Effect of Increased Bird Population in a Fixed Cage Area on Production
and Economic Responses of Single Comb White Leghorn Laying Hens!
W. B. ROUSH, M. M. MASHALY, and H. B. GRAVES
Department of Poultry Science, The Pennsylvania State University, University Park, Pennsylvania 16802
(Received for publication December 16, 1982)
1984 Poultry Science 63 :45-48
INTRODUCTION
Poultry managers are increasing the number
of laying hens per cage as a method to reduce
housing, equipment, and labor costs per cage,
although increased bird numbers in a specified
cage area causes a decline in egg production and
increased hen mortality (Lowe and Heywang,
1964; Cook and Dembnicki, 1966; Wilson et
al., 1967; Wayman et a!., 1969; Marks et al.,
1970; Dorminey and Arscott, 1971; Bell and
Swanson, 1975; Hughes, 1975; North, 1978).
Usually the producers feel that the negative
factors associated with the increased number of
birds per cage are offset by the income from
the increased number of eggs produced on a
cage or house basis. However, Martin and Carter
(1980) pointed out that increased bird numbers
can have a negative effect on net profit during
periods of low egg price.
The purpose of this research was to examine
by regression analysis the quantitative relationship between the cage area provided per
hen in cages of fixed dimensions and parameters associated with egg production. The
number of birds was confounded with the cage
area provided per hen, reflecting the situation
faced by a poultry producer who elects to add
or remove hens in a fixed cage system. The
1 Paper No. 6566 in the Journal Series of the
Pennsylvania Agricultural Experiment Station.
economic effect of crowding hens on egg
production and feed consumption on a cage
basis was considered under five egg and five
feed price situations.
METHODS AND PROCEDURES
Dekalb XL pullets were brooded and reared
in positive pressure ventilated floor pens. At 19
weeks of age the pullets were randomly assigned to one of two negative pressure ventilated replicate rooms. The birds were housed
3, 4, or 5 birds per cage (30.5 X 50.8 cm),
which resulted in 516, 387, or 310 cm 2 per
bird, respectively. The experimental unit
in each room was 32 cages per treatment. Thus
for the 3, 4, and 5 bird per cage treatments
there were 192, 256, and 320 birds in each
treatment, respectively, for a total of 768 birds
in the experiment. The hens were fed commercial laying rations formulated according to
feed intake to provide 17 percent protein
starting at 19 weeks and throughout the experiment. Hart trigger cup waterers were used
during both the pullet and laying phases. Feed
and water were provided ad libitum. The
lighting schedule after the first three 24-hr days
was reduced to 10 hr of light daily until the
19th week following which the lights were
increased by 30 min per week for 4 weeks, and
then 15 min per week until a total of 17 hr of
light w'ts provided daily.
45
Downloaded from http://ps.oxfordjournals.org/ at Penn State University (Paterno Lib) on February 20, 2016
ABSTRACT Quantitative relationships between the cage area allotted per hen and parameters
associated with egg production were examined by regression analysis. Hens were placed 3,4, and 5
birds per cage (30.5 X 50.8 em) with 516, 387, and 310 cm 2 of floor area per hen, respectively.
Egg production declined as the area per hen was reduced. There was no numerical difference for
feed consumption per dozen eggs between 516 or 387 cm 2 per hen. Feed conversion was less
efficient when the area was reduced to 310 em 2 per hen. Feed conversion when adjusted to 20
dozen eggs accentuated the decline in efficiency as previously noted. Mortality was significantly
related to a reduction in cage area per hen. Egg weight tended to increase as the allotted area per
bird decreased. Eggs produced and feed consumed per cage were highly correlated to bird numbers
per cage area. An economic analysis based on dozens of eggs produced, feed consumption, egg and
feed prices, grower payment, and pullet cost showed that profitability associated with increased
bird numbers in a fixed cage area is sensitive to changes in egg and feed prices.
