ArticlePDF Available

Genetic variation in pure lines and crosses of large-bodied turkey lines. 3. Growth-related measurements on live birds

Authors:

Abstract

An experimental line (F) selected over 34 generations for increased 16-wk BW was reciprocally crossed with a primary breeding sire line (C) from a large international turkey breeder to study the inheritance of growth-related traits measured on live birds. All genetic groups were grown intermingled in confinement with sexes reared in different houses. The traits measured included BW at 8, 16, and 20 wk of age and shank length, shank width, shank depth, breast width, and walking ability scores at 16 wk of age. Walking ability was rated from 1 to 5 with 1 representing birds with no leg defects and no difficulty walking and 5 indicating birds with extreme lateral deviations of the legs and great difficulty walking. Ratings of 2, 3, and 4 represented intermediate values. The F line had a different growth pattern than the C line with the F line being larger than the C line at 8 wk of age, but the reverse was true at 16 and 20 wk of age. The difference in BW between the C and F lines increased from 16 to 20 wk of age. The C line had wider breasts than the F line at 16 wk of age. The F line had longer shanks than the C line. Shank width was larger in the C line than the F line for females but not males. No line difference in shank depth was observed. Walking ability scores at 16 wk of age were lower (better) in the C line than in the F line for males but not females. Significant heterosis in BW of the crosses of the F and C lines was observed at all ages in males (range = 3.3 to 5.6%) and only at 8 wk of age in females (3.6%). These results were similar to an earlier study in which the F line was crossed with a primary-breeding sire line from 2 other international turkey breeders. No significant heterosis in the crosses of the C and F line was observed for breast width and shank measurements. Heterosis was significant for walking ability scores of females (-3.0%) but not males. Reciprocal effects, a measure of sex linkage and maternal influences, were noted only for shank length and the direction of the difference was not the same in the 2 sexes.
GENETICS
Genetic Variation in Pure Lines and Crosses of Large-Bodied Turkey Lines.
3. Growth-Related Measurements on Live Birds
1
K. E. Nestor,
2
J. W. Anderson, and S. G. Velleman
Department of Animal Sciences, Ohio Agricultural Research and Development Center,
The Ohio State University, Wooster, Ohio 44691
ABSTRACT An experimental line (F) selected over 34
generations for increased 16-wk BW was reciprocally
crossed with a primary breeding sire line (C) from a large
international turkey breeder to study the inheritance of
growth-related traits measured on live birds. All genetic
groups were grown intermingled in confinement with
sexes reared in different houses. The traits measured in-
cluded BW at 8, 16, and 20 wk of age and shank length,
shank width, shank depth, breast width, and walking
ability scores at 16 wk of age. Walking ability was rated
from 1 to 5 with 1 representing birds with no leg defects
and no difficulty walking and 5 indicating birds with
extreme lateral deviations of the legs and great difficulty
walking. Ratings of 2, 3, and 4 represented intermedi-
ate values.
The F line had a different growth pattern than the C
line with the F line being larger than the C line at 8 wk
of age, but the reverse was true at 16 and 20 wk of age.
The difference in BW between the C and F lines increased
from 16 to 20 wk of age. The C line had wider breasts
(Key words: turkey, body weight, breast width, inheritance, walking ability score)
2005 Poultry Science 84:1341–1346
INTRODUCTION
Commercial turkey breeders have made major im-
provements in growth characteristic of the modern turkey
(Havenstein et al., 2004a,b). Because commercial turkeys
are the result of a cross of a sire line (or sire line cross)
and a dam line (or dam line cross), the genetic gains could
be due to improvements within the primary breeding
lines (additive genetic variation) or heterosis (nonaddive
genetic variation) in the crosses used to produce the com-
mercial turkey.
Additive genetic variation is an important source of
variation for growth traits in turkeys. It has been shown
2005 Poultry Science Association, Inc.
Received for publication February 24, 2005.
Accepted for publication May 9, 2005.
1
Salaries and research support provided by state and federal funds
appropriated to the Ohio Agricultural Research and Development Cen-
ter, The Ohio State University.
2
To whom correspondence should be addressed: Nestor.1@osu.edu.
1341
than the F line at 16 wk of age. The F line had longer
shanks than the C line. Shank width was larger in the C
line than the F line for females but not males. No line
difference in shank depth was observed. Walking ability
scores at 16 wk of age were lower (better) in the C line
than in the F line for males but not females.
Significant heterosis in BW of the crosses of the F and
C lines was observed at all ages in males (range = 3.3 to
5.6%) and only at 8 wk of age in females (3.6%). These
results were similar to an earlier study in which the F
line was crossed with a primary-breeding sire line from
2 other international turkey breeders. No significant het-
erosis in the crosses of the C and F line was observed for
breast width and shank measurements. Heterosis was
significant for walking ability scores of females (3.0%)
but not males. Reciprocal effects, a measure of sex linkage
and maternal influences, were noted only for shank length
and the direction of the difference was not the same in
the 2 sexes.
that large gains in BW (McCartney et al., 1968; Nestor,
1977, 1984; Nestor et al., 1996), breast width (Nestor et
al., 1969), and shank width (Nestor et al., 1985) can be
made by genetic selection within lines.
In general, earlier research suggested that nonadditive
genetic variation was not a major contributor to total
genetic variation for growth traits of turkeys. In earlier
studies, heterosis for BW was observed in some crosses
(Asmundson, 1942, 1948; Jerome et al., 1960; Friars et al.,
1963) but not in other crosses (Knox and Marsden, 1944;
Kondra and Shoffner, 1955; Jerome et al., 1960; Clark,
1961; Nestor, 1971). In some cases, heterosis was observed
only for BW at certain ages (Asmundson and Pun, 1954;
Friars et al., 1963). With diallel crosses, McCartney and
Chamberlin (1961) concluded that additive genetic vari-
ance was much more important that nonadditive genetic
variance for BW and body conformation measurements.
Abbreviation Key: A, B, C, and N lines = commercial sire lines; F =
experimental line selected long term for increased 16-wk BW; and FL =
subline of F selected for increased shank width.
