´ M
. Lopez-Serrano et al. Livestock Production Science 64 2000 121 –131 125
of every cycle in the chosen sample as the chain al. 1983 found a significantly poorer overall leg
achieved a stationary trend, one value for every condition in Landrace than in Large White boars.
performance and exterior trait and a mean value from Other frequencies of culling due to lameness were
seven bivariate runs for STAY12 and STAY123 in 10.5 of all sows in Dutch herds, with an average
each line. The standard deviations of the mean productive lifespan of 2.9 parities Dijkhuizen et al.,
values of the samples were taken as standard errors 1989, and 12.6 and 10.2 for Landrace and
of the estimates, one for every trait, and the mean of crossbreds at early parities Sehested and Scherve,
seven estimations for both stayability traits in each 1996, respectively. Culling reasons were not com-
line. pletely recorded in our data.
4.2. Pattern of hazard curves
4. Results and discussion
The hazard curves from first litter to disposal are 4.1. Mean performance level for all traits
shown in Figs. 1 and 2. For both lines the instanta- neous risk of culling follows a characteristic pattern:
Means and standard deviations for the analysed the hazard rate increases with parity and age, that is,
traits are presented in Table 1. Daily gain is almost 3 the risk of a sow being removed during successive
g higher in Large White than in Landrace. However, 7-day periods. Equally spaced peaks of the curves
the measurements of backfat thickness are similar in are due to a repeated increase in the culling risk after
both lines, about 11 mm. The exterior scores for the weaning in each reproduction cycle because of health
different traits are slightly lower in Large White than and reproduction problems. There is a higher hazard
in Landrace sows, except for legs, which is scored rate in Large White than in Landrace sows until the
0.23 points higher in Large White. second litter, in agreement with mean stayabilities.
The proportion of culled sows from the first litter The evaluated stayability traits were chosen to
to the second was 20.1 1785 sows in Large White coincide with the first two peaks from first litter to
and 17.5 853 sows in Landrace. Disposal from third litter on the hazard rate curve of the productive
the first litter to the third was 37.5 3331 sows in life. The intervals between peaks represent the
Large White and 32.9 1608 sows in Landrace. farrowing intervals.
There is a slight difference in stayability between both lines in favour of Landrace. On the contrary,
4.3. Heritabilities Dagorn and Aumaitre 1979 found a higher culling
percentage in Landrace sows than in Large White Mean estimates of heritabilities and additive vari-
after the first three litters and reported that 8.8 of ances from all bivariate analyses between stayability
the sows were culled because of lameness. Webb et and the other traits are given in Table 2. Although
Table 1 ¯
Means x and standard deviations s of the traits in Large White and Landrace Traits
Large White Landrace
¯ ¯
n x
s n
x s
Daily gain g 21870
611.78 61.64
14944 608.67
59.81 Backfat thickness mm
21870 10.97
1.96 14944
11.00 1.98
Legs score 21865
4.39 0.86
14940 4.16
0.85 Length score
21861 5.34
0.70 14943
5.54 0.72
Muscle score 21864
5.25 0.87
14942 5.32
0.85 Height score
21861 5.20
0.79 14943
5.26 0.77
Type score 21865
5.07 0.87
14941 5.07
0.87 STAY12
8879 0.79
0.40 4881
0.82 0.37
STAY123 8879
0.62 0.48
4881 0.67
0.47
´ 126
M . Lopez-Serrano et al. Livestock Production Science 64 2000 121 –131
Fig. 1. Hazard curve of Large White sows after first litter to disposal.
Fig. 2. Hazard curve of Landrace sows after first litter to disposal.
Large White sows show a higher culling rate than other performance and exterior traits. Tholen and
Landrace in this study, it does not seem to influence Graser 1996 found slightly lower heritabilities for
the estimated heritabilities for stayability because the functional stayability from first to third litter 0.09
values are quite similar between both lines, 8 for and 0.07 in crossbreeds, and Krieter 1995 esti-
2
Large White and 7 for Landrace from first to mated a lower heritability of h 50.06. Moreover, the
second litter STAY12, and 10 for Large White heritabilities for stayability tend to increase with age
and 11 for Landrace from first to third litter or parity until the third litter STAY123. This
STAY123. These are lower in comparison to the phenomenon was explained by Hudson and Van
´ M
. Lopez-Serrano et al. Livestock Production Science 64 2000 121 –131 127
Table 2
heritabilities in both lines for backfat thickness were
Heritabilities and standard errors in brackets, and genetic
quite similar, 0.40 in Large White and 0.41 in
standard deviations of the traits
Landrace. Schulze et al. 1998, who used the same
Traits Large White
Landrace
defined backfat thickness trait in boars, found values
2 2
h s
h s
of 0.55 in Large White and 0.39 in Landrace, while
g g
Van Steenbergen 1990 calculated a heritability of
Daily gain 0.41 0.01
15.98 0.29 0.01
13.15
0.37.