(Key words: bird density, production economics, laying hen)
46
ROUSH ET AL.
RESULTS AND DISCUSSION
Regression equations describing the linear
relationships between various production parameters and area per hen are shown in Table 1.
Egg production, both on a hen-housed and a
hen-day basis, declined as the area per hen was
reduced, in agreement with previous studies
(Lowe and Heywang, 1964; Cook and Dembnicki, 1966; Wilson et at., 1967; Wayman
et at., 1969; Marks et at., 1970; Dorminey and
Arscott, 1971; Bell and Swanson, 1975; Hughes,
1975; North, 1978). Equations describing these
relationships for the hen-housed and hen-day
production had probabilities of .0727 (r2 = .59)
and .1854 (r2 = .39), respectively.
Although there was no numerical difference
in feed consumption per dozen eggs between
populations of 3 or 4 hens with 516 or 387
cm 2 per hen, respectively, feed conversion was
less efficient when 5 birds were placed in the
cages with 310 cm 2 per hen. Wayman et at.
(1969) and Bell and Swanson (1975) showed a
general trend for feed efficiency to be less with
increased numbers of birds per cage.
To equalize the comparison of feed conversion ratios, consumption was equated to 20
dozen eggs per hen. This procedure tended to
accentuate the decline in efficiency noted. The
equation describing this relationship had a
probability level of .1305 (r2 = .47).
Average bird weight showed a slight tendency (P = .1086, r2 = .51) to decrease as the
cage area for the birds was reduced. The tendency of body weight to decrease with increased
birds per cage is in agreement with the previous
work of Wilson et at. (1967), Dorminey and
Arscott (1971), and Dorminey et at. (1972).
Cook and Dembnicki (1966) and Wayman et at.
(1969) did not notice a decrease in body weight
or gain, respectively, with increased bird
numbers.
Mortality was significantly (P = .049, r2 =
.66) related to a reduction in area allocated per
hen in agreement with the previous work (Lowe
and Heywang, 1964; Logan, 1965; Cook and
Dembnicki, 1966; Wilson et at., 1967; Dorminey
and Arscott, 1971).
Egg weight tended to increase as the area per
bird was reduced (P = .1985, r2 = .37), as
previously observed by Cook and Dembnicki
(1966) and Dorminey and Arscott (1971). This
tendency may be related to the fact that
TABLE 1. Relationship between laying hen production parameters and the cage area provided per hen
Parameter
(Y)
Egg production,
hen-housed, %
Egg production,
hen-day, %
Feed/dozen, kg
Feed/dozen adjusted, kg
Body weight, kg
Mortality, %
Egg weight, g
Dozen/cage
Feed/cage, kg
516
387
em' /hen,' em' /hen,
3 hens
4 hens
310
em' /hen,
5 hens
Equation'
Probability
r'
77.9
76.3
71.0
y= 62.49
+.031x
.0727
.59
80.0
78.5
75.9
y=
70.32
+.019x
.1854
.39
y=
y=
y=
y=
y=
Y=
Y=
1.85
2.38
1.571
13.3
63.4
128.3
226.7
-.00045x
- .0013x
+.0002x
- .018x
-.005x
- .140x
- .268x
.2494
.1305
.1086
.0490
.1985
.0001
.0003
.31
.47
.51
.66
.37
.98
.97
1.63
1.75
1.684
4.2
60.8
56.1
90.4
1.63
1.78
1.645
6.3
61.2
73.3
117.8
1.74
2.04
1.642
7.9
61.9
85.2
146.9
'Number of hens per eage area of 1549 em'.
'y = parameter that is being related to area per hen; x = square centimeters of area per hen.
Downloaded from http://ps.oxfordjournals.org/ at Penn State University (Paterno Lib) on February 20, 2016
Data collection for egg production and feed
consumption commenced when the hens
reached 25% egg production and continued for
288 days. Total eggs produced, feed consumed,
and mortality for each treatment replicate were
used in calculation of the egg production
parameters. Egg and body weight values were
averages taken at the end of each of 11 28-day
periods. The periods started when the birds
were housed at 19 weeks.
