Variation in litter occupancy and dust bathing patterns among layer strains following periods of litter restriction.

Producers are moving toward cage-free systems to house laying hens. These include aviary styles with multilevel wire enclosures and litter areas on the floor. In aviaries with doors hens can be confined within the tiered enclosure, which can be done to promote oviposition in nests and prevent hens from laying eggs in litter. However, there are multiple genetic strains of laying hen used in the egg industry, and some show different temporal patterns for key behaviors that could affect when they want to be on litter. For example, though dust bathing by laying hens is typically considered to peak in early afternoon, there may be variation in timing of motivation to dust bathe among strains. Differences in hens' temporal patterns, coupled with aviary configurations or management practices, may restricts birds' ability to perform important behaviors, such as dust bathing (DB), when they would most prefer to do them. Our objective was to determine if there were strain differences in the temporal pattern of DB. We examined the timing of DB in 4 strains of laying hen (Hy-Line Brown [HB], Bovans Brown [BB], DeKalb White [DW], and Hy-Line W36 [W36]) housed in aviaries using 144 hens of each strain per aviary unit (4 units/strain). We recorded the number of hens DB and on litter using instantaneous scan sampling every 5 min using video collected at 26 and 28 wk of age beginning at 11:35 (when litter access began each day) to 20:00 (lights off). Brown strains acclimated to litter access more slowly than white strains. Hens of all strains DB most often soon after gaining access to litter, and more white hens (DW and W36) DB simultaneously and in the presence of more conspecifics. Further examination of diurnal rhythm of behaviors, such as dust bathing, under unconstrained conditions by a range of genetic strains of laying hens is needed to design management practices and aviary styles that best meet hens' needs.

Dust bathing in laying hens: strain, proximity to, and number of conspecifics matter.

As housing laying hens in aviaries becomes more common, understanding relationships between social context and performance of key behaviors, such as dust bathing (DB), is important. Expression of behaviors may be increased or repressed by the presence of conspecifics, and degree of behavioral synchrony can affect per hen resource allocation. We investigated relationships between number of hens on litter, number of hens simultaneously DB, and interbird distances (IBD) on space used to DB and duration of DB bouts across 4 laying hen strains (Hy-Line Brown [HB], Bovan Brown [BB], DeKalb White [DW], and Hy-Line [W36]) at 28 wk of age. Brown hens needed more space to DB than white hens (HB 1125.26; BB 1146.51 vs. DW 962.65; W36 943.39 cm2; P < 0.01). More white hens occupied litter at once (43 DW, 41 W36 vs. 28 HB, 31 BB; P < 0.01), and more white hens DB simultaneously than brown hens (11 DW, 19 W36 vs. 4 HB, 4 BB; P < 0.01). Brown hens had larger average IBD (HB 13.99, BB 15.11 vs. DW 8.39, W36 7.85 cm; P < 0.01) and larger minimum IBD (HB 6.76, BB 7.35 vs. DW 1.63, W36 1.79 cm; P < 0.01) but shorter DB durations than white hens (HB 7.37, BB 9.00 vs. DW 13.91, W36 15.16 min; P < 0.01). White hens' DB area decreased if number of hens on litter increased (DW 0.85; W36 0.79 cm; P < 0.05) or minimum IBD decreased (DW 3.66, W36 2.98 cm; P < 0.01). Brown hens' DB bout duration decreased as number of hens on litter increased (HB 0.87, BB 0.95 min; P < 0.01), number of other hens DB increased (HB 0.75, BB 0.69 min; P ≤ 0.02), or minimum IBD decreased (HB 2.39, BB 2.31 min; P < 0.01). In response to smaller IBD and more hens on litter simultaneously, DW and W36 hens minimize DB area while BB and HB hens shorten DB bouts, potentially terminating bouts before fulfilling their needs. Variations in DB behavior among strains should be considered when planning and stocking laying hen aviaries.