ral
ssBioMed CentBMC Genomics
Open AcceResearch article
Microsatellite mapping of QTL affecting growth, feed consumption, 
egg production, tonic immobility and body temperature of Japanese 
quail
Francis Minvielle*1, Boniface B Kayang2,3, Miho Inoue-Murayama2, 
Mitsuru Miwa2, Alain Vignal3, David Gourichon4, André Neau5, Jean-
Louis Monvoisin1 and Shin'ichi Ito2
Address: 1Génétique et Diversité Animales, Institut National de la Recherche Agronomique, Centre de Jouy, 78352 Jouy-en-Josas, France, 2Faculty 
of Applied Biological Science, Gifu University, 501-1193 Gifu, Japan, 3Génétique Cellulaire, Institut National de la Recherche Agronomique, 
Centre de Toulouse, 31326 Castanet-Tolosan, France, 4Unité Expérimentale de Génétique Avicole, Institut National de la Recherche Agronomique, 
Centre de Tours, 37380 Nouzilly, France and 5Département de Génétique Animale, Institut National de la Recherche Agronomique, Centre de 
Jouy, 78352 Jouy-en-Josas, France
Email: Francis Minvielle* - minvielle@dga2.jouy.inra.fr; Boniface B Kayang - bbkayang@ug.edu.gh; Miho Inoue-Murayama - miho-i@cc.gifu-
u.ac.jp; Mitsuru Miwa - j4111028@guedu.cc.gifu-u.ac.jp; Alain Vignal - vignal@autan.toulouse.inra.fr; 
David Gourichon - gouricho@tours.inra.fr; André Neau - andre.neau@jouy.inra.fr; Jean-Louis Monvoisin - jean-
louis.monvoisin@dga.jouy.inra.fr; Shin'ichi Ito - ito-s@cc.gifu-u.ac.jp
* Corresponding author    
Abstract
Background: The Japanese quail (Coturnix japonica) is both an animal model in biology and a commercial
bird for egg and meat production. Modern research developments with this bird, however, have been
slowed down by the limited information that is available on the genetics of the Japanese quail. Recently,
quail genetic maps with microsatellites and AFLP have been produced which open the way to comparative
works with the chicken (Gallus gallus), and to QTL detection for a variety of traits. The purpose of this
work was to detect for the first time QTL for commercial traits and for more basic characters in an F2
experiment with 434 female quail, and to compare the nature and the position of the detected QTL with
those from the first chicken genome scans carried out during the last few years.
Results: Genome-wide significant or suggestive QTL were found for clutch length, body weight and feed
intake on CJA01, age at first egg and egg number on CJA06, and eggshell weight and residual feed intake
on CJA20, with possible pleiotropy for the QTL affecting body weight and feed intake, and egg number
and age at first egg. A suggestive QTL was found for tonic immobility on CJA01, and chromosome-wide
significant QTL for body temperature were detected on CJA01 and CJA03. Other chromosome-wide
significant QTL were found on CJA02, CJA05, CJA09 and CJA14. Parent-of-origin effects were found for
QTL for body weight and feed intake on CJA01.
Conclusion: Despite its limited length, the first quail microsatellite map was useful to detect new QTL
for rarely reported traits, like residual feed intake, and to help establish some correspondence between
the QTL for feed intake, body weight and tonic immobility detected in the present work and those
reported on GGA01 in the chicken. Further comparative work is now possible in order to better estimate
Published: 08 June 2005
BMC Genomics 2005, 6:87 doi:10.1186/1471-2164-6-87
Received: 15 February 2005
Accepted: 08 June 2005
This article is available from: http://www.biomedcentral.com/1471-2164/6/87
© 2005 Minvielle et al; licensee BioMed Central Ltd. 
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), 
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Page 1 of 9
(page number not for citation purposes)
and understand the genetic similarities and differences of these two Phasianidae species.
BMC Genomics 2005, 6:87 http://www.biomedcentral.com/1471-2164/6/87
Background
Like the chicken, the Japanese quail belongs to the Pha-
sianidae family [1]. In the wild, it is a small migratory bird
originating from the Far East which was first raised in bird
cages in Japan and China around the 15th century because
of its singing abilities, and later became to be known in
Japan as a good egg-laying bird for human consumption
[1]. Exported to North America in the 1930s, it started to
be used for pilot studies in genetics and physiology and in
avian research [2]. The Japanese quail is now a well estab-
lished animal model in biology and a bird used for inten-
sive egg and meat production mainly in Asia and Europe,
but also in the Middle East and America [3].
