1. The Effect of Perches on the Behavior of Caged
White Leghorn Pullets
Jourdan Ringenberg
1

2. INTRODUCTION
Approximately 90% of developed countries utilize conventional cages for egg-laying hens
(Tauson, 1998). Conventional cages are more economically efficient, reduce the frequency of
cannibalism, and decrease the ammonia and dust levels in the air that can cause respiratory
problems (Tauson, 1998; Lay et al., 2011). Despite these advantages, conventional cages have
been criticized for reducing hens' abilities to express natural behavior and also increasing risk of
osteoporosis due to lack of mobility (Sandilands et al., 2009). Over the past two decades, much
research has focused on finding different alternatives to conventional cages for egg-laying hens.
One alternative to conventional cages is enriching cages with perches. The space available in
a conventional cage does not allow for furnishments or expression of natural behavior. Perching
is a highly motivated behavior in hens allowing them to escape unwanted attention from other
birds in a non-cage system and also allowing for roosting at night (Sandilands et al., 2009). The
motivation of 2 groups of hens to utilize an aerial perch or a placebo perch (birds could not
perch) at night showed that birds were more motivated to reach the aerial perch (Olsson and
Keeling, 2002). When a hen perches, a tendon-locking reflex occurs that requires little energy or
muscle exertion and is triggered when the bird flexes its leg muscles underneath it as it lands
causing the phalanges to shorten and curl around the perch (Sandilands et al., 2009).
Small space allotment per hen limits mobility which can lead to osteoporosis and subsequent
bone breakage. Osteoporosis is a bone disease marked by progressive structural bone loss which
increases the bone's fragility and makes it more susceptible to fractures (Whitehead and Fleming,
2000). It is a widespread problem that contributes to approximately 20 to 35% mortality in cage
layer hens (Anderson, 2002). While osteoporosis in laying hens is caused by genetics, the small
cage size limits opportunity for exercise and may also be a factor (Whitehead and Fleming,
2

3. 2000). While the addition of perches has been shown to increase bone strength, there is also an
increase in old fractures, especially with aerial perches in extensive systems (Sandilands et al.,
2009).
The purpose of this study was to determine if exposure to perches in cages during the
prepubescent stage will lead to improvement in bone strength and a reduction in bone fractures.
Past research has focused on enriching cages after puberty with minimal research conducted
during the pullet phase (Duncan et.al., 1992; Barnett et.al., 2009). Studies in humans have shown
that pre-pubertal exercise reduces the risk of osteoporotic fractures in adults (Bass et al., 1998). It
is therefore feasible that perhaps pullet perch mobility will prevent adult bone fractures.
MATERIALS AND METHODS
White Leghorn females, 1,064 in total, of the Hy-Line W36 strain were transported from the
Hy-Line hatchery in Warren, IN to the Purdue University Poultry Research Farm. Each chick
was wing banded in the right wing with a metal band and randomly assigned to 1 of 28 pullet
cages, resulting in 38 chicks/cage. The treatments, perch and control, were assigned to each of
the 28 pullet cages in the Grower Research Unit room using restricted randomization so that
equal numbers of treatments were assigned to each of the 2 sides of the room. There were 2 rows
of cages for each side of the room for a total of 4 rows.
Chicks assigned to a cage were group weighed prior to placement. The BW were also
determined individually at 3, 6, and 12 wk of age. Water was provided by 2 drip nipple
drinkers/cage. Pullets were fed starter (hatch to 3.9 wk) and grower (4 to 17 wk) diets that met or
exceeded the requirements of the Hy-Line W36 management guide (2009-2011). Room brooding
temperature was maintained at 32 to 33º C the first week of the chick's life. Temperature was
3

