ENVIRONMENT, WELL-BEING, AND BEHAVIOR

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1 ENVIRONMENT, WELL-BEING, AND BEHAVIOR The effect of perch availability during pullet rearing and egg laying on the behavior of caged White Leghorn hens 1 P. Y. Hester,* 2 J. P. Garner, S. A. Enneking,* H. W. Cheng, and M. E. Einstein * * Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; Department of Comparative Medicine, Stanford University, Stanford, CA 94305; and USDA-Agricultural Research Service, Livestock Behavior Research Unit, West Lafayette, IN ABSTRACT Enriched cages, compared with conventional cages, allow egg laying strains of chickens to meet some behavioral needs, including a high motivation to perch. The objective of this study was to determine if perch availability during rearing affected perch use as adults and if perch presence affected eating and drinking in caged White Leghorn hens. Chickens were assigned to 14 cages each with and without 2 round metal perches from hatch to 16.9 wk of age. At 17 wk of age, pullets were assigned to laying cages consisting of 1 of 4 treatments. Treatment 1 chickens never had access to perches (controls). Treatment 2 chickens only had access to 2 round metal perches during the laying phase (17 to 71 wk of age). Treatment 3 chickens only had access to 2 round perches during the pullet phase (0 to 16.9 wk of age). Treatment 4 chickens had access to the perches during both the pullet and laying phase. Each treatment during the adult phase consisted of 9 INTRODUCTION Enriched cages, as compared with conventional cages, for egg-laying strains of chickens allow hens to meet some of their behavioral needs, including their high motivation to perch (Lambe and Scott, 1998; Olsson and Keeling, 2002). In a companion paper of the current study (Enneking et al., 2012a), pullets were given access to 2 perches in a rearing cage from day of hatch to 16.9 wk of age, when they were transferred to laying cages for the current study. Use of the front perch in pullet cages closest to the feed trough during scotophase increased from less than 0.1% at 6 wk of age to 31% at cages with 9 birds/cage for a total of 36 cages. Automatic infrared cameras were used to monitor behavior of hens in each cage for a 24-h period at 19, 24, 29, 34, 39, 44, 49, 54, 59, 64, and 69 wk of age. Behavior was also recorded twice weekly by an observer in the room where the hens were housed during photophase from 25 to 68 wk of age. Behavioral data were analyzed using ANOVA with repeated measures and the MIXED model procedure. A greater proportion of hens without perches as pullets used the rear perch more during both photophase and scotophase than hens with prior pullet perching experience. Eating and drinking activities of caged adult Leghorns were not impaired by their prior experience to perches as pullets or by the presence of perches in laying cages. It is concluded that providing perches in cages to White Leghorns during pullet rearing did not facilitate use of perches as adults. Key words: perch, pullet, laying hen, behavior, White Leghorn 2014 Poultry Science 93 : /ps Poultry Science Association Inc. Received March 18, Accepted June 25, Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement of the USDA. USDA is an equal opportunity provider and employer. 2 Corresponding author: phester@purdue.edu 12 wk of age. Use of the front perch by pullets peaked at 35% at 14 wk of age, and this usage persisted until the end of the pullet phase at 16.9 wk (Enneking et al., 2012b). The back perches were also used by the pullets, but estimates of the number of pullets using the back perch were not possible because the pullets perching on the front perch blocked the view. During photophase, the presence of perches in pullet cages did not interfere with eating and drinking as compared with pullet cages without perches (Enneking et al., 2012b). Pullets raised in a non-cage housing system demonstrated even earlier perch utilization at a higher frequency (Appleby and Duncan, 1989) than the caged pullets with access to perches in the study of Enneking et al. (2012b). Specifically, out of a total of 23 pullets that were 4 wk of age and given access to perches, 21 of them were using the perches within a week (91% usage). Pullets given access to perches later in life at 8, 12, 16, and 20 wk of age did not demonstrate similar usage of perches until 37 wk of age, suggesting that the earlier pullets are exposed to perches, the faster they adapt to perching (Appleby 2423