Statistical analysis was conducted using the
General Linear Models (GLM) procedure of
the Statistical Analysis System statistical
package (Helwig and Council, 1979). Levels
of attained significance were reported for
each model (Gill, 1981).
47
CAGED HEN DENSITY
TABLE 2. Profit potential ($) per cage for three cage populations under various egg and feed prices'
Blended
egg
price
Hens/cage area'
Feed price
180
190
($/doz)
200
210
220
($/ton)
.35
.45
.55
.65
.75
-6.604
-.994
4.616
10.226
15.836
-7.599
-1.989
3.621
9.231
14.841
-8.593
-2.983
2.627
8.237
13.847
-9.587
-3.977
1.633
7.243
12.853
-10.582
-4.972
.638
6.248
11.858
4 hens, 387 cm' /hen
.35
.45
.55
.65
.75
-8.789
-1.459
5.871
13.201
20.531
-10.085
-2.755
4.575
11.905
19.235
-11.381
-4.051
3.279
10.609
17.939
-12.677
-5.347
1.983
9.313
16.643
-13.973
-6.643
.687
8.017
15.347
5 hens, 31 0 cm' /hen
.35
.45
.55
.65
.75
-13.166
-4.646
3.874
12.394
20.914
-14.782
-6.262
2.258
10.778
19.298
-16.398
-7.878
.642
9.162
17.682
-18.014
-9.494
-.974
7.546
16.066
-19.630
-11.110
-2.590
5.930
14.450
1 Profit potential ($) per cage = (EP X Dz/Cage) (FP X FC/Cage) - (Hen X PGP) - (Hen X PC) Where
EP = blended egg price; Dz/Cage = dozen eggs produced per cage; FP = feed price; FC/Cage = feed consumption
per cage; Hen = hen number; PGP = pullet grower payment, $.44; PC = pullet cost, $2.34.
'Cage area
= 1549 cm'.
because birds would be laying fewer eggs with a
reduced cage area, their eggs would be larger.
A high correlation was noted for the cage
area provided and dozens of eggs produced (P =
.0001, r2 = .98) and feed consumed per cage (P
= .0003, r2 = .97). These two production
factors are important in the argument for or
against increasing the number of hens per cage
area, as they are major factors affecting the
economics of an egg operation. Examination of
TABLE 3. Most profitable cage populations under
various egg and feed price situations'
Blended
egg
price
($/doz)
$180
$190
$200
$210
$220
.35
.45
.55
.65
.75
A
A
B
B
C
A
A
B
B
C
A
A
B
B
B
A
A
B
B
B
A
A
B
B
B
Feed price per ton
'A
3 birds/cage with 516 cm' per hen; B =
4 birds/cage with 387 cm' per hen; C = 5 birds/
cage with 310 cm' per hen.
data on a per bird basis for studies on crowding
yields valuable information on biological effects
but does not necessarily give information on
which economic decisions can be made. Data
examined on a unit (cage) basis would be more
appropriate for economic analysis.
Table 2 shows the effect of area per hen
(and number of birds per cage area), feed price,
and blended egg price on profit potential
adjusted for pullet cost and grower payments.
The choice of the most profitable area per bird
was sensitive to changes in egg and feed prices.
For example, when the egg price was $.65/
dozen and the feed price was $190 per ton, the
profit potential was $9.231, $11.905, and
$10.778 per cage for cage allotments of 516,
387, and 310 cm 2 , respectively. The most
profitable area per bird would be 387 cm 2 (4
birds per cage). However if the price of eggs was
raised to $.75 per dozen and the feed price
remained at $190 per 'ton, a slightly higher
profit ($.063) would be realized by the 310
cm 2 cages (5 birds each). Table 3 summarizes
the most profitable cage popUlations for various
egg and feed price situations under the conditions of this experiment. The short production
cycle used in this experiment may not fully
Downloaded from http://ps.oxfordjournals.org/ at Penn State University (Paterno Lib) on February 20, 2016
3 hens, 516 cm' /hen
48
ROUSH ET AL.
