Group Selection for Adaptation to Multiple-Hen Cages:
Production Traits During Heat and Cold Exposures1,2
PATRICIA Y. HESTER, W. M. MUIR, J. V. CRAIG, and J. L. ALBRIGHT
Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907
ABSTRACT
A selected line of White Leghorns that
has shown improved survivability and productivity and
reduced feather loss in multiple-hen cages was evaluated for production traits under both stressed and
unstressed conditions. It was hypothesized that hens
selected for adaptation to multiple-bird cages would
react less intensely to stressors and therefore lay more
eggs and have lower mortality under stressed conditions. Three lines of chickens (selected, control, and
commercial) were housed in either single-hen (1 hen) or
multiple-hen cages (12 hens, social competition) at 16.7
or 17.1 wk of age. They were subsequently subjected to
cold exposure at 33 wk of age and heat exposure at 44
wk of age.
The selected line of chickens in multiple-hen cages
showed an increased resistance to heat exposure, as
indicated by lower mortality, when compared to the
control and commercial lines housed in multiple-hen
cages. Egg production 8 d prior to, during, and 8 d
following either cold or heat exposures indicated that
the selected line of chickens withstood social, handling,
and environmental stressors better than the control line
and, in some cases, the commercial line of chickens. It
was concluded that the selected line of Leghorns
showed evidence of stress resistance through lowered
mortality and improved production.
{Key words: selection, adaptation, multiple-hen cages, Leghorns, production)
1996 Poultry Science 75:1308-1314
INTRODUCTION
Not all strains of White Leghorns respond equally to
a multiple-bird environment. For example, Cunningham
and Ostrander (1982) compared two commercial strains
of White Leghorns for responses to multiple bird cages.
Fearfulness did not differ between the two strains, and
both strains showed decreased feed usage per bird in
higher densities; however, the colony size for maximum
net profit differed between the strains. One strain
produced higher net income with five birds per cage,
whereas the other strain yielded higher income with
four birds per cage. A comparison of five White Leghorn
strains showed that the commercial strain with the least
severe and the lowest frequency of agonistic behavior
also demonstrated the highest survival percentage and
the best egg production (Choudary et ah, 1972). A later
study, however, showed no relationship between overt
agonistic behavior and productivity of White Leghorns
in multiple-hen cages (Al-Rawi et al., 1976). Other
researchers have demonstrated that lines differ in their
Received for publication November 6, 1995.
Accepted for publication July 1, 1996.
ijournal Article Number 14,861 of the Purdue University Agricultural Research Programs, West Lafayette, IN 47907.
financial support for this study was provided by USDA Award
Number 58-3602-3118.
adaptability to multiple-hen cages (Wilson et ah, 1967;
Choudary et al, 1972; Al-Rawi et al, 1976; Hansen, 1976;
Ouart and Adams, 1982a,b; Craig et al, 1983; Craig and
Lee, 1989, 1990).
Although it is common practice to house commercial
egg layers in multiple-hen cages, some primary breeders
often select breeding stock in single-bird cages because
measuring production in single-bird cages can maximize
individual responses to selection, as an optimum index
based on within- and between-family differences can be
utilized (Garwood and Lowe, 1981). However, selection
for improved individual performance may lead to a
decline in group performance, especially if the selected
traits also increase susceptibility to unfavorable environments (Griffing, 1967) and increase aggressiveness
among cage mates (Lowry and Abplanalp, 1972; Craig et
al, 1975; Bhagwat and Craig, 1977, 1978; Lee and Craig,
1981). White Leghorn strains that are high producers
under less competitive situations may not be the best
lines to house in multiple-hen cages. Group selection,
defined as selection of birds based on group rather than
individual performance, may be a more viable alternative for selecting caged breeder stock (Muir, 1996).
A selected line of White Leghorns was developed by
Muir (1996) that has shown improved survivability and
reduced feather loss in multiple-hen cages (Craig and
Muir, 1996). It was hypothesized that hens genetically
selected for adaptation to a multiple-bird environment
1308
PRODUCTION OF HENS ADAPTED TO MULTIPLE-HEN CAGES
should react less intensely to social competition, and
perhaps to all stressors in general, than the unselected
controls. To test this hypothesis, the physiological
response to social, thermal, and handling stress of
selected, unselected control, and a commercial Leghorn
line was evaluated (Hester et al., 1996). In many, but not
all, instances, the selected line reacted less intensely to
the stressors. Criteria for a less intensive response to
stress included hemodilution (decreased packed cell
volume) at the time of transfer to multiple hen cages and
the lack of a leucocytic response due to social competition at 33 wk of age. The objective of the present study
was to compare the production traits of a selected line of
chickens developed by Muir (1996) with an unselected
control line and a commercial line of Leghorns under
both stressed and unstressed conditions.
