Nesting behavior of Hy-Line hens in modified enriched colony cages.

Hens are motivated to seek out an enclosed nest site, but it is unclear whether the single communal nest in enriched colony cages (EC) adequately supports nesting. One method to investigate this is to provide an "alternative nest site" and determine the effects on laying location, timing of oviposition, and pre-laying behavior. The objective of this experiment was to determine whether increasing the degree of enclosure in the scratch area would influence egg laying location, time of oviposition, and pre-laying behavior. Hy-Line W-36 hens (n = 1,560) were reared in standard cages and housed in four rooms, each with six Chore-Time EC, at wk 17 (65 birds/cage at 729 cm2 floor space and 62 cm2 nest space per bird). At 21 wk, the scratch area of the enclosed (E; n = 12) treatment cages was fitted with a wire partition and red vinyl curtain; open (O; n = 12) cages were unmodified. The number of eggs laid in each location (nest, middle, scratch) was counted over 4 d. Nest and scratch areas were instantaneously scan sampled every 20min from 0630 h to 1330 h to count the number of sitting hens and the number of eggs. Aggressive pecks, threats, and displacements were counted in each area during a 30 s interval scan (3 scans/time period, 5 periods). Mixed model analyses tested the effect of treatment, time, room, position, and tier. There was no significant main effect of treatment on the percentage of eggs laid in the nest or scratch areas, but E treatment hens were more aggressive (P = 0.027). The numbers of hens sitting and eggs laid in the nest peaked between 0830 h to 0930 h (P < 0.0001), with a peak in displacements between 0800 h to 1000 h (P < 0.0001). Peak laying time occurred later in the scratch area (0930 h to 1030 h). Treatment affected few nesting behavior patterns, and the behavior differences between the nest and scratch areas replicated earlier findings. Hy-Line W-36 hens seemed to perceive the existing nest as satisfactory, with little evidence for competition.