REFERENCES
Bell, D. D., and M. H. Swanson, 1975. Crowding of
chickens in cages reduces your profits. Univ.
California Leaflet 2273.
Cook, R. E., and E. F. Dembnicki, 1966. Performance
and interactions of seven egg production stocks
in three cage housing regimens. Poultry Sci.
45:17-21.
Dorminey, R. W., and G. H. Arscott, 1971. Effects of
bird density, nutrient density and perches on the
performance of caged White Leghorn layers.
Poultry Sci. 50: 619-626.
Dorminey, R. W., G. H. Arscott, and P. E. Bernier,
1972. Performance of dwarf White Leghorn
layers as affected by cage size, bird density and
perches. Poultry Sci. 51: 1658-1662.
Gill, J. L., 1981. Evolution of statistical design and
analysis of experiments. J. Dairy Sci. 64: 14941519.
Helwig, J. T., and K. A. Council, ed., 1979. SAS User's
Guide. SAS Inst., Cary, NC.
Hughes, B. 0., 1975. The concept on an optimum
stocking density and its selection for egg produc·
tion. Pages 271-298 in Economic Factors
Affecting Egg Production. Symposium Number
10. B. M. Freeman and K. N. Boorman, ed. Br.
Poult. Sci. Ltd., Edinburgh.
Logan, V. A., 1965. Influence of cage versus floor,
density and dubbing on laying house performance. Poultry Sci. 44: 974-979.
Lowe, R. W., and B. W. Heywang, 1964. Performance
of single and multiple caged White Leghorn
layers. Poultry Sci. 43:801-805.
Marks, H. L., L. D. Tindell, and R. H. Lowe, 1970.
Performance of egg production stocks under
three cage densities. Poultry Sci. 49: 1094-1100.
Martin, G. A., and T. A. Carter, 1980. You'll be better
off with one less layer per cage. Poultry Dig.: 340,
342.
North, M. 0., 1978. Commercial Chicken Production
Manual. 2nd ed. Avi Publ. Co., Inc., Westport,
CT.
Wayman, 0., T. Pirzada, R. B. Herrick, and K. Morita,
1969. A further study on the effect of concentration on the performance of caged layers in
Hawaii. Hawaii Agric. Exp. Sta. Res. Rep. 173.
Wilson, H. R., J. E. Jones, and R. W. Dorminey, 1967.
Performance of layers under various cage regimens. Poultry Sci. 46:422-425.
Downloaded from http://ps.oxfordjournals.org/ at Penn State University (Paterno Lib) on February 20, 2016
reflect the adverse economic effect of a higher
bird population in a longer production cycle. In
general, under periods of undesirable economic
conditions, a fewer number of birds per cage
reduces risk, provides more flexibility, and
would be more profitable. However, it is noted
that the lowest bird density (3 birds per cage
with 516 em 2 /bird) was indicated to be profitable only in situations of minimizing economic
losses rather than maximizing profit.
The results shown in Tables 2 and 3 illustrate
that the profitability of a certain number of
birds per cage area can vary according to egg or
feed price. Other management factors were not
considered, as this experiment was designed to
investigate the production and economic effects
of increasing the population of hens in cages
designed for lower bird numbers. As Bell and
Swanson (1975) point out, it is difficult for
most poultrymen to visualize that fewer hens
can make more revenue than a more crowded
flock. The problem is that along with the
crowding of birds comes a reduction in production performance. Under economic conditions
of low egg prices and a high feed cost, this
reduction in performance is not compensated
by economic savings in labor, housing, or
equipment costs.