NESTOR ET AL.1342
More recent studies suggest that nonadditive genetic
variation is an important source of variation in growth
traits, particularly in offspring of crosses of lines differing
greatly in growth rate and body conformation. Emmerson
et al. (1991) observed significant heterosis for BW at older
ages and shank length in F
1
reciprocal crosses of an experi-
mental line (F) selected long term for increased 16-wk
BW and a commercial sire line (N) no longer in commer-
cial use. No heterosis for BW was observed in a cross of
an experimental egg line and the F line at 8, 16, or 20 wk
of age, and heterosis was observed only at 20 wk of age
in a cross of the egg and N lines (Nestor et al., 1997).
In crosses of an experimental line (FL) selected only for
increased shank width and an unimproved commercial
sire line, Ye et al. (1997) observed significant heterosis for
BW and shank length. When the FL line was crossed with
2 improved commercial sire lines (A and B), significant
heterosis in BW was observed for females of the cross
involving line A and for males of the cross involving line
B (Nestor and Anderson, 1998). When the F line was
crossed with commercial sire lines A and B, heterosis was
an important source of variation in BW of males and
percentage heterosis ranged from 3.1 to 7.5 (Nestor et al.,
2001a). For females of the reciprocal crosses of the F and
commercial sire lines, heterosis (range = 2.6 to 4.9%) was
only significant at younger ages (8 wk for the crosses of
the A and F lines and 8 and 16 wk for the crosses of the
B and F lines). At 16 wk of age, no significant heterosis
was observed for breast width and heterosis was sporadic
for shank measurements. The purpose of the present
study was to evaluate genetic variation of BW, breast
width, shank measurements, and walking ability in pure
lines and reciprocal crosses of the F and a sire line (C)
from a third major international turkey breeder.
MATERIALS AND METHODS
Genetic Stocks
The F line was started from a randombred control pop-
ulation by mass selection only for increased 16-wk BW.
Details of the maintenance of the F line and response to
selection have been previously reported (Nestor, 1977,
1984; Nestor et al., 1996, 2000). The F line had been se-
lected for 34 generations at the time of the study. A sample
of a sire line C was obtained from a major international
breeder as unpedigreed eggs.
Offspring from the pure F and C lines and reciprocal
crosses were produced in 2 hatches, each of which repre-
sented a 2-wk collection of eggs. The F line was produced
by weekly artificial mating of 36 sires to 72 dams with
each sire being mated to 2 dams. The number of offspring
produced was 262 males and 306 females. The pure C
line was produced from 20 dams artificially mated to 12
sires. Each week, the sire used for artificial insemination
of each hen was changed so that as large a genetic base
as possible was obtained. The number of offspring for
the C line was 50 males and 58 females. To produce the
cross involving F-line sires and C-line dams, the sires
were the same ones used in producing the pure F line,
and a different F-line sire was used to inseminate each
of 20 dams weekly in a manner so that all 36 F-line sires
were involved in the production of the cross. For the
reciprocal cross, 20 F-line dams were used and the same
sires used to produce the pure C line were also used in
the production of the crosses. The sire assigned to each
hen was changed weekly to insure as wide a genetic base
as possible. The number of offspring for the reciprocal
crosses ranged from 40 to 60 within each cross and sex
subgroup with an average of 48.8.
Management of Birds
and Measurements Made
Offspring from the pure lines and reciprocal crosses
were grown intermingled in confinement with the sexes
reared in separate houses. All birds were provided a de-
clining protein 5-ration system (Naber and Touchburn,
1970) based on the schedule for males. Continuous light-
ing was provided from hatching to 6 wk of age, when
the photoperiod was reduced to 12 h per day. At 16 wk
of age, the amount of light per day was reduced to 10 h
and remained at this level until 20 wk of age.
Body weight was recorded at 8, 16, and 20 wk of age.
At 16 wk of age, measurements of shank length, shank
width (laterally at the dew claw), shank depth (perpendic-
ular at the dew claw), and breast width were made. Breast
width was measured at 6.35 cm of body depth at a point
approximately 3.18 cm from the anterior point of the keel.
Walking ability at 16 wk of age was estimated by the
same person using the method of Nestor et al. (1985)
in which each bird was given a score of 1 to 5, with 1
representing birds with no leg defects and no difficulty
walking and 5 indicating birds with extreme lateral devia-
tions of the legs and great difficultly walking. Ratings of
2, 3, and 4 represented intermediate values.
Statistical Analysis
The data were analyzed using the GLM procedure of
SAS (SAS Institute, 1988) with genetic group (pure lines
and reciprocal crosses), sex, hatch, and the interaction of
genetic group and sex as source of variation. Orthogonal
contrasts (SAS Institute, 1988) were used to estimate addi-
tive genetic effects (contrast of F and C), heterotic effects
(contrast of average of the parental lines with the average
of the reciprocal crosses), and sex-linked and maternal
effects (contrast of reciprocal crosses). Percentage of heter-
osis was obtained by dividing the difference between the
average of the parental lines and that for the reciprocal
crosses by the average of the parental lines and multi-
plying by 100. Data for the 2 sexes were also analyzed
separately as above with genetic group and hatch as
sources of variation.
RESULTS
Hatch and Sex Effects
Hatch effects were significant for BW at 8 and 16 wk
of age and breast width in the analyses of the sexes sepa-
GENETIC VARIATION OF GROWTH TRAITS IN TURKEYS 1343
TABLE 1. Effect of reciprocally crossing a commercial sire line (C) and a line (F) selected
long term for increased 16-wk BW on performance of males
Parental lines Reciprocal crosses Additive
genetic Reciprocal Percentage
Variable C F F × CC× F effect
1
effect
2
heterosis
3
SEM
Body weight, kg
8 wk 4.90 5.13 5.12 5.24 *** NS 3.32** 0.120
16 wk 15.50 14.61 15.85 15.95 *** NS 5.61** 0.529
20 wk 20.47 18.84 20.41 20.85 *** NS 4.96** 1.166
Walking ability scores
4
2.43 2.85 2.35 2.53 ** NS 7.58 0.087
Shank
Length, cm 21.79 22.49 21.81 22.28 *** * 0.04 0.106
Width, mm 17.69 17.83 17.47 17.83 NS NS 0 0.115
Depth, mm 26.15 25.84 26.21 26.32 NS NS 1.04 0.113
Breast width, cm 15.43 12.65 14.16 14.04 *** NS 0.06 0.276
1
Measured by contrast of parental lines.
2
Measured by contrast of reciprocal crosses.
3
Percentage heterosis = [(average of reciprocal crosses average of parental lines)/average of parental lines]
× 100.