Backfat thickness 0.40 0.01
0.95 0.41 0.02
1.04 Legs
0.13 0.01 0.28
0.13 0.01 0.28
Heritabilities of 13 were estimated for the non-
Length 0.14 0.01
0.20 0.15 0.02
0.22
linearly defined leg scores in this investigation in
Muscle 0.22 0.01
0.31 0.25 0.02
0.35
both lines. These values are in agreement with the
Height 0.18 0.01
0.24 0.18 0.02
0.24
values reported in the literature.
Type 0.15 0.01
0.26 0.12 0.02
0.24
The remaining exterior traits show moderately
STAY12 0.08 0.01
0.094 0.07 0.01
0.083 STAY123
0.10 0.01 0.118
0.11 0.01 0.126
higher heritabilities ranging from 0.12 in type to 0.25 in muscle. Despite the relatively subjective definition
of these traits by different judges, the estimates have Vleck 1981 in dairy cattle as a reduction in the
all 0.01 or 0.02 standard errors. Schulze et al. 1998 proportion of cows surviving to successive ages
also estimated heritabilities using a restricted max- because the variance of a binomial trait increases in
imum-likelihood method for the same traits in Large similar proportions in each category, i.e., if the
White and Landrace boars and found higher values proportion of animals surviving to an age decreases.
from 0.17 to 0.39, except for type 0.08 in Large Stayability in the populations of this investigation
White boars in comparison to 0.15 in sows in this decreased from 79 at STAY12 to 62 at STAY123
experiment. This is possibly due to the subjective in Large White sows, and from 82 at STAY12 to
definition of this trait. A lower heritability of 0.14 67 at STAY123 in Landrace sows Table 1. Even
was found Von Brevern, 1996 for a score for the though Hudson and Van Vleck 1981 considered
hams in five classes in crossbred sows, although the stayability as a vector or opportunity group measur-
first and last classes were not considered for analysis. ing the chance of a cow to survive to a certain age,
they included the record of a cow living at an earlier 4.4. Genetic correlations
opportunity group or time of herd life. The genetic standard deviations for STAY12 and STAY123 are
Performance is unfavourably genetically correlated 0.094 and 0.118, respectively, in Large White sows,
to both longevity traits Table 3. In particular, and is also high in Landrace, at 0.083 and 0.126,
significant unfavourable genetic correlations were respectively.
found between daily gain and stayability traits. There The performance traits showed expected heritabili-
is a difference between lines and the relationships ty values. The heritability for daily gain in every
become more unfavourable with later litters or bivariate estimation for both stayability traits in
increasing age, 20.28 and 20.32 in Large White, every line was calculated as mean value between the
and 20.06 and 20.12 in Landrace for STAY12 and two runs. The heritability value was higher for Large
STAY123, respectively. These results from pureb- White 0.41 than for Landrace 0.29. However,
reeds are in agreement with those of Tholen and Schulze et al. 1998 found the same heritability of
Graser 1996 in two crossbreeds, i.e., these were 0.41 in daily gain for Large White and Landrace
20.16 and 10.31 for STAY12, and 20.15 and boars. Von Brevern 1996 found a lower heritability
20.31 for STAY123. Although they calculated cor- 0.18 in crossbred sows. Other values of differently
relations with
uncorrected stayability
traits in
defined daily gain traits in boars ranged from the crossbreed sows, they were not corrected for re-
moderate values 0.23 in Swedish Landrace Johan- production performance.