2 2424 Hester et al. and Duncan, 1989). An additional advantage of early access to perches in non-cage systems was reduced cannibalism of the cloaca during egg laying by hens whose beaks were not trimmed (Gunnarsson et al., 1999). The objective of this study was to determine if experience with perches in cages during the pullet phase affected how hens used perches and other resources during egg laying. Our hypothesis was that pullets given early access to perches would demonstrate more perching activity at the beginning of egg laying as compared with naive pullets with no previous exposure to perches, but as hens aged, the differences in perching activity between treatments would dissipate. We also hypothesized that the presence of perches in laying cages would not affect eating and drinking. MATERIALS AND METHODS Birds and Management White Leghorn female hatchlings totaling 1,046 of the Hy-Line W-36 strain were raised at the Purdue University Research Farm. Standard management and vaccination procedures were used following guidelines from Purdue Animal Care and Use Committee. Infrared beak trimming was performed at the hatchery. Feed and water were provided ad libitum throughout the study. Two nipple drinkers per cage provided water. All diets met or exceeded the Hy-Line W36 management guide (Hy-Line International, ) or the NRC (1994) nutrient recommendations. A starter diet was fed from hatch to 3.9 wk, a grower diet from 4 to 17.2 wk, a prelay diet from 17.3 to 18 wk, and a laying hen diet from 18 wk through the end of the study. Diet specifications can be found in Enneking et al. (2012a) for the pullet phase and in Hester et al. (2013b) for the laying phase. At 1 d of age, chicks were housed in 1 room of the Grower Research Unit in 28 conventional cages. In 14 of the cages, 2 perches were installed 8 cm above the floor in parallel arrangement to the feeder. Perches were manufactured by Big Dutchman (Holland, MI) and were smooth, round, 32 mm in diameter, and made of galvanized steel (Figure 1a). Number of birds per cage, treatment assignment, tier arrangement, cage dimensions, perch placement (Figure 1a) as well as floor, perch, and feeder space/bird are described in detail by Enneking et al. (2012a). At 17 wk of age, 324 birds were transferred to 36 cages in a room in the Purdue University Layer Research Unit. One-half of the cages had 2 perches (Figure 1b). Except for length, these perches were identical to those used in the pullet phase. Perch space per bird was 16.9 cm and allowed all birds to perch simultaneously if desired. Laying cages consisted of 6 banks 3 decks high for a total of 6 cages per bank. The overall height of the bank of cages was 193 cm. The cages were arranged in a single row with an aisle in front and an aisle behind the cages for passage Figure 1. a) Two round metal perches, 32 mm in diameter, were installed in pullet grower cages (0 to 17 wk of age) in parallel arrangement to each other. Perch height for both perches was 8.9 cm (3.5 in) from the cage floor. There was a distance of 18 cm (7 in) between the 2 perches, between the front perch and the feed trough, and between the rear perch and the back of the cage. This figure and caption were published previously by Enneking et al. (2012a). b) Two round metal perches, 32 mm in diameter, were installed in laying cages (18 to 72 wk of age) in parallel arrangement to each other. Perch height for both perches was 8.9 cm (3.5 in) from the cage floor. There was a distance of 14 cm (5.5 in) between the 2 perches and a distance of 17 cm (6.5 in) between the front perch and the feed trough. Between the rear perch and the back of the cage, there was a distance of 14 cm (5.5 in). Two drip nipples were located at the back of each cage near the cage partition. The feeders were located outside of the cage along the front. This figure and caption were published previously by Hester et al. (2013b). of animal caretakers. Within each bank and deck, 1 cage had perches and the remaining cage did not have perches. Therefore, each deck level had 6 laying cages with perches and 6 cages without perches. Cage specifications, floor space allocation, perch placement (Figure 1b), and lighting details are described in Hester et al. (2013b). Treatments Treatments during the pullet phase (0 to 16.9 wk of age) consisted of 14 cages with perches and 14 cages without perches (controls). These birds were divided into 4 treatments during the laying phase (17 to 71 wk of age). Treatment 1 chickens never had access to perches (controls). Treatment 2 chickens only had perch access during the laying phase (17 to 71 wk of age). Treatment 3 chickens only had perch access during the pullet phase (0 to 16.9 wk of age). Treatment 4 chickens had perch access during both the pullet and laying phase. Each treatment consisted of 9 cages (with 9 birds/cage) for a total of 36 cages.