MATERIALS AND METHODS
Three genetic stocks of White Leghorns were compared. A line selected over seven generations for
survival and hen-day egg production in multiple-bird
cages was derived from and compared to an unselected
control line, the North Central Randombred Control.
The third stock was a commercial line of layers. The
three strains of chicks were hatched on June 16, 1993 at
the Purdue University Hatchery and reared in groups of
16, with others of their own strain and sex, in 61 x 91 cm
wire cages. During the entire experimental period, feed
and water were provided for ad libitum consumption.
Beak trimming was not performed. More details on the
origin of the genetic stocks, management of the birds,
and assignment of the three genetic lines of pullets with
respect to room, cage row within the room, and cage
size (single- vs multiple-hen) are described by Craig and
Muir (1996).
At 16.7 to 17.1 wk of age, chickens of the three genetic
lines were placed in either single-hen (1 pullet per cage,
providing 1,085 cm 2 per bird) or multiple-hen (12 pullets
per cage, which provided 362 cm 2 per bird) cages in one
of four independently heated, ventilated, and lighted
rooms of the Purdue University Layer Research Unit.
Any observed effects of single- vs multiple-bird cage
environments would be due to both the absence (1 bird)
or presence (12 birds) of social competition as well as
differences due to bird density (1,085 vs 362 cm 2 per
bird), respectively.
Each room contained eight rows of cages in a fourdeck, modified stair-step arrangement (North and Bell,
1990). Experimental units, consisting of either four
consecutive single-bird cages or one multiple-hen cage,
were repeated twice for each of the three genetic stocks
within a cage row using a restricted randomization
scheme. Water was provided through drip nipples with
a single-caged hen having access to two drip nipples
and the 12 hens of a multiple-bird cage having access to
five drip nipples (Craig and Muir, 1996).
1309
Experiment 1
When the hens were 33 wk of age, an experiment
dealing with a cold environmental temperature was
initiated on January 31. No attempts were made to
regulate humidity. The temperature of two of the four
rooms was decreased to a mean temperature of 0 C for 72 h
with a range of -5 to 7 C. It took 1.5 h to lower the
temperature from control levels. Relative humidity for the
two colder rooms varied from 50 to 74%. The other two
rooms remained at their control temperature (x = 21 C;
range of 18 to 24 C) with relative humidity varying from
35 to 44%. Recording thermographs and humidigraphs
monitored the environment of each of the four rooms
continuously throughout the experiment. Water provided
to the hens via drip nipples remained unfrozen by
allowing it to flow continuously through the polyvinyl
chloride pipes.
Handling stress involved the collection of blood
samples from paired cold and control rooms on two
occasions with different hens being bled on each occasion
following the initiation of the colder temperatures. Hens
were bled 4 to 6 h after a temperature of 0 C was achieved
on Day 1 of the experimental period. Additional hens
were bled 4 to 6 h following the end of the 72 h treatment
of 0 C on Day 3. Data on blood parameters are reported in
the companion paper of Hester et al. (1996). The comb of
each hen exposed to cold was evaluated subjectively for
the presence of frostbite on Day 4.
Experiment 2
The same hens that were exposed to a 0 C temperature
at 33 wk of age were subjected to a mean environmental
temperature of 38 C (range of 32.5 to 41.5 C) for 3 h at 44
wk of age. Relative humidity averaged 36% during the 3 h
heating episode. The same two control rooms used in
Experiment 1 were also used as controls in Experiment 2.
Ambient temperature of the two control rooms was
maintained at 30 C with a relative humidity of 39%.
Hens of the two heated rooms were bled 1 to 3 h after a
mean temperature of 38 C was achieved on Day 1 of the
experimental period. One-half of the control birds was
bled before the birds of the heated environment were
sampled, with the remaining half of the controls bled
immediately following the heating episode (Hester et al.,
1996).
