232
HAGGER,
The contribution of important traits
caloric (fat) restriction and calorie: protein ratio. Poult.
Sei. 63, 1190- 1200.
ÜNONIWU, J. C., R. G. THOMSON, H. c. CARLSON, R. J.
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PASS, D. A., 1983 : A cardiomyopathy (Sudden Death
Syndrome) of adult hens. Avian Path. 12, 363 - 369.
SEEMANN, G ., 1981: Die Reaktionen von Broilern verschiedener Herkünfte auf eine verlängerte Mast (Gesundheit, Mast- und Schlachtleistung). Dissertation Hohenheim.
Arch. Geflügelk. 1993, 57 (5), 232-236, ISSN 0003-9098.
STEELE, P., J. EDGAR, 1982: Importance of acute death
syndrome in mortalities in broiler chicken flocks. Austr.
Vet. J. 52, 63 - 66.
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Kurzmast-Hähnchen durch Verfütterung eines nährstoffarmen Starterfutters. Lohmann Information 9/10.
Anschr ift der Verfasser: Priv .-Doz. Dr. M. Grashorn, 470 Kleintierzucht, Uni\·ersität
Hohenhci m, 70593 Stuctgarc; Prof. Dr. H. G. Classcn, 140 Ph armakolog ie und Toxikolog ie der Ernährung, Un iversität Hohenheim, 70593 Stuctgarc
© Verlag Eugen Ulmer GmbH
& Co., Stuttgart
The contribution of important traits to income minus feed cost
of laying hens under various feed-price/egg-price ratios
Der Beitrag wichtiger Merkmale zum Eierlös minus den Futterkosten von Legehennen
unter verschiedenen Relationen von Futter- und Eierpreis
C. Hagger
Manuskript eingegangen am 20. November 1992
lntroduction
Revenues from egg sale are the only relevant source of
income from laying hens and are dependent on egg price
system, number of saleable eggs and feed price. Egg weight
is almost everywhere by far the most important trait to
decide the price of an egg. Therefore, income from eggs
sold minus cost of feed eaten determines the economic
success of egg production to a large extent. The expected
number of eggs per hen, their distribution in weight
(= price) dasses and the expected body weight should provide
adeq uate information to evaluate available laying stocks for
their profitability, once the relationships between these traits
and income minus feed cost have been established for various
economic systems, i. e. combinations of egg price and feed
price.
The aim of the investigation was to estimate the contributions of egg number, egg weight and body weight to income
minus feed cost in 12 economic systems and for two distinct
populations from data of one generation of a selection
experiment for genetically improving income minus feed
cost in pullets.
Material and Methods
Individual records on egg number, egg weight, feed intake
and body weight at end of period were available from the
In stitute of Anima! Sciences, Swiss Federal In stitute of Technology,
Zurich
6th generation of a selection experiment that aimed to
improve by genetic progress income minus feed cost in
brown egg layers (HAG GER, 1990; 1992). Data from 1102
survivors to 40 weeks (PERl) and fro~ 1068 survivors to
60 weeks (PER2) with less than 10 kg of feed intake per
1 kg of egg mass produced in both periods, could be used.
Hens had been kept in three-tier, single cage batteries of
1350 cm 2 floor space. Twelve hours of light were provided
until week 40 and gradually increased to 15 h thereafter.
Eggs were counted and weighed daily at the beginning of
the laying period and on 6 days a week from the 26th week
of age on. Records were adjusted to 28 day records for
missing test days using individual information on rate of
lay and egg weight. All eggs which could be weighed were
taken as saleable. Individual feed intake was recorded
continuously for all hens between 21 and 60 weeks. Body
weights were taken at 20, 30, 40 and 60 weeks.
