L . Wallin et al. Livestock Production Science 63 2000 275 –289
279
The survival of warmblood and coldblood horses Table 2. The probabilities of death for the males
in the CHF data was studied using model 4 without were higher for almost all ages compared with the
any explanatory variable, but analysed separately for mares. A slightly higher probability of death was
each sex. The dependent variable was length of life, noted for the age group 11 years than for other ages
defined as year of death or censoring, minus year of of the mares. Thus, the tendency was that mares
birth. The same procedure was applied to the stud lived longer than males. The mares had a 14-years
book data of brood-mares. survival rate of 72 compared with 51 for the
Frequencies of diseases leading to death were males.
2
tested for sex differences by x -analysis using SAS,
Among the CHF warmblood geldings few died 1989.
before the age of 7, Table 3. Higher probabilities of death were seen in the age groups 7 to 9 years for
geldings. The 14-years survival rate was 53. It was
4. Results difficult to interpret the figures on numbers of dead
mares because there were so few mares in the study. 4.1. Probability of death
No geldings among the coldblood horses had died at the age of 3 and 4 years, and no mares before the
The number of dead horses in the RHQT data age of 6, Table 4. Few mares had died before the age
study was 503 and the distribution between sexes of 9. The probability of death was rather low before
showed more dead males than mares 339 164, the age of 11 for both sexes. At the age of 14
Table 2 Lifetable for horses in the Riding Horse Quality Test data, distributed by age and sex
Year Males
Mares x
No. at With-
Deaths Prob.
Cumulative No. at
With- Deaths
Prob. of Cumulative
start drawn
d of death
prob. of start
drawn d
death prob. of
x x
b b
n during
q surviving x
n during
q surviving x
x x
x x
year years
year years
a c
a c
W P
W P
x x
x x
4 983
6 0.0061
0.9939 864
0.0000 1.0000
5 977
34 0.0348
0.9593 864
24 0.0278
0.9722 6
943 51
0.0541 0.9074
840 22
0.0262 0.9468
7 892
48 0.0538
0.8586 818
14 0.0171
0.9306 8
844 134
52 0.0669
0.8011 804
121 17
0.0229 0.9093
9 658
106 41
0.0678 0.7468
666 117
21 0.0346
0.8778 10
511 103
34 0.0740
0.6916 528
111 16
0.0339 0.8481
11 374
81 27
0.0810 0.6356
401 118
19 0.0556
0.8010 12
266 86
14 0.0628
0.5957 264
66 5
0.0216 0.7837
13 166
33 10
0.0669 0.5558
193 46
6 0.0353
0.7560 14
123 31
8 0.0744
0.5145 141
59 6
0.0538 0.7153
15 84
13 4
0.0516 0.4879
76 11
5 0.0709
0.6646 16
67 25
5 0.0917
0.4432 60
18 2
0.0392 0.6385
17 37
17 5
0.1754 0.3654
40 13
3 0.0896
0.5813 18
15 2
0.0000 0.3654
24 5
1 0.0465
0.5543 19
13 6
0.0000 0.3654
18 7
0.0000 0.5543
20 7
5 0.0000
0.3654 11
5 3
0.3529 0.3587
21 2
1 0.0000
0.3654 3
3 0.0000
0.3587 22
1 1
0.0000 0.3654
n5 983
339 864
164
a
W 5 n 2 n 2 d .
x x
x 11 x
b
q 5 d r r number at risk5n 2 0.5 w .
x x
x ; x
x x
c
P 5 p P p prob. of surviving year x 51 2 q .
x x
x 21; x
x
280 L
. Wallin et al. Livestock Production Science 63 2000 275 –289 Table 3
Lifetable for warmblood geldings of the Cavalry Horse Foundation, distributed by age Year
Number With-
Deaths Prob.
Cumulative x
at start drawn
d of death
prob. of
x b
n during
q surviving x
x x
year years
a c
W P
x x
3 306
1 0.0033
0.9967 4
305 3
0.0098 0.9869
5 302
7 0.0232
0.9641 6
295 5
0.0169 0.9477
7 290
22 0.0759
0.8758 8
268 14
0.0522 0.8301
9 254
19 0.0748
0.7680 10
235 9
0.0383 0.7386
11 226
15 0.0664
0.6895 12
211 15
0.0711 0.6405
13 196
17 0.0867
0.5850 14
179 22
16 0.0952
0.5293 15
141 27
18 0.1412
0.4545 16
96 26
9 0.1084
0.4053 17
61 23
8 0.1616
0.3398 18
30 15
2 0.0889
0.3096 19
13 8
5 0.5556
0.1376 n 5
306 185
a
W 5 n 2 n 2 d .