Mortality was monitored continuously throughout the
3-h heating episode. Mortality was recorded for hens
housed in the bottom three cage rows. Hens that
succumbed to the 38 C temperature were removed from
their cages. Twelve hours following the termination of the
38 C temperature, dead birds of the bottom three cage
rows were replaced with hens from the top cage rows of
their respective rooms so as to maintain constant bird
density within the cages throughout the study.
Hens previously subjected to 38 C for 3 h were exposed
to a second heating episode 24 h later on Day 2 of the
experimental period. Using the same schedule as
described for the first heating episode, hens of two rooms
HESTER ET AL.
1310
were subjected to a mean temperature of 38 C (range of
35.5 to 40 C) for 3 h. Relative humidity of the two rooms
averaged 32%. The two control rooms were the same as
used in the first heating episode. Mean temperature of the
two control rooms was 28 C with a relative humidity of
38%. Blood samples were obtained from hens not
previously bled as described for the first heating episode.
Cold Environment
T
8 79
lu
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9
Egg Production
Egg records were maintained daily. Only eggs laid 8 d
prior to, during, and 8 d following the heat and cold
exposures were considered. For information on annual
performance of the hens, see Muir and Liggett (1995).
Statistical Analysis
The incidence of frostbitten combs during cold exposure (Experiment 1) and mortality due to heat exposure
(Experiment 2) were analyzed by chi-square (Steel and
Torrie, 1980). The number of eggs produced 8 d prior to,
during, and 8 d following cold (Experiment 1) and heat
(Experiment 2) exposure was statistically evaluated using
a categorical data analysis suitable for discrete data.
Specifically, the CATMOD procedure of SAS® (SAS
Institute, 1990) as outlined by Grizzle et al. (1969) was
used. Planned comparisons on egg production were made
with the selected vs the control lines as well as the selected
vs the commercial lines. Each comparison of lines was
made during pre-exposure and at the time of exposure as
well as before and after exposure to environmental
extremes.
/
4
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J
Control
Genetic Stock
Control Environment
• Before Cold Stress
• During Cold Stress
H Following Cold Stress
Genetic Stock
FIGURE 1. Hen-day egg production of three genetic lines of laying
hens (selected, control, and commercial) 8 d prior to, during (3 d), and 8 d
following cold and handling exposures.
RESULTS
Experiment 1. Cold Environmental
Temperatures
A cold environment of O C for 72 h did not result in any
hen deaths, although 15.5% of the hens experienced
mildly frostbitten combs. Single-caged hens (x of 42.4 +
2.9%) experienced a higher incidence of frostbite than
hens of multiple cages (x of 6.5 ± 0.8%, P < 0.0001). The
percentage incidences of frostbitten combs for the selected
(4.5 ± 1.2%) and control (3.8 ± 1.1%) lines housed in
multiple-bird cages were significantly lower than that of
the commercial line (11.1 ± 1.9%) housed in multiple-hen
cages (P < 0.0001). The percentage incidence of frostbite
among genetic lines in single-hen cages was similar (43.8 ±
5.1%, 42.7 ± 5.1%, and 40.6 ± 5.0% for selected, control, and
commercial lines, respectively).
For egg production, a significant environmental temperature by time interaction (P < 0.00001) occurred when
the selected vs control lines were compared before and
during exposure to cold (Figure 1). Three days of cold
exposure caused a decline in egg production for both
genetic lines; however, the decrease was greater in the
control line (10.5%) than in the selected line (7.6%).
Although handling and bleeding the birds of the control
environment also caused a decline in egg production, the
decrease was much less than that which occurred when
hens were exposed to both handling and cold temperature. Handling and bleeding the selected birds in the
control environment caused only a 1.2% decrease in egg
production, whereas the control line experienced a 3.9%
decrease in egg production.
A comparison of the selected and commercial lines
prior to and during cold exposure also resulted in a
significant environmental temperature by time interaction
for egg production (P < 0.0001, Figure 1). Both the selected
(7.6%) and the commercial (8.8%) lines showed the same
relative decrease in egg production as a result of cold
temperature. However, within the control environment,
the commercial line showed a greater decrease in eggs laid
(3.6%) than did the selected line (1.3%) as a result of
handling and blood sampling. The environmental temperature by time interaction was nonsignificant when the
genetic lines were compared before and following cold
exposure (Figure 1).