4. reduced 1 to 3º C per week until a temperature of 21º C was reached which was maintained for
the remainder of the study. Mortality was recorded on a daily basis.
Light regimen was determined by the length of photoperiod necessary for the age of the birds.
Chicks were exposed to a L:D photoperiod of 22:2 during the first wk of age at an intensity of 33
lux. Beginning at 1 wk of age, the L:D photoperiod changed to 20:4 at a light intensity of 6 lux.
Each subsequent week represented a 1 h decrease in light hours. At 9 wk the L:D photoperiod
reached 12:12 and was maintained through 17 wk.
To allocate more space for each bird as it grew, pullets were removed from the cages at
predetermined ages. Table 1 below shows the floor space allocation per bird, perch space/bird,
and feeder space/bird for the grower phase.
Table 1. Grower cage specifications1
Age of bird Birds/cage
Floor space
Perch
space/bird
Feeder
space/bird
____
wk ____ _
cm2
/bird (in2
/bird) _ _
cm (in) _ ___
cm (in) ___
0 38 98 (15) 3.2 (1.3) 1.6 (0.6)
3 28 133 (21) 4.4 (1.7) 2.2 (0.9)
3.4 27 138 (21) 4.5 (1.8) 2.3 (0.9)
4.4 24 155 (24) 5.1 (2.0) 2.5 (1.0)
6 16 233 (36) 7.6 (3.0) 3.8 (1.5)
12 12 310 (48) 10.2 (4.0) 5.1 (2.0)
1
Pullets were housed in grower cages from 0 to 17 wk of age
Conventional cages were retrofitted with two Big Dutchman perches (Figure 1), whereas the
control cages contained no perches. Each perch sat 8.9 cm from the cage floor, with an 18 cm
4

5. distance between the front and rear perch. An 18 cm distance also existed between the front
perch and the feeders and between the rear perch and the back of the cage. Each perch had a
diameter of 32 mm.
Figure 1. Perch placement and dimensions for a perch treatment cage.
Behavior was recorded at 10 ages every 2 wk from 2 to 16 wk of age using 14 Stealth Cam
STC-I540IR automatic digital cameras (Cabela’s Inc., Sidney, NE). Additional recordings were
done at 5 and 15 wk of age. At each age cameras recorded behavior of each cage of the top row
on both sides of the room on day 1 and the lower row of both sides of the room on day 2.
Behavioral observations were conducted for 24 h and initiated at approximately 13:00 h. Two
pictures, taken within a few seconds of one another, were made at 5 min intervals if activity was
occurring within the cage. A second picture was taken immediately after the first picture. If there
were no movements in the cages, then no pictures were taken providing opportunity to assess
activity level. Behavior was recorded from the first picture. The second picture was used only if
it was difficult to determine behavior from the first picture.
Behaviors recorded prior to 6 wk of age included the number of chickens in each cage
that were drinking. The numbers of chicks perching on the front and back perch and whether the
5
61 cm (24 in)
61 cm (24 in)
46 cm (18 in)
8.9 cm (3.5 in)

6. bird was sitting or standing on the perch were recorded for those cages assigned the perch
treatment (see ethogram in Table 2). The proportions of chickens that were eating were
determined from 2 to 16 wk of age. The number of birds performing each behavior was recorded
regardless of time of day.
The types of behaviors recorded from 6 to 16 wk of age were dependent upon time of day
(Table 3). Drinking and front perching were recorded as either yes (1) or no (0). Because the
stocking densities used in the current study were similar to industry standards, it was difficult to
count the number of pullets performing specific behaviors; therefore, a yes or no recording was
used under these circumstances. Lower activity at night when the lights were turned off allowed
for accurate recording of the number of birds using the front perch. However, drinking and rear
perching were more difficult to discern during dark hours and these behaviors were recorded as
either yes or no. There were some observations where eating, drinking, and perching behavior
could not be accurately determined, and they were identified as not available (NA).
Table 2. The ethogram used for chicks at 2, 4, and 5 wk of age
Behavior Definition
Eating 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 the feed) count as eating.
Front perch
sit
Both of the bird's feet are on the front perch and its chest is resting
on the perch because it is lowered all the way down to sit on it.
The head can be tucked down or extended up.
Front perch
stand
Both feet are on the front perch and chest is NOT resting on the
perch. It may be standing straight up or crouched down, as long as
its chest is off the perch. If unsure of a bird's posture, classify as
"stand".
Rear perch
sit
Both of the bird's feet are on the rear perch and its chest is resting
on the perch because it is lowered all the way down to sit on it.
The head can be tucked down or extended up.
6