3 Measurements Automatic infrared cameras (Stealth STCI540-IR, Cabela s Inc., Sydney, NE) were used to monitor each cage for a 24-h period at 19, 24, 29, 34, 39, 44, 49, 54, 59, 64, and 69 wk of age. Each camera took a picture every 5 min when there was movement in the cage. Every other photo was later examined for the number of birds perching, drinking, and eating (that is, behavior was measured every 10 min for a 24-h period if hens were active). Hens on the rear perch were counted during both light and dark hours, whereas hens on the front perch were counted only during dark hours. Poor visibility because of high stocking density prevented accurate counting of birds on the front perch during light hours. Birds were recorded as either standing or reclining on the rear perch, and the 2 observations were totaled for rear perch use. Number of birds perching on both perches was recorded during the dark hours; however, postures were not recorded on the front perch due to the poor visibility. Number of hens drinking was recorded at all times. The number of hens eating was determined at 19, 29, 39, 49, 59, and 69 wk of age. Definitions for drinking, eating, and perching behaviors are listed in Table 1. Because of the poor visibility of photographed hens using the front perch during photophase, the number of birds perching was also counted on Tuesdays and Thursdays by an observer in the room. These observations were done twice weekly from 25 to 68 wk of age. Observations occurred in the mornings (approximately 1000 h) and again in the evenings before the lights were turned off (1600 h). The observer began at the first cage, counted the number of birds on the front perch, Table 1. Ethogram of laying hen behaviors in conventional cages Behavior Photographed behavior using infrared camera Drinking Eating Standing on rear perch Reclined on rear perch Perching on front perch Behavioral observation by an observer in the room where the hens were housed Perching Lying on cage floor BEHAVIOR OF CAGED HENS WITH PERCHES Definition back perch, and lying on the floor, then moved to the next cage, until the observer reached the end of the row. The observer then returned to the first cage to begin the count again. This procedure was performed 6 times during each morning and evening observation, and averages were calculated from the 6 counts. It took 30 min to complete each morning and afternoon observation. Definitions for perching and lying on the floor are listed in Table 1. Statistical Analysis 2425 The design was randomized, and data were analyzed using ANOVA with repeated measures (Steel et al., 1997) and the MIXED model procedure of the SAS Institute (2008). A 2 2 factorial arrangement was used for the proportion of chickens eating and drinking with repeated measures over the age of the hens. The main factors were the presence or absence of perches within the pullet or laying cages. Data on the proportion of hens eating and drinking were analyzed only for photophase because these activities stopped when the lights were turned off. For the remaining behaviors collected from infrared cameras, the main effects were the pullet perch treatment, photoperiod (photophase vs. scotophase), and the age of the laying hen. For data collected by an observer in the room, the main effects were pullet perch treatment, age of the laying hen, and time of the day when the observations were made (morning vs. afternoon). The experimental unit was the cage of 9 laying hens. Arcsine square root transformations were performed on the percentage data. Statistical trends were similar for both transformed and untransformed data; therefore, the untransformed least squares means and A bird s beak is oriented toward the metal tip of the nipple drinker and the beak is within 12.9 cm 2 of the metal tip of the nipple drinker. A bird must meet both criteria to be counted as drinking. The bird s head is extended through the front of the cage with its beak past the lip of the feeder. If a head is a blur (due to the movement of pecking at the feed), it is counted as eating. A bird is standing on the perch closest to the waterers. At least 1 foot is on the perch, and neither foot is on the floor. The bird s legs are extended enough that its chest and belly are not fully resting on the perch. It may be fully standing or crouched down, but not relaxed in a reclined position. Counted during light and dark hours. A bird is reclined on the perch closest to the waterers. The bird s chest and belly are resting on the perch. Its wings are relaxed at its sides. Counted during light and dark hours. Number of birds on the front perch is only counted during dark hours and when the view of the floor underneath the perches is not blocked. If both of these criteria are true, then the number of birds standing on the floor and the number on the rear perch are subtracted from the total number of birds in the cage, giving the number of birds on the front perch. A bird is on the perch; posture is not accounted for. At least 1 foot is on the perch, and neither foot is on the floor. The number of birds perching is counted separately for the front and rear perches. A bird is lying on the cage floor. Its belly is resting on the floor with its wings relaxed and legs tucked underneath it.