A comparison of the selected with the control line 8 d
prior to and during cold and handling exposures showed
PRODUCTION OF HENS ADAPTED TO MULTIPLE-HEN CAGES
Single-Hen Cages
1311
Although the commercial line always laid more eggs than
the selected line of hens in both single- and multiple-hen
cages and prior to and following exposure to cold,
differences between the lines were more profound in
single-hen cages before cold exposure. A comparison of
the selected line with the control line prior to and
following exposure to cold and handling did not show a
significant interaction for cage size and genetic stock (P <
0.07).
Experiment 2. High Environmental
Temperatures
Time of Cold Stress
Multiple-Hen Cages
During
Time of Cold Stress
FIGURE 2. Hen-day egg production of three genetic lines of laying
hens (selected, control, and commercial) housed in single- or multiplehen cages 8 d prior to, during (3 d), and 8 d following cold and handling
exposures.
a cage size by genetic stock interaction for egg production
(P < 0.05, Figure 2). The selected line always laid more
eggs than the control line both in single- and multiple-hen
cages and prior to and during exposure to cold or
handling. However, within multiple-hen cages, the difference in egg production between the selected and control
lines was much greater during 3 d of cold and handling
stress.
A comparison of the selected line with the commercial
line 8 d prior to and during cold exposure showed a
significant cage size by genetic stock interaction (P < 0.01,
Figure 2). Eight days prior to the period of cold and
handling, which was immediately after peak production,
the commercial hens were laying more eggs than the
selected line in both single- and multiple-hen cages.
During exposure, egg production decreased; the commercial hens continued to outproduce the selected line in
single-hen cages, but not in multiple-hen cages, where egg
production between the two lines was similar.
A comparison of the selected line with the commercial
line prior to and following cold and handling exposures
also showed a significant cage size by genetic stock
interaction for egg production (P < 0.001, Figure 2).
Single-caged hens experienced higher mortality (x of
19.8 + 2.4%) than hens of multiple-bird cages (x of 14.1 ±
1.2%, P < 0.02). During the first heating episode, the
selected line of chickens in multiple-hen cages showed an
increased resistance to heat exposure, as indicated by
lower mortality (9.7 ± 1.8%), when compared to the control
(17.4 ±2.2%) and commercial (15.3 ±2.1%) lines housed in
multiple-hen cages (P < 0.03). Single-caged hens showed
similar mortality among the three genetic lines (17.7 ±
3.9%, 24.0 ±4.4%, and 17.7 ±3.9% for selected, control, and
commercial lines, respectively). The second heating
episode did not result in any hen mortality.
Hen-day egg production 8 d prior to, during (2 d), and 8
d following heat exposure of three genetic lines of layers
housed in either single- or multiple-hen cages is shown in
Figure 3. A comparison of the selected and commercial
lines prior to and during heat exposure showed a
significant genetic stock by cage size by environmental
temperature interaction (P < 0.00001). Two heating
episodes of 3 h each suppressed egg production in both
the selected and commercial lines of chickens; however,
the decrease was greater in single-hen cages (10.0 and
12.4%, respectively) than in multiple-hen cages (7.6 and
5.1%, respectively). Although colony-caged hens of the
selected and commercial lines always laid fewer eggs than
the single-caged hens, the commercial line in colony cages
of the control environment showed a marked reduction in
egg production. Whereas the commercial line outperformed the selected line in single-hen cages in both the
heated and control environments prior to and during heat
exposure, the opposite occurred with hens of multiplebird cages, in that the selected line performed equally well
or better than the commercial line.
A comparison of the selected vs the commercial lines
prior to and following high temperature also showed a
significant genetic stock by cage size by environmental
temperature interaction for egg production (P < 0.00001,
Figure 3). The selected line laid more eggs than the
commercial line in multiple-hen cages, with the opposite
trend occurring in single-hen cages. A comparison of the
8-d period following heat and handling with the
8-d period prior to heat and handling showed that both
genetic lines in single- and multiple-hen cages subjected to
a high environmental temperature had a similar reduction
in rate of lay, which averaged 22%. Part of the three-way
interaction was because the hens of the control environ-
1312
HESTER ET AL.
Heated Environment
Single-Hen Cages
Before
During
Heated Environment
Multiple-Hen Cages
Following
During
Time of Stress
Before
Time of Stress
Control Environment
Single-Hen Cages
Following
Control Environment
Multiple-Hen Cages
95
90
--
c 85
I 80
• Selected
• Control
U Commercial
!