To make the investigations independent from monetary
units and, therefore, make the results applicable for a range
of situations, the necessary prices for feed and eggs to
calculate income minus feed cost (IFC) were taken in number
of Standard eggs. The Figure contains the seven egg weight
dasses used and shows, that an egg of 60- 64 g (weig ht
d ass 3) was taken as the price Standard. Three egg price
systems (Fig.), a steep, a medium and a flat, linear dependence of egg price on egg weig ht dass (SYS l, SYS2,
SYS3) of .2, .1 and .05 price units ( = standard eggs)
between two adjacent weight dasses were modeled. The
ratios between the prices of the two most extreme dasses
were 7.0, 2.0 and 1.38 for the three systems, respectively.
Feed prices of2.0, 2.5, 3.0 and 3.5 Standard eggs per kilogram
Archiv für Geflügelkunde 5/ 1993
HAGG ER,
The contribution of important traits
233
Table 1. Distribution of total egg production on weight classes in the two periods, (%)
Vertei/1111g der gelegten Eier 011/ die Geivichtsklosse11 i11 den zwei Perioden, (%)
Egg weight classes
Period
>69 g
65 - 69 g
60- 64 g
55- 59 g
50- 54 g
45- 49 g
<45 g
PER 1 (21 - 40 wk)
PER 2 (41 - 60 wk)
10.4
36.1
17.7
32.1
26.7
24.0
24.5
7.0
14.1
0.7
5.2
0.1
1.4
0.1
were chosen. Altogether, 12 econornic systems, i. e. combinations of egg price and feed price, were investigated.
Period will be used here as interchangable (eguivalent) with
population, because the different distribution of eggs on the
weight classes in the two periods can be regarded as the
characteristic difference between two populations. To get
absolute figures for a particular system, the actual price of
a Standard egg can be taken and multiplied with the results
of the investigation.
The clistribution of the eggs produced by a hen on the
weight classes was determined for both periods. Average
percentages of eggs in the different classes are given in
Table 1. For all hens, income minus feed cost was calculated
for all economic systems investigated.
The individual contribution of egg number (EN), average
egg weight (EW) and body weight at end of period (BW)
on IFC (in standard eggs) were estimated for the economic
systems mentioned and both periods by a stepwise, multiple
linear regression including the intercept (BMDP2R) . In a
stepwise analysis, the seguence of the sguared multiple
correlation coefficient, R 2 s, provides i1,1sight into the impor-
tance of various combinations of the independent traits to
explain the variation of the dependent trait. The relative
portion of the variance of IFC which is explained by the
final model, is given by its R 2 .
Resu!ts and Discussions
Average performances of the hens are given in Table 2 for
both periods. The largest differences of corresponding traits
between periods were found for E and EW. The increase
in EW led to a dramatic shift of eggs into the higher priced
classes (Tab. 1) in PER2. The percentage of eggs in weight
classes 1 and 2 increased from 28.1 % in PER 1 to 68.2%
in PER2. Averages of IFC, in number of Standard eggs, in
the economic systems evaluated are in Table 3 for both
periods. The ranges extend from 56.1 to 85. 9 and from 53.0
to 92.6 in PER1 and PER2, respectively. The !arger
variation in PER2 is a conseguence of the fact that the
more extreme a population is, the less adaptable it is to
changes in the econornic system. If a standard egg has a
price of 0.1 Ecu then, IFC under SYS1 and a feed price of
2.0 has a value of 7.97 Ecu in PER1.
Table 2. Population means and standard deviation s of traits
D11rchsch11itte 1111d Sta11dardabweich1111gen der Merkmale
Fig. 1. Egg price systems
Eipreis.rysteme
Period 2
Period 1
Trait
Mean
S.D.
Mean
S.D.