4 2426 Hester et al. SEM were presented. The Tukey-Kramer test (Oehlert, 2000) or the SLICE option (Winer, 1971) were used to partition differences among interaction means. RESULTS Behavior Taken by Infrared Cameras During Photophase and Scotophase Drinking and Eating. The proportions of hens drinking and eating during photophase are presented in Table 2. On any day of observation or at any one age (19 to 69 wk), the proportion of hens drinking and eating averaged approximately 4 and 20%, respectively. There were no interactions between the perch treatments and the age of the hens nor were there any interactions between the pullet and adult perch availability (P > 0.05). Drinking activities were not affected by the availability of the perch during either the pullet or laying phases of the life cycle (P = 0.58 and 0.79, respectively). Eating was not affected by prior experience with the pullet perch with proportions similar to controls that did not have perches as pullets (P = 0.11). A greater proportion of hens with access to perches during egg laying was eating as compared with hens without perches (Table 2, P = 0.007). Eating and drinking activities during scotophase were near 0%. Table 2. The effect of perch access in conventional cages on drinking and eating behaviors of White Leghorns during photophase as taken by infrared cameras Treatment Drinking Eating During pullet phase Control (%) Perch (%) SEM n P-value During laying phase Control (%) b Perch (%) a SEM n P-value Interaction (pullet-laying) 2 Control-control (%) Control-perch (%) Perch-control (%) Perch-perch (%) SEM n P-value a,b Least squares means within a column for the laying phase lacking common superscript differ (P < 0.05). 1 Average number of observations per least squares means during the pullet phase, laying phase, or the interaction for pullets with laying phases averaged over 11 (drinking) or 6 (eating) ages of the hens from 19 to 69 wk of age. 2 Control-control chickens never had access to perches during their life cycle; control-perch chickens had access to perches only during the egglaying phase of the life cycle (17 to 71 wk of age); perch-control chickens had access to perches only during the pullet phase (0 to 16.9 wk of age); and perch-perch chickens always had access to perches (0 to 71 wk of age). Figure 2. The proportion of caged White Leghorn hens reclining (a) or standing (b) on the rear perch during scotophase and photophase from 19 to 69 wk of age as taken by infrared cameras. *Asterisks at specific ages indicate a difference in daytime and nighttime perching activities (photoperiod age interaction, P < ). Values ± SEM represent the least squares means averaged over the pullet treatment of perch presence or absence. Perching. Night-time perching was more popular among hens as compared with perching during the day (x for rear perch = 44.6 vs. 11.3%, respectively, SEM = 1.1, P < ). More hens reclined (Figure 2a) or at some ages stood on the rear perch (Figure 2b) during scotophase as compared with photophase. The proportion of hens reclining on the rear perch was always greater during scotophase as compared with photophase (Figure 2a, P < ). In contrast, the proportion of hens standing on the rear perch did not differ at 19, 24, 29, 44, 49, 54, 64, and 69 wk of age between scotophase and photophase (Figure 2b), resulting in a photoperiod age interaction (P < ). Nighttime perching activity of the rear (Figure 3b) but not the front perch (Figure 3a) was influenced by the early access to pullet perches (pullet perch treatment age interaction, P < 0.02). Hens with prior perch experience as pullets used the adult rear perch less at night (specifically at 19, 34, 54, and 69 wk of age, Figure 3b) than hens that never had access to perches as pullets (Table 3, P = 0.04). When data were

5 BEHAVIOR OF CAGED HENS WITH PERCHES 2427 Table 3. The effect of perch access as pullets on adult perching behavior during scotophase as taken by infrared cameras Laying hen behavior during scotophase Item front perch rear perch both perches No perch experience as pullets 1 (%) a 92.3 Perch experience as pullets 1 (%) b 85.7 SEM n P-value a,b Least squares means within a column lacking common superscript differ (P < 0.05). 