268 P
. Sellier et al. Livestock Production Science 63 2000 265 –274
calculated from the weighted selection differentials achieved for each of the index traits, the weighting
factor being the number of sons recorded per sire. Direct and correlated responses to selection for
male traits, ADG and BFAT were estimated by using the procedure GLM of SAS 1989. The model
included the fixed effects of line, generation year and line3generation interaction, as well as the fixed
effects of sex and sex3line interaction for ADG and BFAT, and a covariate as appropriate weight on test
for ADG and weight at measurement for BFAT and male traits. Data on the proportion of puberal gilts at
116.8 kg BW and the categorical GPUBS variable were analyzed according to Grizzle et al. 1969.
Analysis was based on logits using the maximum likelihood method available in the procedure CAT-
MOD of SAS 1989.
Variance-covariance components were estimated by using a restricted maximum likelihood REML
procedure applied to a multivariate individual animal model. The model varied depending on the trait as
mentioned above, but the basic mixed model in-
Fig. 1. Line differences select–control across generations in the
cluded the fixed effect of generation year and the
two component traits of the selection index: a fat androstenone
random effects of litter of birth and additive genetic
level at 117.6 kg BW LAND2; b bulbo-urethral gland thick- ness at 99.1 kg BW TBUG1. Vertical bar5difference6SE;
value of the animal. Suitable Box–Cox power trans-
5P ,0.001.
formations were performed for fat AND data BCAND1 and BCAND2 using the following for-
p
mula MacLean et al., 1976: y 5 r p[x r 1 1 2 1] where y and x are transformed and raw values,
and TBUG1. There was no significant change across respectively, r 5 10 and p 5 2 19.3.
generations in the difference between select and A series of three- or four-trait analyses were
control lines in fat AND level at 117.6 kg BW. In performed using the version 4.2 of the
VCE
software contrast, a significant increase in the difference
package Neumaier and Groeneveld, 1998. All
VCE
between select and control lines in average BUG runs comprised the traits TBUG1 and BCAND2 in
thickness at 99.1 kg BW occurred, mainly from the order to account for the effects of the selection being
third generation of selection. The pattern of direct achieved on these traits see Hofer, 1998 There
responses to selection clearly differed from that were 1935 animals in the pedigree file going back to
intended when defining the breeding goal, i.e. reduc- the parents of the foundation population. Approxi-
ing LAND2 while holding TBUG1 constant. One of mate standard errors of estimated genetic parameters
the reasons contributing to this unexpected result lies were obtained from an approximation of the Hessian
in that the ‘index-in-retrospect’ actually applied in matrix when convergence was reached.
each generation except the first one gave a higher weighting to TBUG1 than intended, as shown in
Table 2. Over the four generations of selection, the
3. Results average realized relative weight of TBUG1 com-
pared to LAND2 when expressing the traits in SD 3.1. Direct and correlated responses to selection
units was 1.12 instead of the intended value of 0.76. Correlated responses in LAND1 and WBUG2
The trends displayed by the select line compared Table 3 were in general agreement with those
to the control line are presented in Fig. 1 for LAND2 found for LAND2 and TBUG1, respectively. No
P . Sellier et al. Livestock Production Science 63 2000 265 –274
269 Table 2
Table 4 Coefficients of the ‘indexes in retrospect’ in generations G –G
Line differences across generations in percentage of gilts having
1 4
a
traits expressed in phenotypic SD units attained puberty prior to 116.8 kg BW
Generation w TBUG1
w LAND2 RRW1
Generation Control
Select Significance of the
1 2
line line
line difference G
1.59 22.63
0.60
1
G 2.03
21.68 1.21
G 15.8
24.1 –
2 1
G 1.90
21.20 1.58
G 8.9
33.3
3 2
G 1.71
21.61 1.06
G 15.8
40.7
4 3
G 23.2
40.4 –
a 4
RRW1 is the realized relative weighting for TBUG1 absolute value of the ratio of w to w . The relative weighting for TBUG1
5P ,0.01.
1 2
in the ‘intended’ selection index was 0.76.
2
response to selection was observed for fat AND level in Table 5 for heritabilities h and common litter
2
at 99.1 kg BW LAND1. A significant positive trend environment effects c , and in Table 6 for pheno-
occurred in line S for BUG weight at 122.7 kg BW typic r and genetic r correlations.
P A
WBUG2, and was similar to that displayed by The traits BCAND2 and TBUG1 showed similar
BUG size at 99.1 kg BW TBUG1. Weight of testes heritabilities, a positive phenotypic correlation, and a
2
at 122.7 kg BW WTES2 was consistently greater in close genetic correlation of 0.6660.06. The h
the select than in the control line through the estimate for BCAND1 did not differ from that for
generations G –G , but the line difference was BCAND2, and the two traits were closely correlated
1 4
significant only at generation G . both at the phenotypic and genetic levels. Similarly,
3
The overall proportion of gilts having shown first oestrus prior to 116.8 kg BW was 0.25 in this
Table 5
2
experiment. The proportion of puberal gilts was
Estimates of heritabilities h and common litter environment
2
higher whatever the generation in line S compared to
effects c for fat androstenone levels BCAND1, BCAND2, male genital tract measurements TBUG1, LBUG2, WBUG2,
line C 0.35 vs. 0.16, on average, and the line
WTES2, gilt puberty status GPUBS, average daily gain ADG
difference in this trait was significant at generations
and backfat thickness BFAT
G and G Table 4. Regarding the ovulation rate at
2 3
2 2
Trait No. of records
h 6SE c 6SE
the pubertal oestrus, line S 14.260.3, n 5 79 did
a
not significantly differ from line C 14.760.4, n 5
BCAND1 845
0.4960.06 0.0860.02
BCAND2 949
0.5560.05 0.0260.01
36 whatever the generation.