x x
x 11 x
b
q 5 d r r number at risk5n 2 0.5 w .
x x
x ; x
x x
c
P 5 p P p prob. of surviving year x 51 2 q .
x x
x 21; x
x
geldings had a survival rate of 69 and the mares group was introduced as an explanatory variable in
62. the model. The estimated median length of life for
Table 5 shows that rather few warmblood brood- both sexes born in the second and third birth-year
mares died before the age of 10 years, although a groups 1976–1979 and 1980–1982, respectively
slightly higher probability of death was seen at the were significantly longer P ,0.05 than for those
age of 7. The number of dead mares increased from born in the first group 1968–1975.
the age of 11, with a critical age at 16 where the For warmblood brood-mares and mares that par-
probability of death was rather high. ticipated in the RHQT and born between 1968 and
1975, comparable figures of 18.6 and 18.3 years 4.2. Length of life
were found. Close agreement was also found be- tween geldings of the CHF and males that had
The results from the survival analyses of all three participated in the RHQT and that were born be-
datasets are reported in Table 6. The median length tween 1968 and 1975; the estimates were 14.7 and
of life is given for each group of horses, by sex. 13.9 years, respectively.
Average standard errors are given from the replicated There was a significant difference P ,0.05 in
analyses conducted. length of life between coldblood geldings and mares
The median length of life for all mares that from the CHF. The difference in length of life
participated in the RHQT regardless of birth of year between warmblood geldings and coldblood geldings
was 22.2 years SE51.2, a statistically significant from the CHF was highly significant P ,0.001. A
difference of 7.5 years compared with the males. small difference P ,0.05 was found between mares
There was a positive trend in the median length of that participated in the RHQT and born between
life over time. This was shown when birth-year 1968 and 1975 and coldblood mares.
L . Wallin et al. Livestock Production Science 63 2000 275 –289
281 Table 4
Lifetable for coldblood horses of the Cavalry Horse Foundation, distributed by age and sex Year
Geldings Mares
x No. at
With- Deaths
Prob. Cumulative
No. at With-
Deaths Prob. of
Cumulative start
drawn d
of death prob. of
start drawn
d death
prob. of
x x
b b
n during
q surviving x
n during
q surviving x
x x
x x
year years
year years
a c
a c
W P
W P
x x
x x
3 115
0.0000 1.0000
89 0.0000
1.0000 4
115 0.0000
1.0000 89
0.0000 1.0000
5 115
3 0.0261
0.9739 89
0.0000 1.0000
6 112
1 0.0089
0.9652 89
1 0.0112
0.9888 7
111 4
0.0360 0.9304
88 1
0.0114 0.9775
8 107
4 0.0374
0.8957 87
1 0.0115
0.9663 9
103 3
0.0291 0.8696
86 2
0.0233 0.9438
10 100
2 0.0200
0.8522 84
3 0.0357
0.9101 11
98 6
0.0612 0.8000
81 5
0.0617 0.8539
12 92
3 0.0326
0.7739 76
4 0.0526
0.8090 13
89 5
0.0562 0.7304
72 7
0.0972 0.7303
14 84
10 4
0.0506 0.6935
65 14
9 0.1552
0.6170 15
70 9
7 0.1069
0.6193 42
11 3
0.0822 0.5663
16 54
14 4
0.0851 0.5666
28 6
3 0.1200
0.4983 17
36 7
3 0.0923
0.5143 19
7 0.0000
0.4983 18
26 13
2 0.1026
0.4616 12
6 1
0.1111 0.4430
19 11
8 3
0.4286 0.2638
5 2
3 0.7500
0.1107 n 5
115 54
89 43
a
W 5 n 2 n 2 d .
x x
x 11 x
b
q 5 d r r number at risk5n 2 0.5 w .
x x
x ; x
x x
c
P 5 p P p prob. of surviving year x 51 2 q .
x x
x 21; x
x
Accumulated percentages of dead horses for the comprised about the same proportion 9 of the
three birth-year groups in the RHQT data are shown dead horses.