4
Birds were subjectively rated at 16 wk of age from 1 to 5 with 1 representing birds whose legs did not have
any defects and had no difficulty walking and 5 indicating birds whose legs exhibited extreme lateral deviations
or had great difficulty walking. Ratings of 2, 3, and 4 represented intermediate values.
*P 0.05.
**P 0.01.
***P 0.001.
rate and sexes combined and for female BW at 20 wk of
age (data not shown). In general, hatch effects were not
significant for shank measurements and walking ability
scores with the only exception being shank length of
males (data not shown). In the combined analysis, the
sex effect was highly significant (P 0.001) for all traits
with the value for males being larger than that for females
measured except for breast width (data not shown). The
interaction between genetic group and sex was significant
for BW at 16 and 20 wk of age (P 0.001), shank length
(P 0.001), and walking ability scores (P 0.01). The
interactions in all cases were the result of scaling effects.
Additive Genetic Effects
The C and F lines differed in BW at all ages for males
(Table 1), females (Table 2), and sexes combined (Table
3). At 8 wk of age, the F line was larger than the C line
but the reverse was true at 16 and 20 wk of age. The F
line had longer shanks than the C line at 16 wk of age
for males, females, and sexes combined. Shank width at
16 wk of age did not differ between lines for males, but
for females and sexes combined shank width was larger
in the C line than in the F line. Shank depth at 16 wk of
age was significantly (P 0.05) larger in the C line than
in the F line only in the combined analysis. The breast at
16 wk of age was wider in the C line than in the F line
in all analyses. Walking ability scores at 16 wk of age
were lower (birds walked better) for the C line than the
F line in males and sexes combined.
Reciprocal Effects
Reciprocal effects, a measure of sex linkage or maternal
influence, were not an important source of variation for
most traits (Tables 1 to 3). In the reciprocal crosses, the
sire is listed first. Reciprocal effects were significant (P
0.05) for shank length in the males and females when
analyzed separately but not in the combined analysis.
The direction of the difference between reciprocal crosses
was different for males than for females.
Nonadditive Genetic Variation
Heterosis of BW at 8, 16, and 20 wk of age was a more
important source of variation in the analysis of males
separately (Table 1) and for sexes combined (Table 3).
For females, heterosis was significant (P 0.01) only at 8
wk of age (Table 2). For males and for both sexes com-
bined, percentage heterosis ranged from 3.32 to 5.61 and
3.14 to 3.53, respectively, at the various ages. Heterosis
was not an important source of variation for the shank
measurements or breast width in any analysis. The recip-
rocal crosses had lower average walking ability scores
than the pure lines in all analyses with the heterosis being
significant for females (P 0.05) (Table 2) and sexes com-
bined (P 0.01; Table 3). For males (Table 1), the percent-
age heterosis was large (7.58) but not significant
DISCUSSION
The experimental F line was not closely related to pri-
mary breeding sire lines currently in use by 3 major inter-
national turkey breeders when based on DNA finger-
printing (Ye et al., 1998) or the frequency of MHC haplo-
types (Zhu et al., 1995, 1996b). In the study of Ye et al.
(1998), band sharing of DNA fingerprints was greater
among the commercial sire lines than between the F line
and commercial sire lines. One MHC class II haplotype
was predominant in all of the commercial lines (Zhu et
NESTOR ET AL.1344
TABLE 2. Effect of reciprocally crossing a commercial sire line (C) and a line (F) selected
long term for increased 16-wk BW on performance of females
Reciprocal
Additive
Parental lines crosses
genetic Reciprocal Percentage
Variable C F F × CC× F effect
1
effect
2
heterosis
3
SEM
Body weight, kg
8 wk 4.05 4.17 4.30 4.20 * NS 3.58** 0.035
16 wk 11.97 11.17 11.83 11.58 *** NS 1.17 0.068
20 wk 14.68 13.42 14.33 14.17 *** NS 1.42 0.176
Walking ability scores
4
2.30 2.22 1.99 2.20 NS NS 3.00* 0.060
Shank
Length, cm 17.75 18.15 18.04 17.79 *** * 0.02 0.046
Width, mm 16.49 15.83 16.26 16.15 *** NS 0.28 0.107
Depth, mm 22.60 22.35 22.66 22.36 NS NS 0.16 0.073
Breast width, cm 15.33 13.13 14.16 13.83 *** NS 1.65 0.103
1
Measured by contrast of parental lines.
2
Measured by contrast of reciprocal crosses.
3
Percentage heterosis = [(average of reciprocal crosses average of parental lines)/average of parental lines]
× 100.
4
Birds were subjectively rated at 16 wk of age from 1 to 5 with 1 representing birds whose legs did not have
any defects and had no difficulty walking and 5 indicating birds whose legs exhibited extreme lateral deviations
or had great difficulty walking. Ratings of 2, 3, and 4 represented intermediate values.
*P 0.05.
**P 0.01.
***P 0.001.
al., 1996b). In the F line, frequency of class II haplotypes
was more diverse (Zhu et al., 1995).
The F line apparently has a different growth pattern
than commercial sire lines. In the study of Nestor et al.
(2001a), BW at 8 wk of age of the F line was similar to,
or larger than, that from a primary breeding sire line from
2 of the 3 major international breeders but by 16 wk of
age, BW was larger in the commercial sire lines than the
F line and the line differences increased in magnitude at
20 wk of age. In the current study, the F line was larger
TABLE 3. Effect of reciprocally crossing a commercial sire line (C) and a line (F) selected
long term for increased 16-wk BW on performance of sexes combined
Reciprocal
Additive
Parental lines crosses
genetic Reciprocal Percentage
Variable C F F × CC× F effect
1
effect
2
heterosis
3
SEM
Body weight, kg
8 wk 4.48 4.65 4.71 4.71 *** NS 3.33*** 0.038
16 wk 13.88 12.90 13.84 13.78 *** NS 3.14*** 0.177
20 wk 17.57 16.14 17.38 17.54 *** NS 3.53*** 0.229
Walking ability scores
4
2.37 2.54 2.17 2.37 * NS 7.54** 0.061
Shank
Length, cm 19.76 20.32 19.93 20.04 *** NS 0.27 0.066
Width, mm 17.10 16.60 16.87 16.98 *** NS 0.45 0.096
Depth, mm 24.37 24.10 24.44 24.34 * NS 0.64 0.078
Breast width, cm 15.26 12.69 13.90 14.11 *** NS 0.03
1
Measured by contrast of parental lines.