Until recently, however, only a few linkage groups have
been known for the Japanese quail, and few genes have
been mapped [4] despite the large variety of traits that
have been studied in the Japanese quail [3]. The develop-
ment of the first microsatellite [5] and AFLP [6] panels
and of the corresponding maps [6,7] have made it possi-
ble to localize new genes [8,9], which should further
enhance the interest of the quail in biological research and
open the way to more comparative genetic studies with
chickens. Maps can also be used to do a genome-wide
search for quantitative trait loci (QTL) by locating QTL
nearby anonymous AFLP or microsatellite markers in seg-
regating backcross or F2 populations. Moreover, the exist-
ence of markers that cross-amplify quail and chicken DNA
[5,8] makes it possible to connect both maps and to com-
pare the QTL results for these two species, thereby getting
further insight into their evolutionary relationship.
The objective of the present work was to produce the first
set of QTL detected in Japanese quail for growth, egg pro-
duction and quality, feed consumption and other traits.
For that purpose, an F2 experiment was carried out with
two quail lines selected for early egg production [10] and
for high duration of tonic immobility [11]. The microsat-
ellite map [7] used for the detection of QTL in the present
work was developed earlier from the same F2 individuals.
Results
Overall performances
Table 1 shows the number of observations, the mean, the
standard deviation and the range of values for the traits
recorded on the 434 F2 females of the experiment.
QTL analysis
Table 2 shows the location of the significant QTL, their
position on the chromosome, the maximum F value
obtained at this position, their genetic effects, the reduc-
tion of the residual variance obtained by fitting a QTL at
this location, and the corresponding chromosome-wide
and genome-wide significance levels.
Out of the 18 QTL found to be chromosome-wide signif-
icant (pc < 0.05) on 8 of the 12 autosomes scanned in this
work, 7 were genome-wide significant (pg < 0.05), and 4
were genome-wide suggestive (pg < 0.10). Genome-wide
significant QTL for early (BW1) and late (BW2) measures
of body weight were only found on CJA01, but there was
a chromosome-wide significant QTL for BW1 on CJA02
and on CJA09, and for BW2 on CJA14. Significant QTL
were found for feed intake (FI) on CJA01 and for FI and
residual feed intake (RFI) on CJA20. Genome-wide signif-
icant or suggestive QTL for egg production characters were
obtained, on CJA01 for clutch length (CL), and on CJA06
for total egg number (EN) and age at first egg (AFE). There
Table 1: Elementary statistics on the characters measured for the 434 F2 female Japanese quail of the genome scan
Trait1 N Mean Standard deviation Minimum Maximum
TI (s) 434 177.8 86.3 17.0 300.0
BT (C) 434 41.67 0.36 40.70 43.20
BW1 (g) 434 189.0 16.8 146.6 238.8
FI (g/d) 321 27.4 2.8 18.9 35.8
RFI (g/d) 321 0.0 1.8 -4.2 7.5
EW (g) 323 11.9 1.1 9.1 15.3
YW (g) 323 3.0 0.4 2.1 5.2
SW (g) 323 0.88 0.09 0.66 1.25
Y/A (%) 323 41 5 31 78
AFE (d) 429 44.2 5.2 37 87
EN 363 322.4 72.8 18 415
CL (d) 363 7.9 4.1 1.3 47.9
BW2 (g) 352 271.0 30.4 185.0 361.0
1: TI = tonic immobility at 8–9 days of age; BT = rectal temperature at 5 weeks of age; BW1 = 5-wk body weight; FI = feed intake at 30 weeks of 
age; RFI = residual feed intake at 30 weeks of age; EW = egg weight at 30 weeks of age; YW = yolk weight; SW = eggshell weight; Y/A = ratio of 
yolk weight over albumen weight; AFE = age at first egg; EN = number of eggs laid until the age of 69 weeks; CL = clutch length; BW2 = 70-wk body Page 2 of 9
(page number not for citation purposes)
weight.