1 The pullet phase was from hatch to 16.9 wk of age. 2 Average number of observations per least squares means were averaged over 11 ages of the hens from 19 to 69 wk of age. combined on night time use of both the front and rear perches, differences between adult hens with and without pullet perches dissipated (Table 3, P = 0.12). Figure 3. The proportion of adult caged White Leghorn hens using the front (a) and rear (b) perches during scotophase from 19 to 69 wk of age as taken by infrared cameras. *Asterisks at 19, 34, 54, and 69 wk of age for the rear perch indicate differences between adult perching activity due to prior pullet perching experience (treatment age interaction, P < 0.02). Values ± SEM represent the least squares means. Over a 24-h period, more hens reclined rather than stood on the rear perch (Table 4). The proportion of hens standing on the rear perch was not influenced by prior experience with a pullet perch (P = 0.37), but reclining on the rear perch was affected by the pullet perch treatment. Specifically, if hens had exposure to perches as pullets, there was a lower proportion of them reclining on the rear perch as compared with hens that had no prior exposure to pullet perches (arcsine square root transformation, P = 0.03 as compared with P = 0.06 for untransformed data). Combining the data for both standing and reclining on the rear perch over a 24-h period showed similar trends to those reclining. In particular, the proportion of laying hens using the rear perch was less for adults that had access to perches as pullets as compared with hens without pullet perches at 34, 54, 64, and 69 wk of age (pullet perch treatment age interaction, P = 0.03, Figure 4). Behavior Recorded by an Observer in the Room Where the Hens Were Housed During Photophase For each behavior measured, the adult hens responded to the pullet perch treatment in the same manner as they aged, resulting in a nonsignificant age treatment interaction (P > 0.05). Front Perch Use. Laying hens with prior experience with pullet perches did not differ from those that did not have perches as pullets for the proportion of caged hens using the front perch as adults (Table 5, P = 0.14). There were no interactions between the pullet perch treatment and the time of the day that observations were made (morning vs. afternoon, P > 0.05). However, use of the front perch was more popular in the morning than the afternoon (x = 4.1 vs. 2.0%, respectively, SEM = 0.2, P < ). Rear Perch Use. Unlike the front perch (Table 5, P = 0.14), adult use of the rear perch was influenced by earlier experience with pullet perches. Adults that had prior experience with perches as pullets used the rear perch less than control adults with no prior experience

6 2428 Hester et al. Table 4. The effect of perch access as pullets on adult perching behavior as taken by infrared cameras Item Hens standing on rear perch Laying hen behavior during both photophase and scotophase Hens reclining on rear perch Hens standing and reclining on rear perch No perch experience as pullets 1 (%) a 30.0 a Perch experience as pullets 1 (%) b 25.8 b SEM n P-value a,b Least squares means within a column lacking common superscript differ (P < 0.05). 1 The pullet phase was from hatch to 16.9 wk of age. 2 Average number of observations per least squares means averaged over 11 ages of the hens from 19 to 69 wk of age and over 2 photoperiods (photophase and scotophase). with perches (Table 5, P = 0.006). It was specifically the morning use of the rear perch that was less for hens that had earlier experiences with pullet perches as compared with adults with no prior pullet perch experience (Figure 5a). Perching activity during afternoon observations did not differ between adult hens with or without prior experience with pullet perches (pullet treatment time of day interaction, P = 0.03, Figure 5a). Similar to the front perch, use of the rear perch was more popular in the morning than the afternoon (x = 14.7 vs. 8.5%, respectively, SEM = 0.6, P < ). Use of Both Front and Rear Perches. Collectively, the proportion of hens using both perches was influenced by prior experiences with pullet perches. As with the rear perch, the proportion of hens using both perches was less for those adults with prior access to pullet perches as compared with laying hens with no prior experience with pullet perches (Table 5, P = 0.007). Figure 4. The proportion of adult caged White Leghorn hens using the rear perch from 19 to 69 wk of age as taken by infrared cameras. Usage includes both standing as well as reclining hens on the rear perch over a 24-h period. *Asterisks at 34, 54, 64, and 69 wk of age for rear perch use indicate differences between adult perching activity due to prior experience with pullet perches (pullet perch treatment age interaction, P < 0.03). Values ± SEM represent the least squares means averaged over a 24-h observation period. The morning, not the afternoon, perching differed between pullet perch treatments. Specifically, a lower proportion of hens with prior perching experience as pullets used both perches as compared with adult hens that did not have access to perches as pullets (Figure 5b, treatment time of day observation, P = 0.03). Not unexpectedly because of the similarity of results to use of front or back perches, use of both perches