2
Measured by contrast of reciprocal crosses.
3
Percentage heterosis = [(average of reciprocal crosses average of parental lines)/average of parental lines]
× 100.
4
Birds were subjectively rated at 16 wk of age from 1 to 5 with 1 representing birds whose legs did not have
any defects and had no difficulty walking and 5 indicating birds whose legs exhibited extreme lateral deviations
or had great difficulty walking. Ratings of 2, 3, and 4 represented intermediate values.
*P 0.05.
**P 0.01.
***P 0.001.
than the C line at 8 wk of age but the reverse was true
at 16 and 20 wk of age and the difference between lines
increase from 16 to 20 wk of age. At 16 wk of age, the
commercial sire lines have wider breasts than the F line
(Nestor et al., 2001a; present study).
Additive genetic variation, as indicated by differences
among lines, was an important source of variation for
BW at 16 and 20 wk of age, shank length, shank width
(females only), and breast width in the study of Nestor
et al. (2001a) and the present study. It has been shown
GENETIC VARIATION OF GROWTH TRAITS IN TURKEYS 1345
that large gains in BW (McCartney et al., 1968; Nestor,
1977, 1984; Nestor et al., 1996), breast width (Nestor et
al., 1969), and shank width (Nestor et al., 1985) can be
made by genetic selection within a line.
Nonadditive genetic variation was a significant source
of variation in BW of males at all ages in crosses of the
F line and commercial sire lines (Nestor et al., 2001a;
present study). For females, heterosis for BW at 8 wk of
age was significant in all crosses of the F and commercial
sire lines (Nestor et al., 2001a; present study) but the only
significant heterosis at older ages was for 16 wk BW in
the crosses of the B and F lines (Nestor et al., 2001a). Age
specific heterosis for BW has been previously reported
(Asmundson, 1942; Asmundson and Pun, 1954).
In earlier studies, nonadditive genetic variation in BW
weight was not an important source of variation (Kondra
and Shoffner, 1955; Clark, 1961; McCartney and Chamber-
lin, 1961; Nestor, 1971), except in some crosses in which
the parents differed greatly in body conformation (As-
mundson, 1945, 1948). More recent studies in which the
parental strains differed greatly in body conformation,
heterosis was an important source of variation (Emmer-
son et al., 1991; Ye et al., 1997; Nestor and Anderson,
1998; Nestor et al., 2001a). The F line differed from the
A, B, and C sire lines in breast width (Nestor et al., 2001a;
present study) and body shape (Nestor et al., 2001b; un-
published data). The differences in breast width and body
shape between the experimental F line and the commer-
cial sire lines might have been responsible for the hetero-
sis in BW observed. It is unknown why heterosis was
expressed to a greater extent in males than in females.
Inbreeding, as measured by band sharing of DNA fin-
gerprints (Kuhnlein et al., 1990; Zhu et al., 1996a), was
greater in the commercial sire lines than in the F line (Ye
et al., 1998). Accumulated inbreeding in the F line, as
calculated by variation in family size, was 30.1% (unpub-
lished data) when the crosses were made with sire line
C. Because the commercial sire lines and the F line are
moderately inbred, the heterosis observed in BW may
have been due to elimination of inbreeding effects by
crossing relatively unrelated lines. A linear relationship
is expected between the degree of heterosis and level of
inbreeding (Hill, 1982) and the magnitude of the heterosis
should be inversely related to the degree of genetic resem-
blance between parental populations (Wilhelm and Pol-
lak, 1985).
Nonadditive genetic variation in shank measurements
was not a consistent source of variation in the crosses of
the F line and commercial sire lines. No significant hetero-
sis was observed in the current study for any shank mea-
surements for crosses of the F and C line. In the study of
Nestor et al. (2001a), heterosis was a more important
source of variation for shank width and depth in males
than in females in crosses of the F and A and F and B lines.
No heterosis was observed in shank length for crosses of
A and F but significant, but small in magnitude, heterosis
was observed in crosses of B and F.
No heterosis in breast width was observed in crosses
of the F and commercial sire lines (Nestor et al., 2001a;
present study). Similarly, Asmundson (1948), Ye et al.
(1997), and Nestor and Anderson (1998) did not observe
heterosis in crosses of lines differing greatly in breast
width.
Heterosis in walking ability scores (7.54%) was sig-
nificant for females but not males. Nestor et al. (2001a) did
not observed any significant heterosis in walking ability
scores in crosses of the F and A lines but heterosis was
significant for males (12.9%) but not females in the
crosses of the F and B lines. Negative heterosis for walking
ability scores has been observed previously in reciprocal
crosses of the N and F lines (Emmerson et al., 1991) and
in a cross of an unimproved commercial sire line and the
FL line (Ye et al., 1997). When the FL line was reciprocally
crossed with the A and B lines, heterosis was negative
and significant for only males of 1 of the crosses (Nestor
and Anderson, 1998). The results of the present study and
those in the literature indicate that nonadditive genetic
variation in walking ability scores may be an important
source of variation in certain crosses.
Reciprocal effects, indicating sex linked or maternal
influences were not a consistent source of variation for
any trait. Maternal effects might have been expected be-
cause average egg weight different greatly in the F (95.4
g) and C (102.1 g) lines (unpublished data).
In summary, the F line had a different growth pattern
than the C line and heterosis was an important source of
variation in BW of males at 8, 16, and 20 wk of age. For
females, heterosis was significant in reciprocal crosses of
the F and C lines only at 8 wk of age. No significant
heterois was observed for breast width and width, depth,
or length of the shank. Significant negative heterosis in
walking ability scores was observed for females but not
males of the F and C crosses.
REFERENCES
Asmundson, V. S. 1942. Crossbreeding and heterosis in turkeys.
Poult. Sci. 21:311–316.
Asmundson, V. S. 1945. Inheritance of breast width in turkeys.
Poult. Sci. 24:150–154.
Asmundson, V. S. 1948. Inherited differences in weight and
conformation of bronze turkeys. Poult. Sci. 27:695–708.
Asmundson, V. S., and C. F. Pun. 1954. Inheritance of rate of
growth in bronze turkeys. Poult. Sci. 33:411–416.