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• •
•
§70« 65
•
.
•
9
S 60x
•
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Before
During
Following
Time of Stress
555045-
ru.
•
•
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Before
••
^ B
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1
• Selected
• Control
E Commercial
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During
Time of Stress
Following
FIGURE 3. Hen-day egg production of three genetic lines of laying hens (selected, control, and commercial) housed in single- or multiple-hen cages
d prior to, during (3 d), and 8 d following heat and handling exposures.
ment, which were subjected to handling but not to a high
environmental temperature during that stress period, also
experienced a decrease in egg production, although less
dramatic, with the colony-caged hens showing a greater
decrease (11.5%) than the single-caged hens (5.0%).
A comparison of the selected vs the control lines prior
to and following heat exposure showed a significant
genetic stock by cage size by environmental temperature
by time interaction for egg production (P < 0.02, Figure 3).
Eight days prior to heat exposure, the control line housed
in multiple-hen cages laid an average of 4.1% fewer eggs
than the selected line of multiple-hen cages. Following
heat exposure, the control line housed in multiple-hen
cages showed a much greater decrease in egg production
(11.2%) than the selected line housed in multiple-hen
cages. In single-hen cages during the 8 d prior to heat
exposure, the selected line laid an average of 4.2% more
eggs than the control line. Following heat exposure, in
which egg production was reduced by 23.6 to 25.8% in
both lines, the same trend of a greater rate of lay with the
selected line than by the control line still prevailed.
However, the differences between the lines following heat
exposure was greater, with the selected lines laying 6.4%
more eggs than the control line.
DISCUSSION
Our hypothesis was that hens selected for adaptation
to a multiple-bird environment should react less intensely to stressors than do the unselected controls.
Turkeys selected for high and low adrenal responses
during cold stress support this hypothesis in that the
low corticosterone lines were less excitable and had
improved production traits (Brown and Nestor, 1973,
1974). Likewise, chickens selected for a high response to
adrenocorticotropin had a shorter survival time of 12
min than the low response line when subjected to acute
heat stress of 45 C (Edens and Siegel, 1975; Siegel, 1981).
The selected line of Leghorns of the current study
showed evidence of improved adaptation to multiplehen cages when compared to the other genetic stocks.
The best evidence of the selected line's resistance to
stress and improved adaptability to multiple-hen cages
was the survival rate under high temperature condi-
PRODUCTION OF HENS ADAPTED TO MULTIPLE-HEN CAGES
tions. During the first heating episode, the selected line
in multiple-hen cages was more resistant to heat than
were the unselected control and commercial lines in
multiple-bird cages, as indicated by a lower mortality
rate. Behavioral changes of the selected line as compared
to the control and commercial lines, including reduced
mortality from cannibalistic pecking and improved
feathering, also supports the hypothesis of improved
adaptation to multiple-hen cages (Craig and Muir, 1996).
A total of 57 hens died in single cages compared to
122 hens of multiple-bird cages. When expressed on a
percentage basis, significantly (P < 0.02) higher mortality
occurred with birds of single cages (19.8%) than with
those of multiple-hen cages (14.1%). These results are
perplexing because the single-caged hens should have
been able to dissipate heat more easily due to more
space allocation (1,085 cm 2 per single-caged bird vs 362
cm 2 per bird of multiple-hen cages). In addition, each
single-caged hen had access to more drip nipple
waterers on a per bird basis than the colony-caged hens.
The acuteness of the first heating episode may have
eliminated the advantages of less crowding and more
waterers for the single-caged hens.
Birds of multiple-bird cages experienced a lower
incidence of frostbitten combs than hens of single cages,
most likely because of their ability to transfer body heat
to one another and maintain a higher core body
temperature during cold exposure. The reason for the
higher incidence of frostbite in the commercial stock
than in the control and selected lines in multiple-bird
cages is unknown, especially as a similar effect was not
apparent in the single cages. Comb size was not
measured; there were no apparent visual differences
among the three lines in comb size at the time that cold
exposure was initiated.