by hens was more popular in the morning than the afternoon (x = 18.8 vs. 10.5%, respectively, SEM = 0.7, P < ). Hens Lying on the Cage Floor. Experience with pullet perches did not affect the proportion of caged hens lying on the cage floor (Table 5, P = 0.78). There was no interaction between the pullet perch treatment and the time of the day when observations were made (morning vs. afternoon, P > 0.05). However, lying on the cage floor was more popular in the morning than the afternoon (x = 10.2 vs. 2.9%, respectively, SEM = 0.3, P < ). DISCUSSION Hens use perches at night to rest and sleep (see review of Hester, 2014). Nighttime use of perches in cages in the current study averaged 89% with equal use of front (44.6%) and back (44.5%) perches (Table 3). Daytime use averaged 14.7% with the rear perch (x = 11.6%) preferred over the front perch (x = 3.1%, Table 5) perhaps because hens were seeking refuge from the presence of humans in the room or the feeding activity of other hens, which were in close proximity to the front perch. More human activity occurred at the front of the cage as compared with the back of the cage because the cage front was where the hens were fed and the eggs were collected. Animal caretakers also walked the back aisle behind the cages to check drinkers, but this activity did not take as long as feeding and egg collection. Previous studies reported 85 to 100% of the hens perching during the night, which is similar to our study, whereas previous reports on daytime use ranged from 25 to 30% in furnished cages (Tauson, 1984; Duncan et al., 1992; Tauson and Abrahamsson, 1994; Abrahams-

7 BEHAVIOR OF CAGED HENS WITH PERCHES 2429 Table 5. The effect of perch access as pullets on adult perching behavior as recorded by an observer in the room where the hens were housed Laying hen behavior during photophase Item front perch rear perch both perches Hens lying on the cage floor No perch experience as pullets 1 (%) a 16.4 a 6.6 Perch experience as pullets 1 (%) b 13.0 b 6.3 SEM n P-value a,b Least squares means within a column lacking common superscript differ (P < 0.05). 1 The pullet phase was from hatch to 16.9 wk of age. 2 Average number of observations per least squares means averaged over 11 ages of the hens from 25 to 68 wk of age and over 2 times of observations (morning and afternoon). son et al., 1996; Appleby et al., 2002), which is twice the daytime usage reported in the current study. Differences in stocking density, the strain of hens used, cage arrangement such as number of tiers, light intensity, and amenities such as a nest may have contributed to the differences between this study and other studies on daytime perch use. Nevertheless, lower usage of perches in cages during the day is expected because hens are more active during photophase, spending less time sleeping. Hens of the current study spent a considerable proportion of their time during photophase eating Figure 5. The proportion of adult caged hens using the rear perch (a, SEM = 0.9) or both perches (b, SEM = 1.0) during photophase as recorded by an observer in the room where the hens were housed. Differences in adult perching activity due to pullet perch treatment and the time of the day that the observations were made are indicated by uncommon letters (a c; treatment time of day, P = 0.03 for both the rear perch use and total perch use). Values represent the least squares means averaged over the age of the hens. (20%) and drinking (4%, Table 2) with hardly any hens eating and drinking at night. Hens given early access to perches as pullets did not result in greater use of the adult perch. In contrast to our hypothesis, a greater proportion of hens that had perches as pullets used the rear perch of the laying cage less during both nighttime (Table 3) and daytime (Table 5) perching than hens without prior pullet perching experience. This heavier use of the rear perch by adult hens without prior perching experience was evident as early as 19 wk of age (Figure 3b), just 2 wk after placement of hens in laying cages and persisted to the end of lay (Figure 4). Perches allow hens to minimize interaction with feather peckers and aggressive hens (Tauson, 1984; Duncan et al., 1992). Although we have no recorded incidence of aggressiveness and feather pecking in the current study, hens without prior pullet perch experience may have felt more compelled to use the adult perches to avoid these unpleasant encounters than hens already acclimated to perches because of their earlier exposure, which would explain the greater usage on a proportional basis. Another possibility is that the novelty of the perches had worn off by hens that had access to perches as pullets. Animals can habituate to and stop using enrichment devices (Mench, 1994). For example, the