Clark, T. B. 1961. Crossbreeding in turkeys. II. Summary of
studies on hatchability, growth and body characteristics.
West Virginia Agriculture Experiment Station Bulletin 455T.
Morgantown, WV.
Emmerson, D. A., N. B. Anthony, and K. E. Nestor. 1991. Genet-
ics of growth and reproduction in the turkey. 11. Evidence
of nonadditive genetic variation. Poult. Sci. 70:1084–1091.
Friars, G. W., F. N. Jerome, L. T. Weeden, and G. C. Ashton.
1963. Body weights and reproduction rates of two strains and
reciprocal crosses of Broad breasted Bonze turkeys. Poult. Sci.
42:935–940.
Havenstein, G. B., P. R. Ferket, J. L. Grimes, M. A. Qureshi, and
K. E. Nestor. 2004a. Performance of 1966 vs. 2003 turkeys
when fed representative 1966 and 2003 turkey diets. Proceed-
ings of the World’s Poultry Congress, Istanbul, Turkey.
Havenstein, G. B., P. R. Ferket, J. L. Grimes, M. A. Qureshi, and
K. E. Nestor. 2004b. Changes in the performance of turkeys–
1966–2003. Proceedings of the 17th Technical Turkeys Con-
ference, Macclesfield, Cheshire, UK.
NESTOR ET AL.1346
Hill, W. G. 1982. Dominance and epistasis as components of
heterosis. Z. Tier. Zuchtungbiol. 99:161–167.
Jerome, F. N., G. W. Friars, and L. T. Weeden. 1960. Heterosis
for growth in turkeys. Poult. Sci. 39:1225–1226.
Knox, C. W., and S. J. Marsden. 1944. The inheritance of some
quantitative characteristics in turkeys. J. Hered. 35:89–96.
Kondra, P. A., and R. N. Shoffner. 1955. Crossing strains and
breeds of turkeys. Poult. Sci. 34:1268–1274.
Kuhnlein, U., D. Zadworny, Y. Dawe, R. W. Fairfull, and J. S.
Gavora. 1990. Assessment of inbreeding by DNA finger-
printing: Development of a calibration curve using defined
strains of chickens. Genetics 125:161–165.
McCartney, M. G., and V. D. Chamberlin. 1961. Crossbreeding
turkeys. 2. Effect of mating system on body weight and con-
formation. Poult. Sci. 40:224–231.
McCartney, M. G., K. E. Nestor, and W. R. Harvey. 1968. Genet-
ics of growth and reproduction in the turkey. 2. Selection
for increased body weight and egg production. Poult. Sci.
47:717–721.
Naber, E. C., and S. P. Touchburn. 1970. Ohio poultry rations.
Ohio Cooperative Extension Service Bulletin 343. The Ohio
State University, Columbus, OH.
Nestor, K. E. 1971. Genetics of growth and reproduction in the
turkey. 4. Strain crossing for improvement of growth and
reproduction. Poult. Sci. 50:1683–1689.
Nestor, K. E. 1977. Genetics of growth and reproduction in the
turkey. 5. Selection for increased body weight alone and
in combination with increased egg production. Poult. Sci.
56:337–347.
Nestor, K. E. 1984. Genetics of growth and reproduction in the
turkey. 9. Long-term selection for increased 16-week body
weight. Poult. Sci. 63:2114–2122.
Nestor, K. E., and J. W. Anderson. 1998. Effect of crossing a line
selected for increased shank width and two commercial sire
lines on performance and walking ability. Poult. Sci.
77:1601–1607.
Nestor, K. E., J. W. Anderson, and R. A. Patterson. 2000. Genetics
of growth and reproduction in the turkey. 14. Changes in
genetic parameters over thirty generations of selection for
increased body weight. Poult. Sci. 79:445–452.
Nestor, K. E., J. W. Anderson, and S. G. Velleman. 2001a. Genetic
variation in pure lines and crosses of large-bodied turkey
lines. 1. Body weight, walking ability, and body measure-
ments of live birds. Poult. Sci. 80:1087–1092.
Nestor, K. E., J. W. Anderson, and S. G. Velleman. 2001b. Genetic
variation in pure lines and crosses of large-bodied turkey
lines. 2. Carcass traits and body shape. Poult. Sci. 80:1093–
1104.
Nestor, K. E., W. L. Bacon, Y. M. Saif, and P. A. Renner. 1985.
The influence of genetic increases in shank width on body
weight, walking ability, and reproduction in turkeys. Poult.
Sci. 64:2248–2255.
Nestor, K. E., M. G. McCartney, and N. Bachev. 1969. Relative
contribution of genetics and environment to turkey improve-
ment. Poult. Sci. 48:1944–1949.
Nestor, K. E., D. O. Noble, and D. A. Emmerson. 1997. Genetics
of growth and reproduction in the turkey. 13. Effects of re-
peated backcrossing of an egg line to two sire lines. Poult.
Sci. 76:227–235.
Nestor, K. E., D. O. Noble, J. Zhu, and Y. Moritsu. 1996. Direct
and correlated responses to long-term selection for increased
body weight and egg production in turkeys. Poult. Sci.
75:1180–1191.
SAS Institute. 1988. SAS/STAT User’s Guide. 6.03 ed. SAS Insti-
tute Inc., Cary, NC.
Wilhelm, R. L., and E. Pollak. 1985. Theory of heterosis. J. Dairy
Sci. 68:2411–2417.
Ye, X., J. W. Anderson, D. O. Noble, J. Zhu, and K. E. Nestor.
1997. Influence of crossing a line selected for increased shank
width and a commercial sire line on performance and walk-
ing ability of turkeys. Poult. Sci. 76:1327–1331.
Ye, X., J. Zhu, S. G. Velleman, and K. E. Nestor. 1998. Genetic
diversity of commercial turkey primary breeding lines as
estimated by DNA fingerprinting. Poult. Sci. 77:802–807.
Zhu, J., K. E. Nestor, and S. J. Lamont. 1995. Survey of major
histocompatibility complex haplotypes in four turkey lines
using restriction fragment length polymorphism analysis
with nonradioactive DNA detection. Poult. Sci. 74:1067–1073.
Zhu, J., K. E. Nestor, and Y. Moritsu. 1996a. Relationship be-
tween band sharing levels of DNA fingerprints and inbreed-
ing coefficients and estimation of true inbreeding in turkey
lines. Poult. Sci. 75:25–28.