nson, 1987 and 0.36 in Dutch herds Van Steen- Unfavourable genetic relationships were also
bergen, 1990 to 0.52 in French Large White and found between backfat thickness and stayability
Landrace Ducos
et al.,
1993. However,
Table 3. The correlations increased in Large White
´ 128
M . Lopez-Serrano et al. Livestock Production Science 64 2000 121 –131
Table 3 Genetic correlation of daily gain, backfat thickness and exterior with stayability standard errors in brackets
Traits Large White
Landrace STAY12
STAY123 STAY12
STAY123 Daily gain
20.28 0.09 20.32 0.09
20.06 0.08 20.12 0.09
Backfat thickness 0.22 0.09
0.27 0.08 0.24 0.08
0.11 0.09 Legs
0.08 0.09 0.002 0.08
0.19 0.08 0.36 0.08
Length 20.01 0.06
20.05 0.08 0.04 0.10
0.07 0.09 Muscle
20.01 0.08 20.07 0.09
20.06 0.09 20.11 0.10
Height 0.04 0.01
0.01 0.01 20.10 0.10
20.01 0.10 Type
20.07 0.08 20.05 0.08
20.12 0.10 0.02 0.09
from 0.22 to 0.27 for STAY12 and STAY123, Von Brevern 1996 also estimated an unfavourable
respectively. On the other hand the correlations genetic correlation r 50.33 in crossbred sows
g
decreased in Landrace from 0.24 to 0.11 for STAY12 between backfat thickness and a leg weakness trait
and STAY123, respectively. Tholen and Graser registered in three grades, which were measured at
1996 also found increasing values of 20.03 to selection day like in our study.
10.06 in a herd, and decreasing correlations from Favourable genetic relationships were found be-
0.36 to 0.22 in another herd, for the uncorrected tween the leg score trait and stayability in both lines,
stayability traits STAY12 and STAY123, respective- but they were more important in Landrace 0.19 with
ly. The explanation of these genetic correlations is STAY12 and 0.36 with STAY123 and were higher
based on a possible genetic antagonism between with increasing litter or age Table 3. In Large
backfat thickness measured at selection day and White sows correlations between leg score and
longevity after
farrowing. Difficulties
in sows
stayability were around zero. Results on stayability becoming pregnant due to a negative energy balance
traits in pig breeding are not available in the is a possible explanation for the unfavourable rela-
literature. The low correlation in Large White may tionship between backfat thickness and stayability,
be due to other reasons for disposal than leg weak- since reproduction problems are an important reason
ness, which have not been identified. For example for culling.
Rydhmer and Johansson 1998 reported the occur- The influence of backfat thickness on longevity
rence of disturbed milk production in Swedish could also be explained through leg weakness
Yorkshire, with an important genetic component
2
syndrome as a consequence of lower backfat thick- h 50.79 and unfavourably correlated to lean
ness. This has previously been described by other growth. But Van Steenbergen 1990 confirmed that
authors. Webb et al. 1983 found that Landrace some leg traits are correlated with longevity, which
boars with lower fat levels developed leg weakness were relevant in relation to disposal for leg weak-
earlier in life. Bereskin 1979 also reported that pigs ness. He also found favourable genetic correlations
with better legs were fatter, and Lundeheim 1987 like in this study, between other leg traits, recorded
estimated an unfavourable genetic correlation of as gait and swinging of back with lifetime expecta-
20.43 between lean percentage and leg weakness tion r 50.46 and r 5 20.51, respectively. Un-
g g
score in Landrace. In this respect, Rothschild and favourable leg status or gait, because of selection for
Christian 1988b showed that selection for leaner performance Grøndalen, 1974b; Webb et al., 1983;
pigs, like the sows in the present study, leads to the Lundeheim, 1987, leads to involuntary culling.
loss of adequate front-leg structure in Duroc swine. Therefore, from our results it can be said that better
It is in agreement with the unfavourable genetic leg status is positively related with stayability or
correlations between backfat thickness and the ex- longevity in Landrace. The disease osteochondrosis
terior traits of gait and swinging of back r 50.26 dissecans explains, in part, the genetic background of
g
and r 5 20.11, respectively, that are associated the leg weakness syndrome Schilling, 1963; Lun-
g
with longevity according to Van Steenbergen 1990. deheim, 1987; Nakano et al., 1987, Stern et al.,
´ M
. Lopez-Serrano et al. Livestock Production Science 64 2000 121 –131 129
1995, and thereby, also longevity. In this respect, a traits could be an indirect reason for culling as a
QTL for osteochondrosis was found Andersson- manifestation of unfavourable condition or con-
Eklund et al., 1998, which could be taken as a QTL formation expressed through leg weakness, but the
for survival. results of this study only show the importance of leg
The remainder of the scored exterior traits, length traits as a measurement of involuntary culling in
of the sow, muscle, height and type, gave unim- Landrace.
portant and inconsistent genetic correlations with stayability in both lines Table 3. The subjective
judgment of these traits collected by different judges
5. Conclusions