BMC Genomics 2005, 6:87 http://www.biomedcentral.com/1471-2164/6/87
were QTL for eggshell weight (SW) on CJA01 and CJA20,
and some evidence for another one on CJA05. One
genome-wide suggestive QTL was found for tonic immo-
bility (TI) on CJA01, and there was marginal evidence of
In most cases, the genetic effect was additive and negative,
indicating that the QTL allele with the lowest additive
effect originated from Line DD. The few exceptions were
for QTL on CJA06 and CJA09. Among genome-wide sug-
Table 2: Chromosomal location, test statistic (F), genetic effects and significance of the QTL detected in the Japanese quail
Chromosome 
(map length cM)
Trait1 Position 
(cM)
Flanking 
markers
F Additive 
effect ± SE
Dominance 
effect ± SE
Reduction 
of σ2 (%)
Chromosome-
Wide Probability
Genome-Wide
Probability Level
CJA01 (206) CL 0 GUJ0055 9.9 -0.93 ± 
0.36
-1.81 ± 0.58 4.9 0.0006 0.002 very 
significant
BW2 18 GUJ0055-
GUJ0052
11.6 -1.29 ± 
0.27
ns2 5.7 0.0002 0.0005 very 
significant
BW1 19 GUJ0052 5.9 -4.36 ± 
1.38
ns 2.3 0.034 0.09 suggestive
FI 19 GUJ0052 8.3 -1.03 ± 
0.26
ns 4.4 0.004 0.01 significant
TI 91 ADL0037 6.2 -20.3 ± 6.3 ns 2.5 0.034 0.09 suggestive
BT 180 GUJ0062 5.7 -0.088 ± 
0.026
ns 2.5 0.047 0.12 ns
SW 191 GUJ0062-
GUJ0068
7.2 -0.027 ± 
0.009
-0.030 ± 
0.0134
3.4 0.016 0.04 significant
CJA02 (61) BW1 54 GUJ0063-
GUJ0027
4.6 ns 7.42 ± 2.75 1.7 0.038 0.29 ns
CJA03 (38) BT 1 GUJ0099 6.1 -0.090 ± 
0.029
ns 2.5 0.008 0.11 ns
CJA05 (21) SW 12 GUJ0049 5.5 -0.026 ± 
0.008
ns 2.3 0.012 0.27 ns
CJA06 (74) EW 0 GUJ0021 5.4 0.330 ± 
0.100
ns 2.7 0.023 0.16 ns
EN 32 GUJ0087 7.0 21.6 ± 6.1 ns 3.3 0.006 0.04 significant
AFE 34 GUJ0087-
GUJ0054
6.2 -1.52 ± 
0.46
ns 2.9 0.012 0.09 suggestive
CJA09 (25) BW1 25 GUJ0071 4.3 3.34 ± 1.22 ns 1.6 0.028 0.46 ns
CJA14 (8) BW2 7 GUJ0023-
GUJ0097
6.2 ns -1.32 ± 0.38 2.9 0.004 0.24 ns
CJA20 (25) FI 2 GUJ0065-
GUJ0083
8.5 -0.883 ± 
0.231
ns 4.5 0.001 0.02 significant
SW 21 GUJ0065-
GUJ0083
6.7 -0.026 ± 
0.008
0.024 ± 
0.013
3.4 0.003 0.06 suggestive
RFI 25 GUJ0083 7.2 -0.525 ± 
0.142
ns 3.8 0.002 0.04 significant
1: CL = clutch length (d); BW2 = 70-wk body weight (g); BW1 = 5-wk body weight (g); FI = feed intake at 30 weeks of age (g/d); TI = tonic 
immobility at 8–9 days of age (s); BT = rectal temperature at 5 weeks of age(C); SW = eggshell weight at 30 weeks of age (g); EW = egg weight (g); 
EN = egg number until the age of 69 weeks; AFE = age at first egg (d); RFI = residual feed intake at 30 weeks of age (g/d).
2: ns = not significant.Page 3 of 9
(page number not for citation purposes)
QTL for egg weight (EW) on CJA06, and for body temper-
ature (BT) on CJA01 and CJA03.
gestive and significant QTL, dominance was only signifi-
cant for CL and SW. The reduction of the residual variance
BMC Genomics 2005, 6:87 http://www.biomedcentral.com/1471-2164/6/87
due to fitting a QTL was moderate and did not exceed
5.7%.