Zhu, J., K. E. Nestor, and Y. Tang. 1996b. Frequencies and genetic
diversity of major histocompatibility complex class II haplo-
types in commercial turkey lines. Poult. Sci. 75:954–958.
... Apart from BWT trait, the Black genotype also exhibited the highest GCA in DSL, SL and KL followed by the white genotype while bronze genotype was the lowest. Elsewhere, Nestor et al (2005) reported a significant additive genetic effect for BrWt, SL, Walking ability and BWT at 8, 16 and 20 weeks of age in crosses of commercial turkeys. McCartney and Chamberlin (1961) concluded that additive genetic variance was much more important than non-additive genetic variance for BWT and body conformation in turkeys using diallel crosses. ...
... The absence of any significant RE indicates that there are no sexlinked or maternal effects exhibited by the various crosses. However Nestor et al (2005) reported a significant RE for SL in male and female turkeys in a reciprocal cross of a commercial sire line and a line selected for long term increased 16-week body weight. ...
... Although the non-additive genetic effect usually contributes only slightly to the sources of variation in growth (El-Gendy, 2009), significant variation due to heterosis was found in the present study during the entire study period for BW and BWG. In accord with these results, significantly different heterosis was reported for BW in turkey (Nestor et al., 2004(Nestor et al., , 2005, ducks (Padhi, 2010;Padhi and Sahoo, 2012), and broiler chicks (Rajkumar et al., 2011). In most crosses, the magnitude of heterosis estimates for growth traits had increased to week 8, but it tended to decrease afterward. ...
Preprint
Full-text available
The current experiment aimed to estimate crossbreeding parameters for body weight (BW), body weight gain (BWG), and feed conversion ratio (FCR) in genotypes generated through reciprocal mating between Fayoumi (FM) and three other exotic chicken breeds, namely, Koekoek (KK), Sasso (SS), and White Leghorn (WL) at different growth stages. Weights of individual birds were measured at hatch and 4, 8, 12, 16, and 20 weeks of age to determine BW and BWG. Feed intake for each genetic group was used to estimate feed conversion ratio (FCR). Results revealed that purebred effect (PE), general combining ability (GCA), maternal effect (ME), specific combining ability (SCA), and heterosis were highly significant in BW, BWG, and FCR at different ages. Purebred SS had the highest estimates of PE and GCA for BW and BWG but the lowest values for FCR, with KK having slightly similar values to that of SS. Closely followed by KK, purebred SS had the highest variation in ME for BW. Crosses of FM with WL and KK exhibited the highest SCA for BW and BWG and the lowest value for FCR, whereas reciprocal crosses between FM and KK had positive heterosis for BW and BWG but had negative heterosis for FCR. The results generally suggest the importance of additive and non-additive genetic variance for the inheritance of growth and feed efficiency traits. Therefore, a genetic improvement could be realized through selective breeding and crossbreeding strategies and/or a combination of the two. In crossbreeding programs involving these genotypes, specialized sire and dam lines as well as synthetic breeds having different combinations could be developed using genotypes showing the highest additive effects as males and those having the highest non-additive effects as female parents.
... These effects can explain the unique differences between male and female birds of the same genotype, where sexual dimorphism favored the former over the latter. In line with the present results, a significant interaction between the genetic group and sex was found in BW at 16 and 20 weeks in turkey (Nestor et al., 2005) and 12, 16, and 20 weeks in chicken (Momoh et al., 2010). A significant interaction between genotype and sex was also reported for BWG at 12-16 and 16-20 weeks (Momoh et al., 2010). ...
Preprint
Full-text available
The present study aimed to investigate the relative performance of crossbreds generated through reciprocal mating of Fayoumi (FM) with Koekoek (KK), Sasso (SS), and White Leghorn (WL), and the purebred parents for growth and feed efficiency traits. Birds were weighed individually at hatch and every four weeks to 20 weeks to determine body weight (BW) and body weight gain (BWG). Feed intake for each genetic group was used to estimate feed conversion ratio (FCR). Results revealed that significant differences (p < 0.001) existed among the genotypes in BW, BWG, and FCR. For these genotypes, SS outperformed all other genotypes throughout the study period. Reciprocal crosses of FM and SS performed better than the remaining seven genotypes, with KK and reciprocal crosses of KK and FM showing intermediate performance, while FM and WL and reciprocal crosses involving them performed least. Mating FM males with SS, KK, and WL produce crossbreds that outperformed their reciprocal crosses, suggesting that FM has a higher combining ability. Thus, females of these genotypes could be crossed with the third breed to generate crossbreds having higher feed efficiency and growth rates. The results also revealed that crossbreds had higher performance than FM and sometimes their other exotic parents. In most instances, reciprocal crosses of FM with KK and WL outperformed both of their parents in the growth and feed efficiency traits. Therefore, these genotypes could be used in any crossbreeding system to exploit the heterotic effects that existed in them, thereby improving the growth and feed efficiency traits.
... These implied that there were sex-linked or maternal effects exhibited by the various crosses for the traits BWT, HW and SC at the identified ages. Nestor et al. (2005) reported a significant RE for SL in male and female turkeys in a commercial sire line and a line selected for long term increased 16week body weight using orthogonal contrasts. However, Silva et al. (1996), using Griffing's (1956) method, estimated the maternal and reciprocal effects on bodyweight at birth, 21, 35, and 77 days in crosses involving Duroc, Landrace, Yorkshire and Large White and reported a significant maternal effect at birth, 21 days and 35 days of age and no significant reciprocal effect at these ages. ...