Egg number
Egg weight, g
Bod y weight, kg
Feed intake, kg
119.3
60.5
2.26
15.72
H .91
4.84
0.259
1.371
105.2
67 .7
2.38
16.37
19.14
5.30
0.309
1.607
Egg price systems
Eipreissysteme
1.40
Table 3. Average income minus feed cost (IFC) per hen for the
different combinations of egg-price system and feed price, in
Standard eggs
Durchsch11ittlicher Eierlös mi11us F11tterkoste11 ( I FC) pro Henne bei
verschiedenen Kombi11ationen von Eipreis.rystem u11d F11tterkosten, i11 S 1011dardeiern
IFC
Feed price, standard eggs
per kg
Egg-price
system
2.0
2.5
3.0
3.5
2
3
79.7
83.8
85.9
71.8
75.9
78.0
63.9
68.1
70.1
56.1
60.2
62.3
1
2
3
92.6
82.6
77 .6
84.4
74.4
69.4
Period 1
Period 2
Archiv für Geflügelkunde 5/1993
~SYSl
0000€) SYS2
"·
CX3EI3El SYS3
··..
1.20
G„
13-
·a
_----o>··..
-
"El _-.,_~·· ••.
1.00
<l!
u
·;:
0.80
Q_
cn
cn
<l!
··.„.„„.
··:ii..•.
0.60
·„.....
··· ...
<l!
~
0
<l!
0 .40
·„.
·„...
·······:o.
Cl:'.
0.20
0.00
69
65-69 60-64
2
3
55-59
4
50-54 45-49
5
Egg we ight closs
76.2
66 .2
61.2
·.:6.
68.1
58.0
53.0
6
45g
7
234
HAGGER,
The contribucion of important traits
Table 4. Partial regression coefficients of egg number (EN), egg weight (EW) and body weight (BW) on income minus feed cost (IFC)
in standard eggs, for the economic systems investigated and both periods
Partielle Regressiomkoeffizienten von Eizahl ( E N), Eigeivicht ( EW) 1111d Körpergeivicht ( BW) auf Eierlb"s 111i1111s de11 F11tterk'oste11 ( 1 FC) i11
Sta11dardeiem,für die u11ters11chten Preissysteme 1111d beide Perioden.
Partial regression coefficients
Period 2
Period 1
Egg-price
Feed price, standard eggs per kg
2.0
2.5
3.0
3.5
2
3
.87
.89
.90
.85
.87
.88
.83
.85
.86
.80
.83
.84
1.10
1.01
.97
1.09
1.00
.95
1.07
.98
.93
1.05
.96
.91
2
3
4.25
2.05
0.95
4.21
2.01
0.91
4.17
1.97
0.87
4.13
1.93
0.83
2.97
1.40
0.62
2.93
1.36
0.58
2.89
1.32
0.54
2.85
1.28
0.50
1
2
3
-0.73
-0.72
-0.71
-0.91
-0.90
-0.88
-1.09
-1.07
-1.06
-1.26
-1.25
-1.24
-0.76
-0.69
-0.65
-0.91
-0.84
-0.80
-1.07
-0.99
-0.95
-1.22
-1.14
-1 .10
EW (1 g)
BW (100 g)
3.5
3.0
2.5
2.0
system
Trait
The partial regression coefficients of E r , EW and BW
on IFC are summarized in Table 4 for all situations in both
periods. These coefficients are the estimated changes of IFC
in Standard eggs if Er , EW and BW change for 1 egg, 1 g
or 100 g, respectively.
lt should be remembered that these changes in IFC are
expected under the assumption, that all other traits in the
model remain unchanged. Because these expected changes
are phenotypic, they could directly be used to evaluate the
economic consequences of changes of management, e. g.
feedin g practice, which might cause changes in the phenotypic performances of the population .
The contribution of 1 additional average sized egg to IFC
extends between .80 and .90, and between .91 and 1.10
standard eggs in PER 1 and PER2, respectively (Table 4).
These contributions decrease somewhat with increasing feed
price in both periods, and are quite sensitive to changes of
the egg-price system in PER2. In PER1 one additional egg
adds about 3.6% more to IFC in SYS3 than in SYS1, whereas
this figure changes to -12.8% in PER2. lt is obvious that
in a population with an already hig h EW (PER2), increasing
the E adds substantially more to IFC than increasing this
trait in a population with considerably lower egg weight
(PER1).