number of pecks made to a string provided intermittingly to Lohmann Brown chickens decreased from a high of 14.1 at 3 d to 4 at 14 wk, and to 0 at 26 wk of age (Jones et al., 2000). However, as previously discussed, perches were used heavily in the current study, especially at night, so habituation is unlikely as a cause for less usage. Perches also provide opportunity for hens to reduce bird density on the cage floor, offering a reprieve from standing on a sloped, wired cage floor (Appleby et al., 1992; Tauson and Abrahamsson, 1996; Abrahamsson and Tauson, 1997). The increase proportional use of the adult perch may have been an effort by hens that did not have access to pullet perches to relieve pressure on their foot pad, though foot health was excellent throughout the study with no differences due to perch presence or absence during either the pullet (Enneking et al., 2012a) or laying phases (Hester et

8 2430 Hester et al. al., 2013b). Differences in keel deformities and fracture incidences would also not explain the higher perch usage by naive hens as these bone health indicators at 71 wk of age were similar in hens that had prior experience with pullet perches as compared with those with no pullet perch access (Hester et al., 2013a). In addition, there were also no keel fractures and deformities in any of the excised sternums examined in 12-wk-old pullets with or without access to perches (Enneking et al., 2012a). In companion papers of this study, use of perches as pullets increased muscle deposition (Enneking et al., 2012a) and use of adult perches increased bone mineral density (Hester et al., 2013a) when measurements were made at 12 and 71 wk of age, respectively. However, assessment of bone mineralization in 71-wk-old hens showed that whereas the adult perching activity increased bone mineralization, the earlier pullet perching activity did not culminate in improved bone mineralization. The fact that adults with prior pullet perching experience used the rear perch less during both scotophase and photophase perhaps contributed to the loss of a pullet perching effect on skeletal mineralization when measured at end of lay at 71 wk of age. Eating and drinking activities of caged adult Leghorns were not impaired by their prior experience to perches as pullets or by the presence of perches in laying cages. In fact, during photophase, the presence of adult perches in the laying cage actually resulted in a greater proportion of hens eating as compared with hens that did not have perches in laying cages (Table 2). These hens with access to perches that displayed increased proportions of feeding activity actually had lower BW at 71 wk of age as compared with hens without perches. The increased exercise associated with stepping onto and off the perch stimulated feeding activity, and kept hens better fit with reduced relative fat pad weights as compared with controls with no perches at 71 wk of age (Jiang et al., 2014). The increase in feeding activity of hens with perches as compared with the proportion without perches did not result in increased feed utilization (consumption plus any feed wastage) when assessed at 11 different ages from 18 to 68 wk of age and also did not result in an increase in egg production (Hester et al., 2013b). Because 71-wk-old hens with access to perches had less abdominal fat when expressed relative to BW, their maintenance needs may have been less than the heavier control hens without perches. Less maintenance needs would require less feed, whereas increased activity could stimulate appetite resulting in these effects cancelling each other out, resulting in similar usage of feed. Another possibility is that the exercise associated with perching caused hens to spend more time at the feeder, but the quantity of food swallowed per ingestion could have been less than the amount consumed by control hens without perches. The shift in behavior during scotophase at 34 (June 8, 2011) and 39 (July 11, 2011) wk of age with a lower proportion of hens reclining (Figure 2a) and a greater proportion of hens standing (Figure 2b) on the rear perch was most likely due to extremely hot weather during those 2 d of behavioral observations. With a greater proportion of the hens standing on the rear perch at night, the hens were more likely to release body heat to the surrounding air than if the hens had remained in reclined position. In conclusion, eating and drinking activities of caged adult Leghorns were not impaired by their prior experience to perches as pullets or by the presence of perches in laying cages. Providing perches in cages to White Leghorns during pullet rearing did not facilitate use of perches as adults. Instead, White Leghorns with no prior experience with pullet perches used adult perches more than