TBUG1 999
0.6360.06 0.0460.02
There were no significant correlated responses to
a
LBUG2 746
0.3360.04 0.1260.01
selection in ADG and BFAT results not shown.
a
WBUG2 746
0.5560.04 0.0460.01
a
WTES2 743
0.6160.04 0.0460.01
3.2. Estimated genetic parameters
GPUBS 455
0.5360.10 0.0760.06
ADG 1454
0.3460.04 0.1760.03
a
BFAT 1305
0.5760.03 0.1060.02
The REML-estimated parameters pertaining to
a
Traits not recorded on G boars.
nine traits recorded in this experiment are presented
Table 3
a
Line differences select–control across generations in fat androstenone level at 99.1 kg BW LAND1 and male genital tract measurements at 122.7 kg BW LBUG2, WBUG2, WTES2
Generation LAND1
LBUG2 WBUG2
WTES2 G
20.4460.15 0.3460.16
20.2060.16 0.1760.16
1
G 20.2060.15
0.2560.16 0.0760.16
0.2860.16
2
G 0.2360.16
0.4860.17 0.6660.17
0.4760.17
3
G 20.1560.14
0.1360.14 0.4260.14
0.2260.14
4 a
Differences expressed in SD units of the trait. 5P ,0.05, 5P ,0.01, 5P ,0.001.
270 P
. Sellier et al. Livestock Production Science 63 2000 265 –274 Table 6
a
Estimates of phenotypic and genetic correlations among fat androstenone levels BCAND1, BCAND2, male genital tract measurements TBUG1, LBUG2, WBUG2, WTES2, gilt puberty status GPUBS, average daily gain ADG and backfat thickness BFAT
Trait BCAND1
BCAND2 TBUG1
LBUG2 WBUG2
WTES2 GPUBS
ADG BFAT
BCAND1 –
0.97 0.65
0.34 0.58
0.47 0.22
0.04 0.11
0.02 0.06
0.08 0.06
0.08 0.09
0.14 0.12
BCAND2 0.71
– 0.66
0.54 0.68
0.41 –0.08
–0.16 0.11
0.06 0.10
0.07 0.08
0.13 0.12
0.09 TBUG1
0.37 0.38
– 0.83
0.93 0.54
0.41 –0.30
–0.07 0.07
0.03 0.07
0.12 0.09
0.08 LBUG2
0.30 0.42
0.60 –
0.90 0.26
0.12 –0.30
–0.23 0.03
0.11 0.17
0.11 0.15
WBUG2 0.35
0.51 0.80
0.84 –
0.46 0.34
–0.33 –0.14
0.07 0.15
0.13 0.13
WTES2 0.18
0.22 0.26
0.32 0.37
– 0.45
–0.29 –0.34
0.10 0.09
0.11 GPUBS
– –
– –
– –
– –0.58
0.02 0.10
0.09 ADG
0.13 20.06
20.16 20.15
20.22 20.13
20.16 –
–0.16 0.12
BFAT 0.12
0.18 20.19
20.10 20.13
20.12 0.04
0.29 –
a
Phenotypic correlations below the diagonal, genetic correlations SE between brackets above the diagonal.
2
the h estimates for WBUG2 and TBUG1 were of ment comprised a control line, a line selected for low
the same order and the two traits were highly fat AND level and small testis size ‘agonistic’
correlated. Heritability of testes weight WTES2 selection, and a line selected for low fat AND level
was similar to that of WBUG2, whereas the genetic and large testis size ‘antagonistic’ selection. The
association of WTES2 with BUG size measurements responses found in the latter line, i.e. a significant
was of medium magnitude. The genetic correlation decline of fat AND level and no genetic change in
of fat AND level BCAND1 or BCAND2 with weights of testes and bulbo-urethral glands, sug-
BUG size TBUG1 or WBUG2 was of the same gested that it would be feasible by breeding to reduce
order whatever the respective stages of measurement fat AND level without adversely affecting sexual
2
of the two traits. The h estimate for gilt puberty
maturity status in boars. The study reported here was status GPUBS was about 0.50, and this trait
designed for confirming this finding over a greater showed positive genetic correlations with TBUG1,
number of generations of selection while replacing WBUG2 and WTES2. There was a significant nega-
testis size by the development of accessory sex tive genetic relationship between GPUBS and ADG.
glands BUG for appraising the stage of sexual The phenotypic and genetic correlations of fat AND
maturation attained by young boars at a fixed body levels with ADG and BFAT were of small mag-
weight. nitude. The two latter traits showed moderate nega-
tive genetic correlations with male genital tract 4.1. Responses to selection
measurements. 4.1.1. Direct responses
Using a restricted selection index has resulted in
4. Discussion realized genetic trends for each component trait
