock and at 30 and 70 weeks of age in the next.
At 30 weeks of age in the second laying flock, the duration of the tonic immobility response was unaffected by type of system. At 70 weeks, however, hens in cages showed tonic immobility of longer duration than hens in aviaries, in the first as well as in the second laying flock. No differences in TI between hens from the three types of aviaries were found. The duration of TI did not correlate with plumage condition or body-weight, except for a longer duration of TI with poorer plumage condition in aviaries at 30 weeks. These results indicate that the fearfulness of hens in cages, as measured by the TI test, increased considerably with time. The lower fearfulness shown by hens in aviaries suggests that this important aspect of welfare is more secured in avian'es than in cages.