Table 5. Partial correlations and sequence of multiple correlations (R 2 ) from stepwise linear regressions of EN, EW and BW on IFC
Partielle Korrelationen 1111d aufei11a11derfolgende m11ltiple Korrelatio11en ( R 2 ) a11s schrittJJJeisen linearen R egressionen vo11 E iV, EW 1111d B W a11f I FC
Multiple correlations
Partial correlations
Egg-price
Period 1
Peri od 2
Feed price, Standard eggs per kg
Trait
system
2.0
2.5
3.0
3.5
2.0
2.5
3.0
3.5
EN
1
2
3
0.94
0.98
0.99
0.94
0.97
0.98
0.93
0.96
0.97
0.92
0.95
0.96
0.97
0.50
0.81
0.96
0.49
0.80
0.95
0.48
0.78
0.94
0.46
0.75
EW
1
2
3
0.98
0.98
0.94
0.98
0.97
0.91
0.98
0.96
0.87
0.98
0.95
0.82
0.76
0.96
0.95
0.76
0.94
0.93
0.76
0.92
0.90
0.76
0.90
0.86
BW
1
2
3
-0.46
-0.64
-0.73
-0.53
-0.68
-0.74
-0.58
-0.71
-0.75
-0.61
-0.72
-0.76
0.97
0.98
0.98
0.97
0.97
0.97
0.97
0.96
0.96
0.96
0.95
0.94
EN
1
2
3
0.96
0.98
0.99
0.95
0.98
0.99
0.95
0.98
0.98
0.94
0.97
0.98
0.58
0.83
0.94
0.57
0.83
0.94
0.56
0.82
0.92
0.56
0.81
0.91
2
3
0.93
0.90
0.81
0.92
0.88
0.74
0.91
0.86
0.67
0.91
0.83
0.59
0.93
0.96
0.97
0.92
0.95
0.96
0.91
0.93
0.94
0.90
0.92
0.94
1
2
3
-0.34
-0.51
-0.64
-0.39
-0.56
-0.66
-0.44
-0.59
-0.67
-0.48
-0.62
-0.68
0.94
0.97
0.98
0.93
0.96
0.98
0.93
0.96
0.97
0.92
0.95
0.96
EW
BW
Archiv für
~efl ügel k un dc
Sf1 993
HAGGER,
The contribution of 1 additional gram of EW to IFC
extends between .83 and 4.2S, and between .SO and 2.97
Standard eggs in PER1 and PER2, respectively. These
contributions are !arge in economic systems with a steep
dependence of egg price on egg weight. Increasing EW
furth er in a population with an already high level (PER2)
adds less to IFC than the same change in a population with
a low level. However, an increase in this trait seems still to
be worthwhile under certain egg-price systems. In SYS3 of
P E R1 and feed prices o f 3.0 and 3.S one additional egg
would contribute the same amount to IFC as one additional
gra m of EW. Increasing feed prices gradually reduce the
contributions of positive EW changes to IFC. In the selection
experiment aimed for genetic improvement ofIFC in pullets
(HAGGER, 1992), from which these data originated, EW
increased substantially under an egg price system similar to
SYS2.
The contribution of a reduction of 100 g of BW to IFC
extends between .71 and 1.26, and between .6S and 1.22
Standard eggs in PER1 and PER2, respectively. The contributions are nearly constant for the three systems within
feed prices and PER1, but they are substantially !arger for
a feed price of 3.S than of 2.0. In PER2 the contributions
of BW changes are clearly reduced from SYS1 to SYS3.
The largest differences between the two periods occur under
SYS3.
Partial correlations with IFC of the three variables
included in the regression are given in Table S. In all
economic situations and in both periods EN gets a high
value equal to or above 0.92, i. e„ the correlation among
IFC and EN remains hig h even if IFC is adjusted for the
other two independent traits. In PER1 EW also shows very
high partial correlations with IFC in SYS 1 and SYS 2, but,
in SYS3 it already looses importance with increasing feed
price. In PER2 this decrease of importance starts already in
SYS2 and the dependence on feed price is considerably
stronger. The combination of PER2, SYS3 and feed price
of 3.S is the only situation where the absolute value of the
partial correlation with EW falls below that of BW, but
overall, BW has the smallest values. lt increases from SYS1
to SYS3 and with increasing feed price.