Chromosome CJA01
Interval mapping results for CJA01 are shown in Table 2
and Figure 1. For all traits, the allele received from the Line
DD ancestry decreased the additive genotypic value. The
QTL for BW1, BW2 and FI were found at very close posi-
tions, the QTL for TI was obtained in the middle of the
interval near the chicken microsatellite ADL0037, and the
other QTL were placed at both ends of the chromosome.
Chromosome CJA06
Interval mapping results for CJA06 are shown in Table 2
and Figure 2. The QTL for EN and AFE were found in the
middle of the chromosome at very close positions. Both
alleles received from the Line DD were favourable for egg
production, with a positive additive effect on EN and a
negative one on AFE.
Chromosome CJA20
Interval mapping results for CJA20 are shown in Table 2.
In this short linkage group, the QTL for FI and RFI were
found at opposite ends but, for both traits, the allele
decreasing the additive value was transmitted by the Line
DD.
Imprinting and two-QTL alternative
Imprinting (parent-of-origin effect) was estimated for
genome-wide significant QTL. It was only found to be sig-
nificant for BW1 (Fs = 9.0 > F.01 [1,415] = 6.7) and FI (Fs = 7.6
> F.01 [1,318] = 6.7), on CJA01, with a larger effect (5.7 ± 1.4
g and 0.73 ± 0.25 g, respectively) for sire-transmitted alle-
les. Similarly, the two-QTL hypothesis was tested, but
there was no evidence for two different QTL located on
the same linkage group and acting simultaneously on the
same trait.
Discussion
Method
Interval mapping of QTL on chromosome CJA01Figure 1
Interval mapping of QTL on chromosome CJA01. Only traits with a QTL detected on CJA01 are shown. Significance 
thresholds varied little between traits, so unique genome-wide suggestive (p < 0.10), significant (p < 0.05) and very significant (p 
< 0.01) thresholds are indicated by horizontal dashed or continuous lines. The positions of the markers are indicated by red 
stars.
0
2
4
6
8
10
12
1 13 25 37 49 61 73 85 97 109 121 133 145 157 169 181 193 205
Position (cM)
Va
ria
nc
e
ra
tio
(F
)
Body weight
Body temperature
Tonic immobility
Clutch length
End body weight
Feed intake
Egg shell weight
very significant
significant
suggestivePage 4 of 9
(page number not for citation purposes)
The line-cross model used for QTL detection assumes that
different QTL were fixed in the Lines DD and LTI [12].
BMC Genomics 2005, 6:87 http://www.biomedcentral.com/1471-2164/6/87
This hypothesis could not be checked, but bandsharing
(BS) between the two quail origins was low (0.19) [13]
and similar to that between highly divergent poultry lines
of broilers and layers [14], suggesting that the departure
from the ideal situation of fixation in the parental lines
was limited. Moreover, the main consequence of starting
from outbred F0 lines would only be to underestimate the
QTL effects [15]. This might partly explain the relatively
small reduction of residual variance observed (see Table
2) for significant QTL under the full model. Using a more
general approach with full/half sib models [16] was also
possible, but it would have required larger full-sib fami-
lies [17] in order to accurately estimate the larger number
of parameters needed with those models.
QTL effects
weight and feed consumption QTL, the negative sign of
the additive effects indicated that favourable alleles
(increasing body weights and decreasing FI and RFI) orig-
inated from Line DD, in agreement with the results of the
zootechnical comparison between the two lines at the F0
generation of the present experiment [18]. The situation
was similar for the QTL found for EN (positive difference)
AFE (negative difference) and SW (negative difference),
since Line DD was a better laying line but with lower egg
(and eggshell) weight. Surprisingly, however, the best
allele for the very significant QTL found for CL was trans-
mitted by Line LTI, although its average clutch length was
1.1 d shorter than that of Line DD in the F0 generation
[18]. Of course, an inferior line may possess superior alle-
les as first evidenced in early tomato QTL studies [19].
Also, this QTL had a larger dominance effect (see Table 2),
Interval mapping of QTL on chromosome CJA06Figure 2
Interval mapping of QTL on chromosome CJA06. Only traits with a QTL detected on CJA06 are shown. Significance 
thresholds varied little between traits, so unique genome-wide suggestive (p < 0.10) and significant (p < 0.05) thresholds are 
indicated by horizontal dashed lines. The positions of the markers are indicated by red stars.