Article
Full-text available
Three breeds of pig namely; Indigenous (IN), Large white (LW) and Landrace (LR) breeds were crossed in full diallel arrangement to evaluate the effects of cross, sex and parity on growth traits as well as establish the nature of gene action due to the growth traits at birth, weaning and 20 weeks of age. Each line crossed in a full 3x3 diallel cross resulted in a total of 132, 107 and 105 pigs at birth, weaning and 20 weeks of age respectively. General Combining Ability (GCA), Specific Combining Ability (SCA) and Reciprocal Effects (RE) were estimated for eight traits which includes Body weight (BWT), Ear length (EL), Tail length (TL), Heart girth (HG), Snout circumference (SC), Snout length (SL), Height at wither (HW) and Body length (BL). There were significant differences (P < 0.05) among the various crosses, sex and parity but no significant interaction. The LRxLW cross consistently expressed higher body weight and morphometric traits than other crosses at birth, weaning and 20 weeks of age, while the INxIN expressed least body weight at birth and 20 weeks of age, while LWxIN was the least at weaning. There was no significant GCA effect (P>0.05) on all the traits measured, but SCA was significant (P<0.01) for all morphometric traits and body weight. RE was significant for body weight at birth and weaning, while at 20 weeks, was significant for SC and HW. The non-significant GCA estimates along with significant SCA estimates suggest that the genes governing the eight traits measured do not act additively, but non-additively, implying that improvement of those traits may be attained by exploiting heterosis through planned crossbreeding. However, the significant reciprocal effect in body weight and some morphometric traits indicates maternal and sex-linked effect at the affected ages, implying that significant reciprocal cross may be used to attain high performance for the growth traits in the progeny.
... These implied that there were sex-linked or maternal effects exhibited by the various crosses for the traits BWT, HW and SC at the identified ages. Nestor et al. (2005) reported a significant RE for SL in male and female turkeys in a commercial sire line and a line selected for long term increased 16week body weight using orthogonal contrasts. However, Silva et al. (1996), using Griffing's (1956) method, estimated the maternal and reciprocal effects on bodyweight at birth, 21, 35, and 77 days in crosses involving Duroc, Landrace, Yorkshire and Large White and reported a significant maternal effect at birth, 21 days and 35 days of age and no significant reciprocal effect at these ages. ...
Article
Three breeds of pig namely; Indigenous (IN), Large white (LW) and Landrace (LR) breeds were crossed in full diallel arrangement to evaluate the effects of cross, sex and parity on growth traits as well as establish the nature of gene action due to the growth traits at birth, weaning and 20 weeks of age. Each line crossed in a full 3x3 diallel cross resulted in a total of 132, 107 and 105 pigs at birth, weaning and 20 weeks of age respectively. General Combining Ability (GCA), Specific Combining Ability (SCA) and Reciprocal Effects (RE) were estimated for eight traits which includes Body weight (BWT), Ear length (EL), Tail length (TL), Heart girth (HG), Snout circumference (SC), Snout length (SL), Height at wither (HW) and Body length (BL). There were significant differences (P < 0.05) among the various crosses, sex and parity but no significant interaction. The LRxLW cross consistently expressed higher body weight and morphometric traits than other crosses at birth, weaning and 20 weeks of age, while the INxIN expressed least body weight at birth and 20 weeks of age, while LWxIN was the least at weaning. There was no significant GCA effect (P>0.05) on all the traits measured, but SCA was significant (P<0.01) for all morphometric traits and body weight. RE was significant for body weight at birth and weaning, while at 20 weeks, was significant for SC and HW. The non-significant GCA estimates along with significant SCA estimates suggest that the genes governing the eight traits measured do not act additively, but non-additively, implying that improvement of those traits may be attained by exploiting heterosis through planned crossbreeding. However, the significant reciprocal effect in body weight and some morphometric traits indicates maternal and sex-linked effect at the affected ages, implying that significant reciprocal cross may be used to attain high performance for the growth traits in the progeny.
... They state the ratio of measurements that characterize the proportionality of bird's body (Ivanov, et al., 1998, Donchev, et al., 1991. (Nestor, 2001(Nestor, /2005) studied the body shape, the growth and the various body measurements of several lines of turkeys. And (Lalev, 2001) published data about the regular growth rate in all body parts up to the age of 6 months, preserving equal proportions with exception of breast circumferences, in BUT 9 gobblers. ...
... Many factors affect live weight gain, carcass yield and meat quality in poultry (Nestor et al. 2005). Among those, season, feeding program, sex and diseases are the most relevant (Mazanowski, 1999;Mazanowski, 2000). ...
Article
Full-text available
Introduction: Many factors affect live weight gain and carcass yield in poultry. Among those, feeding program, sex and diseases are the most relevant. The aim of this study was to evaluate the effect of a high protein (HP) and a low protein (LP) feeding programs in male and female turkeys on liveweight, carcass yield and foot injuries. Method: The high protein (HP) program consisted in diets with a higher content of crude protein than those of the low protein (LP) program, although the metabolizable energy was similar in both programs. Liveweight gain, carcass yield and foot injuries were evaluated. A complete randomized design with factorial arrangement and 128 replicates per treatment were used. The statistical analysis included the effects of the feeding program, sex and the interaction. Results: The turkeys from the HP program were heavier (P<0.05) than those from the LP program at 15 and 19 weeks of age (10.0 vs 9.1 and 13.1 vs 11.9 kg, respectively). The male turkeys were heavier (P<0.05) than the females at those ages (10.6 vs 8.4; 14.7 vs 10.4 and 17.4 vs 11.8 kg, respectively). Carcass yield was also significantly greater (P<0.05) for males than for females at 19 and 23 weeks of age (78.8 % vs 77.6 % and 78.2 % vs 77.5 %, respectively). Foot injuries grade 2 (>1.5 cm of diameter) were more frequent (P<0.06) in the HP (28.3%) than in the LP (18.1%) program, and in males (P<0.05). Additionally, as turkeys got older, foot injuries grade 2 were more frequents (34.9, 37.8 y 60.2% for turkeys at weeks 15, 19 and 23 of age; P<0.05). Conclusion: The results indicated that turkeys raised in the HP program were heavier, and that males were heavier and yielded more carcass than females. Frequency and severity of foot injuries were highest in HP program, in males and in older turkeys.
... This could explain the non-additive genetic variations reported by Nestor et al. (2001). In a later report, Nestor et al. (2005) found that no significant source of genetic variation was present for BW, BrWt, or SL from 0 to 12 weeks. This is in line with the present findings which showed consistently higher maternal additive genetic effect than direct genetic effect. ...
... Estimates of reciprocal, maternal and sexlinked effects were computed using orthogonal contrasts according to Nestor et al., (2005) as shown in Table 1. The values in the body of this table are orthogonal contrast coefficients. ...
... This could explain the non-additive genetic variations reported by Nestor et al. (2001). In a later report, Nestor et al. (2005) found that no significant source of genetic variation was present for BW, BrWt, or SL from 0 to 12 weeks. This is in line with the present findings which showed consistently higher maternal additive genetic effect than direct genetic effect. ...