their experienced counterparts throughout egg laying. Some possibilities for increased usage by hens with no prior experience with pullet perches is that they felt safer and less fearful, the perches were more novel, or they relieved pressure on their foot pads as compared with hens that did have perches as pullets. The implications are that cage rearing of pullets does not require perches to encourage adult perching in laying cages. ACKNOWLEDGMENTS Support for this project was provided by Agriculture and Food Research Initiative competitive grant no from the USDA National Institute of Food and Agriculture (Washington, DC). Appreciation is extended to F. A. Haan and B. D. Little of Purdue University in West Lafayette, Indiana, for the care and management of the chickens. T. L. Pollard of Big Dutchman donated the perches used in the study (Holland, MI). Chicks were donated by Hy-Line Hatchery (Warren, IN). REFERENCES Abrahamsson, P., and R. Tauson Effects of group size on performance, health and birds use of facilities in furnished cages for laying hens. Acta Agric. Scand. A 47: Abrahamsson, P., R. Tauson, and M. C. Appleby Behaviour, health and integument of four hybrids of laying hens in modified and conventional cages. Br. Poult. Sci. 37: Appleby, M. C., and I. J. H. Duncan Development of perching in hens. Biol. Behav. 14: Appleby, M. C., S. F. Smith, and B. O. Hughes Individual perching behaviour of laying hens and its effects in cages. Br. Poult. Sci. 33: Appleby, M. C., A. W. Walker, C. J. Nichol, A. C. Lindberg, R. Freire, B. O. Hughes, and H. A. Elson Development of furnished cages for laying hens. Br. Poult. Sci. 43: Duncan, E. T., M. C. Appleby, and B. O. Hughes Effect of perches in laying cages on welfare and production of hens. Br. Poult. Sci. 33: Enneking, S. A., H. W. Cheng, K. Y. Jefferson-Moore, M. E. Einstein, D. A. Rubin, and P. Y. Hester. 2012a. Early access to perches in caged White Leghorn pullets. Poult. Sci. 91: Enneking, S. A., P. S. Wakenell, J. P. Garner, and P. Y. Hester. 2012b. Mortality and behavior of caged White Leghorn pullets with access to perches. CD Paper in Proc. XXIV World s Poult. Congr., Salvador, Brazil. World s Poult. Sci. J. Suppl. 1:

9 BEHAVIOR OF CAGED HENS WITH PERCHES 2431 Gunnarsson, S., L. J. Keeling, and J. Svedberg Effect of rearing factors on the prevalence of floor eggs, cloacal cannibalism and feather pecking in commercial flocks of loose housed laying hens. Br. Poult. Sci. 40: Hester, P. Y The effect of perches installed in cages on laying hens. World s Poult. Sci. J. 70: Hester, P. Y., S. A. Enneking, B. K. Haley, M. E. Einstein, H. W. Cheng, and D. A. Rubin. 2013a. The effect of perch availability during pullet rearing and egg laying on musculoskeletal health of caged White Leghorn hens. Poult. Sci. 92: Hester, P. Y., S. A. Enneking, K. Y. Jefferson-Moore, M. E. Einstein, H. W. Cheng, and D. A. Rubin. 2013b. The effect of perches in cages during pullet rearing and egg laying on White Leghorn hen performance, foot health, and plumage. Poult. Sci. 92: Hy-Line International Hy-Line Variety W-36 Commercial Management Guide. Hy-Line International, West Des Moines, IA. Jiang, S., P. Y. Hester, J. Y. Hu, F. F. Yan, R. Dennis, and H. W. Cheng Effects of perches on liver health of hens. Poult. Sci. 93: Jones, R. B., N. L. Carmichael, and E. Rayner Pecking preferences and pre-dispositions in domestic chicks: Implications for the development of environmental enrichment devices. Appl. Anim. Behav. Sci. 69: Lambe, N. R., and G. B. Scott Perching behaviour and preferences for different perch designs among laying hens. Anim. Welf. 7: Mench, J. A Environmental enrichment and exploration. Lab. Anim. 23: NRC Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC. Oehlert, G. W Comparing models: The analysis of variance. Pages in A First Course in Design and Analysis of Experiments. W. H. Freeman and Co., New York, NY. Olsson, I. A., and L. J. Keeling The push-door for measuring motivation in hens: Laying hens are motivated to perch at night. Anim. Welf. 11: SAS Institute SAS Proprietary Software. Version 9.2. SAS Inst. Inc., Cary, NC. Steel, R. G. D., J. H. Torrie, and D. A. Dickey Principles and Procedures of Statistics: A Biometrical Approach. 3rd ed. McGraw Hill Book Co., New York, NY. Tauson, R Effects of a perch in conventional cages for laying hens. Acta Agric. Scand. 34: Tauson, R., and P. Abrahamsson Foot and skeletal disorders in laying hens. Effects of perch design, hybrid, housing system and stocking density. Acta Agric. Scand. A 44: Tauson, R., and P. Abrahamsson Foot and keel bone disorders in laying hens. Effects of artificial perch material and hybrid. Acta Agric. Scand. A 46: Winer, B. J Statistical Principles in Experimental Design, 2nd ed. McGraw-Hill Inc., New York, NY.