0
1
2
3
4
5
6
7
8
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71
Position (cM)
V
a
r
i
a
n
c
e
r
a
t
i
o
(
F
)
Age at first egg
Egg number
significant
suggestivePage 5 of 9
(page number not for citation purposes)
The additive effects listed in Table 2 estimated the differ-
ences between Line DD and Line LTI alleles. For body
which could not be forecasted from information on the
pure lines. It is also possible, however, that its localisation
BMC Genomics 2005, 6:87 http://www.biomedcentral.com/1471-2164/6/87
at one end of the linkage group and its effect were some
artefact related to the significant segregation distortion
observed at this position. The QTL allele originating from
the LTI line selected for extreme duration of tonic immo-
bility [11] also increased TI in the F2 population. Its posi-
tion on CJA01 confirmed the result obtained for TI in
another F2 experiment on the Japanese quail carried out
to detect stress-related traits using AFLP markers [9]. To
our knowledge, the location of a significant QTL for resid-
ual feed intake in layers is the first one in a poultry species.
The QTL was located on a microchromosome with few
markers, however, and it will need to be confirmed in
independent genome scans, but it is already an interesting
starting point for further work. Finally, it was not surpris-
ing that the QTL for BT were only chromosome-wide
significant in this medium-sized experiment because
body temperature is highly regulated and shows very little
variation (see Table 1), but quantitative genetic variation
for BT has already been reported in the chicken [20], and
confirmation of these QTL would represent a very signifi-
cant finding.
Co-location of QTL
It is likely that the QTL for BW2, BW1 and FI, located at 18
and 19 cM on CJA01, represent a single gene. Indeed,
body weight and feed intake are known to be highly cor-
related genetically (0.5 to 0.9) in poultry [21], and the
rank correlation between BW1 and FI was 0.5 (p < 0.01)
in the F2. It is worth noting, however, that the suggestive
QTL found for TI on the same chromosome was not
placed near any other significant QTL. This observation
was in good agreement with the absence of association
between TI and all the other traits reported from factorial
correspondence analysis of the same F2 data [22]. There-
fore, the association between stress susceptibility and pro-
duction in the quail, if it exists, is not mediated
significantly by major genes involved in the determinism
of the duration of tonic immobility measured at a young
age.
The only other instance of close location of two QTL was
for EN and AFE at 32 and 34 cM on CJA06, but the rank
correlation between them was only -0.1 (p < 0.05) in the
F2, which does not strongly suggest that there might be
also a single pleiotropic QTL at this position.
Unfortunately, pleiotropy could not be tested with the
software presently available.
Comparison with chicken QTL
Several recent reports of genome-wide scans in the
chicken have described QTL for body weight [23-30], feed
intake [23,25,27], egg production traits [25,27,28] and
found for RFI in broilers on GGA01, GGA04 and GGA05,
however, but in studies [32,33] which were focused on
some specific chromosomal regions.
Significant QTL for body weight in the chicken were only
reported repeatedly on GGA01 [23,24,26,27,30], homol-
ogous to CJA01, and on GGA04 [25,28,32]. Moreover, in
two out of the three chicken studies where both BW and
FI were measured, QTL were found at the same position
for body weight and feed intake on GGA01 [23,27], as on
CJA01 in the present work. In the third report [25], despite
the varied nature of the traits which were studied, no QTL
was found at all on GGA01, but QTL which affected BW
and TI were detected in the same region of GGA04. In our
work, however, no QTL was found on CJA04. Overall,
then, the largest chicken and quail chromosomes might
contain an important and homologous QTL for growth.
Regarding QTL for egg production in layers, none were
found on GGA06 which is homologous to CJA06 on
which QTL for EN and AFE have been detected in this
work. But egg production is a complex trait because egg
laying evolves with time, and it was only measured over a
limited period in the works on the chicken, so the charac-
ters were not directly comparable.
The location of a QTL for tonic immobility on two homol-
ogous chromosomes in chicken [31] and quail suggests
that the duration of tonic immobility, a trait associated to
fear response [11], is, at least partly, under a similar
genetic determinism in the two species. The associations
found between QTL for TI and QTL for growth and egg
weight on GGA01 in the red jungle fowl layer intercross
[31], however, contradict the lack of association reported
in our quail QTL experiment in the present paper, and
reported in previous phenotypic analyses [18,22].
