The Effect of Perches on the Behavior of Caged

White Leghorn Pullets

Jourdan Ringenberg

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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,

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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

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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/birdFeeder

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)

1Pullets 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

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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

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61 cm (24 in)

61 cm (24 in)

46 cm (18 in)

8.9 cm (3.5 in)

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.

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The head can be tucked down or extended up.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 DefinitionEating 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.

Drinking1/0

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.

EatingNA1

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.

1NA = 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

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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

TreatmentMortality

0 to 3 wk of age1Omphalitis 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-bMeans within a column with no common superscript are different (P < 0.05). 1n= 14 observations per least square mean.2Other cause of mortality was dehydration.3Other 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).

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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).

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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).

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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).

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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-fMeans 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-bMeans at 12 wk of age with no common

superscript are different (P < 0.05).

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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-dMeans 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

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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

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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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