7. Rear perch
stand
Both feet are on the front perch and chest is NOT resting on the
perch. It may be standing straight up or crouched down, as long as
its chest is off the perch. If unsure of a bird's posture, classify as
"stand".
Drinking Bird's beak is either in contact w/ the tip of the drinker and/or w/in
the defined 'zone' of the drinker. The 'zone' being approximately
the size of one cage square around the drinker tip.
Table 3. The ethogram used for chicks at 6, 8, 10, 12, 14, 15, and 16 wk of age.
Behavior Definition
Eating 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 the feed) count as eating.
Drinking
1/0
Includes both drinkers. If a bird(s) is drinking, input "1." If no
birds are drinking, input "0."
Front perch
1/0
Use during light hours. If a bird(s) is perching, input "1." If no
birds are perching, input "0." If you can see that a bird has only 1
foot on the perch then it's not perching.
Rear perch
1/0
Use during dark hours - If a bird(s) is perching, input "1." If no
birds are perching, input "0." If you can see that a bird has only 1
foot on the perch then it's not perching.
Eating
NA1
You can't see into the feeder to determine the number of birds
eating.
Rear perch
NA
Use during dark hours - You don't see any birds on the perch, but
the view of the perch is partially blocked so you can't determine if
any birds are perching or not.
Drinking
NA
You don't see any birds drinking, but the view of one or both
drinkers is blocked so you can't determine if birds are drinking.
Front perch
NA
You don't see any birds on the perch, but the view of the perch is
partially blocked so you can't determine if any birds are perching
or not.
Front perch
PM
Use during dark hours - The bird is off the ground and on the front
perch. If you can see that a bird has only 1 foot on the perch then
it's not perching.
1
NA = not available.
Behavioral data were analyzed using ANOVA. Percentage data were transformed either to
logs or squared. Perch treatment, age of the pullets, and time of day (photophase vs scotophase)
were considered fixed effects. Age of the pullets was used as a split plot or repeated measure
7

8. when perch treatment was included in the model (Steel et al., 1997). The Tukey-Kramer test or
the SLICE option (Winer, 1971) was used to partition differences among means (Oehlert, 2000).
The analysis was conducted using the mixed model procedure of SAS (2008).
RESULTS
Mortality from hatch to 3 wk of age increased in cages with perches as compared to controls
(P < 0.0001, Table 4). Mortalities during the first 3 wk were due to omphalitis and starve-outs.
After 3 wk of age until the end of the study at 17 wk of age, there were 3 additional deaths due
to splayed legs (n =2 for the perch treatment) or E. coli infection (control treatment, data not
presented in a table).
Table 4. The effect of perches installed in conventional cages on early mortality
Causes of mortality
Treatment
Mortality
0 to 3 wk of age1
Omphalitis
Starve-
outs Enteritis
Slipped
gastrocnemius
tendon Other
____
% ____ _____________________
% of total mortality _____________________
Perch 7.0 ± 0.8a
34.1 29.5 6.8 6.8 4.52
Control 1.5 ± 0.8b
9.1 4.5 2.3 0 2.33
a-b
Means within a column with no common superscript are different (P < 0.05).
1
n= 14 observations per least square mean.
2
Other cause of mortality was dehydration.
3
Other cause of mortality was that the chick was crushed.
The proportion of chicks drinking (log values) was lower during scotophase (-9.942 ± 0.4267)
than photophase (0.644 ± 0.0426, P < 0.0001). Drinking activity was greater for pullets in cages
with perches at 2 wk and less at 4 and 5 wk of age when compared to controls without access to
perches resulting in a treatment x age interaction (P = 0.05, Figure 2).
8

9. Figure 2. The proportion of pullets drinking with and without (control) access to perches at 2, 4,
and 5 wk of age. Values represent the least square means of log transformations ± SEM.
A greater proportion of pullets ate during photophase than scotophase (P < 0.0001). During
night or scotophase, a greater proportion of chicks with access to perches were eating at 2 wk of
age as compared to controls, while the opposite occurred at older ages. Specifically, at 6, 10, 12,
14, 15, and 16 wk of age, a greater proportion of control pullets were eating as compared to
chicks with access to perches (Figure 3).
9

10. Figure 3. The proportion of pullets eating during scotophase with and without (control) access to
perches from 2 to 16 wk of age. Values represent the least square means of log transformations ±
SEM. Within an age, the asterisk (*) indicates significant difference between means at a P < 0.05.
Unlike scotophase (Figure 3), the proportion of chicks eating during photophase did not differ
between chickens with and without perches resulting in a treatment x age x time of day
interaction (Figure 4, P = 0.0002).
10