Some parent-of-origin effects were recently reported in the
chicken [34]. They were detected mainly on GGA01, and
some were found for QTL for body weight and feed intake,
as in the present study. It is rather unlikely that these con-
verging results obtained independently in two species
from the family Phasianidae were only coincidental. Con-
sequently, they should raise some interest in looking fur-
ther for this type of effect in avian species (where
reciprocal effects are common), and, more generally, for
possible imprinting-like mechanisms in Birds [34].
Possible candidate genes
Of course, only chromosomal regions could be detected
in this study, but it is interesting to note that in the
chicken, the gene for the insulin-like growth factor IA
associated with growth [35], and the gene for a receptor of
serotonin which might be implicated in behaviour [36]Page 6 of 9
(page number not for citation purposes)
tonic immobility [31], but none was found for body tem-
perature and residual feed intake in layers. A QTL was
are on GGA01 http://www.ncbi.nlm.nih.gov/mapview/,
whereas we found a QTL for body weight and one for
BMC Genomics 2005, 6:87 http://www.biomedcentral.com/1471-2164/6/87
tonic immobility on the homologous quail chromosome
CJA01. In the same way, the agouti gene is linked to feed
intake [37], and a QTL for feed intake was detected on
CJA20 where an agouti-like locus was mapped in the Jap-
anese quail [8]. These chromosomal co-locations are only
indicative, but they might deserve to be explored further.
Conclusion
For the first time with the Japanese quail, a partial genome
scan using microsatellites has revealed genome-wide sig-
nificant QTL for major production-related traits (BW, FI,
CL, EN), and QTL for other traits with wider potential
interest (TI, RFI, BT) were also detected. Few results for
traits measured on both the quail and chicken are availa-
ble, and comparisons between the two species are only at
the beginning, but the common co-location (CJA01 and
GGA01) of QTL acting on BW and FI, and of QTL for TI
are already indicative of the detailed genetic similarity
between the two species that future comparative work
should further explore. Of course, only chromosomal
regions could be detected in this study, but it is interesting
to note that in the chicken, the gene for the insulin-like
growth factor associated with growth and the gene for the
serotonin 1F receptor implicated in behavioral traits are
on GGA01, whereas a QTL for body weight and one for
tonic immobility were found on CJA01. In the same way,
the agouti gene is linked to feed intake, and a QTL for feed
intake was detected on CJA20 where an agouti-like locus
was just mapped in the Japanese quail.
Methods
Birds and Husbandry
Two lines, LTI and DD, with different origins [13] and
selected respectively for high duration of tonic immobility
[11] and for early egg production [10] were crossed recip-
rocally (12 single-pair matings) to produce F1 quail. All
LTI breeders had a maximum duration (300 s) of experi-
mental tonic immobility, and a maximum value for TI
was 55 s in Line DD. Ten males and 30 egg-laying females
were drawn randomly across F1 families to produce the F2
generation. The duration of TI in the F1 breeding group
varied between 31 and 300 s. Each F1 sire was mated to
three full sisters from another F1 family, and 30 F2 full-sib
families were produced in three consecutive hatches to
obtain the 434 female quail studied in the present work,
with 39 to 45 F2 birds per sire family and 12 to 19 quail
per full-sib F2 family.
F2 quail were successively given standard starter and com-
mercial layer diets [10]. At 5 wk of age they were assigned
at random to individual cages of a 4-tier battery main-
tained at 25°C, and in which they remained until the end
of the experiment, with free access to feed and drinking
Traits
The traits will be described chronologically. The duration
of TI was measured for up to 5 min at 8 or 9 days of age.
TI was the length of time during which a chick remained
immobile after the freezing reaction had been induced by
keeping it gently on its back for 10 s. Body weight (BW1)
and rectal body temperature (BT) were measured at 5
weeks of age. Egg production was recorded daily and indi-
vidually from 5 to 69 weeks of age. Age at first egg (AFE),
total egg number (EN) and clutch length (CL: average
number of consecutive days with an egg) were obtained
from the egg laying data. A 24 day feed trial was con-
ducted on 30-wk females fed ad libitum. Individual daily
intake was recorded, and total residual feed intake was
estimated for each bird as the residual of the multiple
regression of total feed intake on mean metabolic body
weight, body weight gain and egg mass produced on test
[22]. Observed and residual intake values were then
divided by 24 to obtain FI and RFI. RFI is a relative value
which represents the daily amount of feed used for non-
productive traits (activity, basal metabolism, heat incre-
ment). It is an important character for production pur-
poses but also for more fundamental metabolic studies.