Using egg production as a criterion, the selected line
of chickens withstood social, handling, and environmental stressors better than the control line and, in some
cases, the commercial line of chickens. At 33 wk of age
(Experiment 1), the commercial line laid at a higher rate
of lay than the selected line; however, at 44 wk of age,
the selected line in multiple-hen cages was more
persistent in that it laid more eggs than the commercial
line in multiple-hen cages (Figure 3, Muir and Liggett,
1995). Even at 33 wk of age, when the commercial line
was laying more eggs than the other two lines, the
selected line seemed more able to cope with handling
than the commercial and control lines, as evidenced by
the sharper decline in rate of lay in these latter two
groups during the handling period as compared to prior
to handling (Figure 1, control environment). A combination of handling and cold was more detrimental to egg
production than handling alone, suggesting that the
stressors were additive (McFarlane and Curtis, 1989).
The selected line reacted less intensely to handling and
cold exposure, as indicated by the less severe reduction
in egg production when compared to the control line of
chickens (Figure 1, cold environment).
1313
Although social stressors, induced by a colony cage of
12 hens, were detrimental to egg production immediately after peak production relative to production of
hens in single-bird cages, the rate of lay of the selected
line in multiple-hen cages was not as adversely affected
as it was for the other two lines (Figure 2). A
comparison of the three genetic lines at 33 wk of age
(Experiment 1) showed that the commercial line's rate of
lay was superior to those of the selected and control
lines in single-hen cages before, during, and following
cold exposure; however, in multiple-hen cages during
cold exposure, the selected line performed equally as
well as the commercial line, whereas the rate of lay of
the control line was severely depressed. The selected
line's smaller rate of decrease in egg production during
social interaction, handling, and cold stress showed that
it reacted less intensely.
Egg production at 44 wk of age provided additional
evidence that the selected line of chickens reacted less
adversely to multiple stressors (Experiment 2). The
selected line withstood social competition better than the
control line, as indicated by a higher rate of lay in
multiple-hen cages at 44 wk of age (Figure 3; Muir and
Liggett, 1995). The same statement can be said when
making statistical comparisons of the selected line with
the commercial line. However, because the commercial
line of multiple-bird cages in the control environment
experienced an unexplained reduction in egg production
both before (61.5%) and during (59.7%) the time of
handling stress as compared to their counterparts of the
heated environment (74.5 vs 69.4%, respectively, Figure
3), caution should be used in making this comparison.
Within single-hen cages, the commercial line continued
to lay more eggs than the other two genetic lines. For
the chickens of colony cages following heat and
handling, the selected line did not experience as great a
decrease in egg production as the control line; the rate of
decrease for the commercial line was similar to that of
the selected line.
In conclusion, production traits support the hypothesis that hens selected for adaptation to a multiple-bird
environment are more stress resistant. The selected line
in multiple-hen cages, as compared to the unselected
control and commercial lines of chickens, reacted less
intensely to stressors, as indicated by lower mortality
during heat exposure, and a smaller rate of decline in
egg production in multiple-hen cages as a result of
handling and exposure to temperature extremes.
Of the criteria used to evaluate stress in the current
study and the one dealing with physiological appraisal
(Hester et al., 1996), egg production and mortality
provided the best evidence that the selected line of
chickens was more stress resistant than the control and
commercial lines. The physiological appraisal offered
some evidence of stress resistance in that the selected
line did not show an increase in the heterophil to
lymphocyte ratio as a result of social stress, as did the
other lines of chickens at 33 wk of age. However, trends
were not always consistent; the selected line did not
HESTER ET Ah.
1314
s h o w similar leucocytic responses to cage size at 18 or 44
w k of age. It is b e c a u s e of the lack of consistency in the
h e t e r o p h i l t o l y m p h o c y t e ratios a n d the fact t h a t a d r e n a l
function w a s similar a m o n g the three genetic stocks
u n d e r a v a r i e t y of stressful conditions (Hester et al.,
1996) t h a t p r o d u c t i o n s e r v e d as a better indicator of
stress resistance t h a n the physiological appraisal.
ACKNOWLEDGMENTS
Technical assistance from M a r i s u e Freed, Julie L a d d ,
Jean Craig, Brent L a d d , D e e n a Liggett, Debbie Miles,
Mollie M c C o m b , Jamie Carrigan, a n d K i m Berry w a s
greatly a p p r e c i a t e d . G r a t i t u d e is also expressed to Ken
W o l b e r for the m a n a g e r i a l care of the b i r d s . H a t c h i n g
e g g s of the commercial strain w e r e k i n d l y d o n a t e d b y
DeKalb® P o u l t r y Research, Inc., DeKalb, IL 60115.
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