11. Figure 4. The proportion of pullets eating during photophase with and without access to
perches from 2 to 16 wk of age. Values represent the least square means of log
transformations ± SEM.
Pullets with access to perches had activity levels similar to controls (square transformation of
% activity = 6719 ± 140 and 7048 ± 140, respectively, P = 0.1086). As pullets aged, the
proportion of pullets active during scotophase increased up to 10 wk of age after which no
further increases were noted to 16 wk of age. During photophase, the level of activity changed
little with age (time of day x age interaction, P < 0.0001).
11

12. Figure 5. The activity level of pullets with and without access to perches from 2 to 16 wk of age.
Values represent the least square means of squared transformations ± SEM. a-f
Means within
either scotophase or photophase with no common superscript are different (P < 0.05).
There were no differences in BW at 3 and 6 wk of age; however, at 12 wk of age, the BW
increased for pullets with access to perches (P = 0.025, Figure 6).
Figure 6. The body weight of pullets with and without access to perches at 3, 6, and 12 wk of
age. Values represent the least square means ± SEM. a-b
Means at 12 wk of age with no common
superscript are different (P < 0.05).
12

13. During scotophase, the proportion of chicks using the front perch increased from 6 to 12
wk of age after which no further increases were noted to 16 wk of age (P < 0.0001, Figure 7).
Figure 7. The proportion of pullets using the front perch during scotophase from 6 to 16 wk of
age. Values represent the least square means of log transformations ± SEM. a-d
Means with no
common superscript are different (P < 0.05).
DISCUSSION
It is unknown why pullets assigned to the perch treatment had higher mortality than controls.
Omphalitis and starve-outs were the main causes of the early mortality with the infectious agent
most likely hatchery derived. Since the round metal perches were new and had never been used
before, it is doubtful that they were the source of infection or that they were harboring infectious
agents. Chicks were assigned randomly to cages with hatchling BW similar between treatments
(perch treatment: 39.2 ± 0.14 g; controls: 39.0 ± 0.14 g, P = 0.41). The high mortality of chicks
with access to perches from 0 to 3 wk of age was not due to lack of drinking or eating. At 2 wk
of age, the higher proportion of chicks drinking and eating (scotophase only) in the perch
13

14. treatment as compared to controls suggests that the presence of perches in cages did not
contribute to dehydration and emaciation. Because of the higher early mortality and fewer chicks
in the cages with perches, there was less competition for resources (feeders and drinkers) at 2 wk
of age which could have contributed to the increased drinking and eating behaviors noted at that
age. Bird numbers were adjusted at 3 wk of age (Table 1, 28 chicks/cage or 133 cm2
of cage floor
space /pullet) resulting in comparable stocking densities among cages for the remainder of the
pullet study. The similar BW of pullets with and without access to perches at 3 wk of age also
suggests that the presences of perches in cages did not interfere with drinking and eating
behaviors.
The greater BW of chicks with access to perches at 12 wk of age cannot be explained through
increased eating activity because there was no difference in the proportion of pullets eating
during photophase when the majority of this behavior occurred. The increase in the proportion of
chicks of the perch treatment eating at 2 wk of age during scotophase was inconsequential due to
its low incidence. Furthermore, this trend in eating among pullets with access to perches did not
persist as it was the controls who showed more eating at 6 wk of age and older. The greater BW
of chicks in the perch treatment also cannot be explained by the proportion of pullets that were
active as this behavior did not differ between pullets with and without access to perches. The
increased use of perches at night could have contributed to the increase in 12 wk-old BW as
pullets with access to perches had larger bone size and leg muscle weight as compared to
controls (Moss et al., 2012).
Increased perching activity at night as the pullets age could be due to two factors. One being,
as pullets grow in size with age, they may be more likely to jump and/or fly to the height of the
perch. Secondly, the 12 wk period where pullets increased perching activity may be the time it
14

15. takes for them all to learn what the perch is and how to use it, as they were not initially taught as
part of the experiment.
Future research should focus on teaching chicks how to perch at an earlier age to encourage
its use and promote exercise. It is a common management practice in industry to show a few
chicks within each cage the location of the drinkers during placement to encourage drinking.
Other chicks learn drinking behavior from those that were shown the drinkers. At the same time
that chicks are shown drinkers, they could also be placed on the perch. Showing chicks during
placement how to perch may teach them to perch at a younger age and subsequently improve
long-term skeletal health.
ACKNOWLEDGEMENTS
Appreciation is extended to Mark Einstein for his statistical advice.
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