Egg weight (EW) and gross composition (YW: yolk
weight, SW: eggshell weight; Y/A: ratio of yolk weight over
albumen weight) were obtained from three consecutive
eggs per quail collected around 30 weeks of age for each
quail. Finally, body weight was measured again at 70
weeks of age (BW2). Statistical analyses were run with
untransformed data for all characters, except for tonic
immobility which was also analysed as log(1+TI), and
produced the same results as for TI.
Genotyping
All 24 F0, 40 F1 and 434 F2 quail in the present experi-
ment belonged to the resource family set up to establish
the first microsatellite quail map [7], and they had all
been typed previously for the microsatellites listed in the
augmented microsatellite panel [5]. Genotyping was car-
ried out at the Gifu University, and genotypic data were
arranged, validated and stored in the MAPGENA database.
Mean heterozygosity of the 10 F1 sires was 61%. The map
had been built from 72 microsatellite loci, and 58 of them
had been resolved into 13 linkage groups, including a Z
chromosome group, for a total map distance of 576 cM
with a 10 cM average spacing between loci [7]. At that
time, only seven of the linkage groups could be assigned
to chromosomes CJA01, CJA02, CJA05, CJA06, CJA14,
CJA27 and CJAZ through comparative mapping with the
chicken. Since then, however, all other linkage groups in
the microsatellite map were assigned to other chromo-
somes [Kayang et al., unpublished data; [8]]. Conse-
quently, the remaining linkage groups Q03, Q04, Q08,Page 7 of 9
(page number not for citation purposes)
water. Q09, Q10 and Q11 in the original article [7] have been
BMC Genomics 2005, 6:87 http://www.biomedcentral.com/1471-2164/6/87
renamed respectively, CJA03, CJA13, CJA09, CJA04,
CJA20 and CJA10 in the present one.
QTL analyses
QTL detection was performed using the line cross method
[12] implemented in the QTL Express software [38].
Briefly, for each trait independently, an analysis of regres-
sion was carried out along each autosome to test for the
effect of a putative QTL. In the present study, the linear
model also included a hatch effect (3 classes) for all traits,
and a technician effect (2 classes) for TI, so an analysis of
covariance was carried out. The most likely position of the
QTL corresponded to that found with the maximum F
value. Five thousand permutations [39] were then carried
out to set significance levels (pc) for the most likely chro-
mosome-wide QTL. Finally, genome-wide significance
(pg) for a QTL detected on a given chromosome was
obtained from pc by: pg = 1-(1-pc)1/r, where r was the ratio
of the length of this chromosome over the total chromo-
some length (545 cM) spanned by the present study.
Chromosome-wide significance was set up conservatively
at pc = 0.05. Genome-wide significant and suggestive
thresholds were set up respectively at pg = 0.05 and 0.10.
A significant (p < 0.05) segregation distortion was found
only near the 0 position on CJA01.
Authors' contributions
FM designed and coordinated the study, and wrote the
paper. BBK, SI, MIM and MM designed, organized, and
conducted all the microsatellite work. AV led the mapping
part. AN was responsible for the data bank, and DG and
JLM supervised and carried out the data collection.
Acknowledgements
The authors dedicate this article to the memory of Dr Andrew Mills who 
developed the LTI Japanese quail line with JM Faure at INRA in Nouzilly 
(France). His determination and devotion to research have produced a 
unique bird model that we dearly thank him for.
The authors wish to thank JM Faure (INRA-SRA, Nouzilly) for kindly pro-
viding F0 birds of Line LTI. Expert care of experimental F0, F1 and F2 quail, 
and data collection by C Moussu and the team at the INRA Unité Expéri-
mentale de Génétique Avicole (Nouzilly, France) are gratefully acknowl-
edged. The linguistic revision of the paper was kindly carried out by W 
Brand-Williams.
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