The sequences of R 2 of the stepwise regressions are gi ven
in Table S for all situations and both periods. Egg number
was always the trait which entered the regression equation
first, except in SYS1 of PER1, where EW entered first . lf
EN entered first, it explained between 46 % and 81 % of the
variance o f IFC in PER1 and between S6 % and 94% in
P E R2. If EW entered first, it explained about 76% of the
variance of IFC. Egg number and EW together explained
between 86% and 97%, and between 90 % and 97% of the
variance of IFC in PER1 and PER2, respectively . The
contribution of BW in PER1 was increasing from SYS1 to
SYS3 and also with increasing feed price. In PER2 the
contribution from BW was only small.
The R 2 for the full model were very high, between 94%
and 98%, and between 92% and 99 % in PER1 and PER2,
respectively.
The investigation shows that for certain economic systems, sizable differences in average IFC may exist between
populations of layi ng hens. In SYS2, i. e., under a medium
dependence of egg price on egg weight, the two populations
(= periods) analysed would be about equally profitable,
whereas in the other two systems, either one or the other
po pulatio n would have a distinct advantage (Tab. 3). The
Archiv für Geflügelkunde 5/1993
The contribu tion of important traits
235
contributions of a phenotypic change in the traits investigated are dependent on the economic system and the
population. From corresponding ratios of partial regression
coefficients in Table 4 it can be found that in "PE R 1
average changes of S.O, 2.3 and 1.0 eggs do produce the
same changes in IFC as does a change of 1 g of EW under
the three egg price systems, respectively. In period 2 these
figures are 2.7, 1.4 and .6 eggs, respectively. These values
of the necessary changes in EN are rather constant within
egg price systems. In some contrast to EN are the necessary
changes of BW to yield an equal change in IFC as does a
change of 1 g of EW. The influence of BW is stron gly
dependent on egg price system and on feed price. In PE R1
changes in BW would have to be between S80 & 330, 28S
& 1SS, and 13S & 6S g within SYS1 , SYS2 and SYS3,
respectively, to yield an equal change in IFC as does a change
of 1 g of EW . In PER2 the corresponding ranges of
necessary changes are between 390 & 23S, 20S & 110, and
9S &4S g, respectively.
In summary it can be concluded that if there exist laying
stocks which differ in economically important traits as, e.g.,
egg number, egg weight or bod y weight, it is likely that
they also rank differently according to income minu s feed
cost under different egg-price systems and feed prices.
Therefore, a careful selection among those stocks for a given
economic system should help the producer to maximize
profitabili-t y of egg production .
lt should be pointed out that other specific traits of a
certain stock of laying hens, e.g., percentage of cracked
eggs, which may directly influence IFC, could not be taken
into account in this investigation.
Summary
Profitability of two types of la ying hens was analysed for
the combinations of three egg-price systems and four feed
prices . A standard egg of 60- 64 g was taken as the base of
the comparison. The egg-price systems consisted of seven
weight classes with price ratios between the most extreme
classes of7.0, 2.0 and 1.38. Feed prices of2.0, 2.S, 3.0 and 3.S
standard eggs per kilo gram were investigated . The contributions to income minus feed cost (IFC) from changes in egg
number (EN), egg weight (EW) and body weight (BW)
were estimated by a stepwise multiple linear reg ression.
Observations on 1102 hens in the first period (21 to 40
weeks of age) and on 1086 hens in the second peri od (41
to 60 weeks of age) were available. D ata of the two peri od s
can be regarded as if it were from two populations with
distinct differences in the traits of interest.
Income minus feed cost per average hen was between
S6.1 and 8S .9, and between S3 .0 and 92.6 Standard eggs in
the two periods, respectively. The contributions of 1
additional egg to IFC were between .80 and .90, and between
.91and1 .10 Standard eggs in the two periods respectively.