Article
Full-text available
Selection for increased 16-week body weight alone resulted in a large increase in body weight and a major reduction in egg production over nine generations of selection. The realized heritability estimates for 16-week body weight were .31 ± .04 and .30 ± .03, respectively, for males and females. The realized genetic correlation between female 16-week body weight and egg production was −.4 2 ± .12. Large negative realized genetic correlations (−.50 to −.63) were observed between female 16-week body weight and intensity of lay traits (average clutch length, maximum clutch length and rate of lay), while generally only small non-significant positive correlations were found between body weight and broodiness traits (number of broody periods, length of broody period, and total days lost from broodiness). No significant correlations with egg weight, percent fertility or hatchability of fertile eggs were observed. Gains in 16-week body weight of from approximately 1/4 to 1/2 of those observed when selecting for body weight alone were achieved in another line without any reduction in egg production by the use of a selection index which gave three times the emphasis on 16-week body weight as on 180-day egg production. The realized heritability of 16-week body weight and the realized genetic correlations with egg production, intensity of lay traits and broodiness traits were similar in this line to those estimated in the line selected only for increased 16-week body weight.
Article
Full-text available
RECENTLY there has been considerable interest among turkey breeders in the application of crossbreeding for the commercial production of turkeys. Since many outstanding pure strains of turkeys have been developed for growth and conformation, this seems a logical trend in order for the breeder to take advantage of any non-additive genetic effects that can be utilized only by crossing. Whether crossbreeding will be an economical mating system wherby heterosis can be utilized, depends to a large extent upon the availability of pure strains which will combine well for improvement in better growth, conformation and vigor of their progeny. Since relatively little is known concerning the effect of crossing present-day strains of turkeys on physical traits, a study was undertaken to compare the growth and conformation of progeny produced by purbred matings and several different systems of crossing in order to evaluate this method of mating for the commercial production of . . .
Article
Full-text available
IN RECENT years poultry breeding for commercial production has shown an increasing tendency to shift its emphasis from the development of improved pure strains to the selection of strains for use as crosses. This is due to the fact that the hybrid individual offers an opportunity to make use of overdominance and epistatic effects, which phenomena cannot be utilized fully in a pure strain. Furthermore, in a hybrid a larger number of loci are likely to show the effects of desirable dominant genes and less likely to show the expression of undesirable recessive ones than in a pure strain individual. Information on the mode of inheritance of various economic traits and the effects of crossing on such traits is essential in planning crossbreeding of turkeys. Asmundson (1942) crossed a number of turkeys differing in body size and type. He reports that all crossbreds exhibited heterosis in weight, but that it . . .
Article
Full-text available
IT HAS been shown that much of the difference in percentage rate of growth of large and small strains and varieties of chickens occurs during the earlier months of the birds’ post hatching life. Thus Asmundson and Lerner (1934) found that Barred Plymouth Rocks grew more rapidly than Single Comb White Leghorns up to 16 weeks of age but not thereafter. Inherited differences in percentage rate of growth have been demonstrated between breeds of chickens (Lerner and Asmundson, 1932) and within breeds and varieties (Asmundson and Lerner, 1933). Inherited differences in weight have been shown for chickens based on mature weights (Waters, 1931) and about 8 weeks of age (Schnetzler, 1936). The inheritance of differences in gain and in weight at 8 weeks in turkeys has been reported by Abplanalp and Kosin (1952). They, Knox and Marsden (1944) and Asmundson (1948) have reported inherited differences in the weight of 24-week-old . . .
Article
Full-text available
Asmundson (1942) reported on the offspring of a cross of Bourbon Red ♂ × Black ♀ ♀. The crossbreds resulting from this cross showed an acceleration in rate of growth over poults of both purebred parent breeds. This increase in rate of growth was considerable. At sixteen weeks of age the crossbred males weighed 4,508 gms. as compared to an average of 3,516 gms. for the pure Burbon and pure Black males. At the same age the crossbred females weighed 3,502 gms. while the average for females of the purebreds was 2,723 gms. However, crosses of the Black with a white variety and with Black-winged Bronze did not produce this heterotic effect. In a recent experiment, directed towards the production of a better turkey broiler, results which parallel those of Asmundson were obtained. Three strains of turkeys were involved in the matings. They were a Large White strain, a medium-weight . . .
Article
Full-text available
THE superiority of specific strain crosses of turkeys, with respect to measures of body weight, is gradually being established (Asmundson, 1942, 1948; Kondra and Shoffner, 1955; Jerome, Friars and Weeden, 1960; McCartney and Chamberlin, 1961a,b; and Clark, 1961). Only occasional crosses between strains of diverse body weight have tended to produce progeny larger than the heavier parental strains. The problem of reproduction in turkeys is apparent in the estimated percent hatchability of all turkey eggs set in the United States and Canada. Unweighted mean estimates for the period (1956 to 1960 inclusive) show that this statistic is in the general range of 55 percent as indicated by the data of Moats (1961) and Pettit (1961). That heritable variation for reproduction traits exists within populations of turkeys is evident in the reports of Wilson and Johnson (1946); Blow, Glazener, Dearstyne and Bostian (1951); Abplanalp and Kosin (1953) and Kondra and Shoffner . . .
Article
Full-text available
THERE are several methods which turkey breeders might use to improve reproductive efficiency of turkeys. Among these are (1) selection for increased egg production alone; (2) tandem selection for fast growth rate and high egg production; and (3) selecting one line for increased growth rate and another for increased egg production, then crossing males of the growth line with females of the egg line to obtain a desirable offspring. McCartney et al. (1968) and Nestor (1971) recently reported on the use of the first two methods above as a means of improving reproduction. Selection for increased egg production alone resulted in large increases in egg production the first few generations with little loss in body weight. In later generations, response to selection diminished and a major loss in body weight occurred. The loss in body weight was recovered by two generations of selection for increased 16-week body weight, but a…
Article
The theory of heterosis is expressed by simple genetic models. Relevant population means are deduced for differences in gene frequencies among populations. Heterosis for the one-locus, two-allele model is a function of the square of the difference in gene frequency multiplied by the dominance deviation. Heterosis, for a model with two loci and two alleles at each, contains an additive by additive epistatic term as well. Recombination loss in the F2 or the mating of similar crosses interse is a function of the recombination fraction between loci, differences in gene frequencies, and additive by additive and dominance by dominance epistatic effects.