In the second period these contributions were moderatel y
dependent on the egg-price system. The contributions of 1
additional gram of EW to IFC were between .83 and 4.2S,
and between .SO and 2.97 standard eggs in the two periods
respectively. Under certain egg-price systems, increasing this
trait even in populations with an already high level, seems
tobe worthwhile. The contribution of a reduction of 100 g
of BW to IFC were between .71 and 1.26, and between .6S
and 1.22 standard eggs in the two periods respectively. These
contributions clearly increase with increasing feed price.
236
HA GGER,
The co ntribution of impo rtant traits
D er Beitrag 1vichtiger Merkmale zum Eierlös minus den Futterkosten von L egehennen unter einigen Futterpreis/Eipreis Verhältnissen.
C. HAGGER
Zusammenfassung
Die Wirtschaftlichkeit von zwei Legehennentypen wurde
für die Kombinati o nen von drei Eipreissystemen und vier
Futterpreisen untersucht. Als Vergleichsgröße diente ein
Standardei von 60- 64 g Gewicht. Die Eipreissysteme enthielten sieben Gewichtsklassen mit Preisverhälmissen von
7.0, 2.0 und 1.38 je zwischen der höchsten und der tiefsten
Klasse. Die untersuchten Futterpreise betrugen 2.0, 2.5, 3.0
und 3.5 Standardeier pro Kilogra mm. Die Beiträge an die
Zielgröße Eierlös minus den Futterkosten (IFC), resultierend aus Veränderungen in der Eizahl (EN ), im Eigewicht
(EW) und im Körpergewicht (BW) wurden mit einer
schrittweisen mehrfachen linearen Regression geschätzt. Es
standen Beobachtungen an 1102 Hennen in der ersten
Periode (21. - 40 . Woche) und an 1068 Hennen in der zweiten Periode (41 .- 60. Woche) zur Verfügung. Die beiden
Perioden konnten als zwei Populationen mit deutlichen
Unterschieden in wichtigen Leist ungsmerkmalen betrachtet
werden.
Für E ierlös minus den Futterkosten wurden pro Durchschnittshenne Werte zwischen 56.1 und 85.9 Standardeier
in der ersten und zwischen 53.0 und 92.6 in der zweiten
Periode gefunden. D ie Beiträge eines zusätzlichen E ies zum
IFC lagen in den beiden Perioden zwischen .80 und .90,
und zwischen .91 und 1.10 Standardeiern. In der zweiten
Periode wurden sie deutlich vom Eipreissystem beeinflußt.
Die Beiträge eines zusätzlichen Gramms an EW zum IFC
lagen in den beiden Perioden zwischen .83 und 4.25, und
zwischen .50 und 2.97 Standardeiern. Unter gewissen Eipreissystemen scheint eine weitere Erhöhung des Eigewichts
sogar in solchen Populationen wirtschaftlich positive Auswirkungen zu haben, die schon ein hohes Nivea u aufweisen.
Die Beiträge einer Reduktion des BW um 100 g zum IFC
lagen in den beiden Perioden zwischen .71 und 1.26, und
zwischen .65 und 1.22 Standardeiern. Diese Beiträge stiegen
mit zunehmenden Futterpreis an.
Stichworte
Legehenne, Eierzeugung, Wirtschaftlichkeit, Eierpreis, Futterpreis, Eizahl, Eigewicht, Körpergewicht
References
HAGGER, C. (1990) Responses from selection on income
minus food cost in laying hens, estimated via the animal
model. Brit. Poult. Sei. 31 , 701 - 713.
HAGGER, C. (1992) Two generations of selection o n restricted best linear unbiased prediction breeding values
for income minus feed cost in layi ng hens. J. Anim . Sei.
70, 2045 - 2052.
Anschrift des Ve rfassers: Ch. Haggcr, Institut für Nutztierwissenschaften, ET H-Zentrum
WEN, CH-8092 Zürich, Schweiz.
Archiv für Geflügelkunde 5/1993