in Fig. 2. Horses in the three groups were able to Table 8 shows different diseases within the pre-
reach the age of 15, 11 and 8 years, respectively. The dominant group, the musculoskeletal system. Dis-
curves show a positive trend in accumulated per- eases of the joints were associated with 45 of all
centages of dead horses for the three age groups. deaths in this group and degenerative joint disease
According to the curves, horses born between 1980 was the most frequent within that. Fewer than 6 of
and 1982 had a longer expected lifespan than had the the horses in this group were diagnosed as having
other two groups. osteochondrosis. As regards other skeleton problems,
fractures predominated, but navicular disease also constituted a rather large group. Almost 14 of the
4.3. Causes of culling and death horses were culled due to lameness, but more
specific causes of the problems were not given. 4.3.1. Swedish Riding Horse Quality Test data
Diseases of the back, including the sacroiliac joint, Table 7 shows that diseases of the musculoskeletal
and of tendons constituted together 13 of all deaths system were the predominant cause of death, ac-
from diseases of the musculoskeletal system. counting for about 55 of the dead warmblood
In the accident category, horses on pasture had the horses. This was the major cause of death in both
highest frequency 30. However, in nearly as sexes, although there was a highly significant differ-
many of the cases, the accident was not defined. ence among them. Accidents and diseases of the
Road traffic accidents and fire were the causes of respiratory system were much less common and
death of about 2 and 1, respectively, in all cases.
282 L
. Wallin et al. Livestock Production Science 63 2000 275 –289 Table 5
Lifetable for warmblood stud book brood-mares Year
No. With-
Deaths Prob.
Cumulative x
at start drawn
d of death
prob. of
x b
n during
q surviving x
x x
year years
a c
W P
x x
4 481
1 0.0021
0.9979 5
480 2
1 0.0021
0.9958 6
477 3
3 0.0063
0.9896 7
471 6
19 0.0406
0.9494 8
446 2
4 0.0090
0.9408 9
440 1
8 0.0182
0.9237 10
431 6
4 0.0093
0.9151 11
421 3
13 0.0310
0.8867 12
405 10
17 0.0425
0.8490 13
378 17
22 0.0595
0.7985 14
339 16
25 0.0755
0.7382 15
298 8
21 0.0714
0.6855 16
269 11
37 0.1404
0.5892 17
221 17
25 0.1176
0.5199 18
179 25
23 0.1381
0.4481 19
131 20
1 0.0826
0.4110 20
101 4
9 0.0909
0.3737 21
88 11
10 0.1212
0.3284 22
67 9
8 0.1280
0.2863 23
50 18
3 0.0732
0.2654 24
29 19
2 0.1026
0.2382 25
8 6
1 0.2000
0.1905 26
1 1
0.0000 0.1905
n 5 481
266
a
W 5 n 2 n 2 d .
x x
x 11 x
b
q 5 d r r number at risk5n 2 0.5 w .
x x
x ; x
x x
c
P 5 p P p prob. of surviving year x 51 2 q .
x x
x 21; x
x
Table 6 Estimated median length of life years and standard errors SE according to survival analyses of the different horse populations
Horse category Birth year
Males Mares
Difference mares–males
Number Length
Number Length
of life of life
a
Riding horse quality 1968–1975
176 13.960.8
116 18.361.4
4.4
a
Tested warmblood 1976–1979
370 15.360.8
366 22.061.9
6.7
a
horses 1980–1982
437 16.061.1
382 26.563.8
10.5
a
Total 1968–1982
983 14.760.5
864 22.261.2
7.5 Cavalry horses
Warmblood 1970–1975
306 14.760.4
b
Coldblood 1970–1975
115 17.660.8
89 16.460.6
21.2 Warmblood stud
1965–1967 481
18.660.4 book mares
a
Significance tests between mares and males: P ,0.001.
b
Significance tests between mares and males: P ,0.05.
L . Wallin et al. Livestock Production Science 63 2000 275 –289
283 Table 8
Numbers of deaths attributed to diseases of the musculoskeletal system among horses in the Riding Horse Quality Test data
a
Site of disease injury Number
Percentage Joints
125 44.8
Degenerative joint disease 101
36.2 Osteochondrosis
16 5.7
Miscellaneous 6
2.2 Upward patella fixation
2 0.7
Skeleton 80
28.7 Fractures
46 16.5
Navicular disease 34
12.2 Diseases of the back
21 7.5
including the sacroiliac joint Vertebrae joints
11 3.9
Undefined 7
2.5 Fig. 2. Accumulated percentages of dead horses of both sexes in
Myopathies 3
1.1 the Riding Horse Quality Test, distributed by birth-year group;
b
Tendons 15
5.4 1968–1975 -j-, 1976–1979 -m-, 1980–1982 -d-.
Undefined lameness 38
13.6 Total
279 100.0
Almost all horses 42 of 45 included in the
a
Percent of horses whose death was attributable due to diseases
category diseases of the respiratory system had been
of the musculoskeletal system.
culled because of chronic obstructive pulmonary
b
The cause was tendinitis in all cases.
disease. Diseases of the digestive system were dominated by gastrointestinal displacement 22 of
28. wobbler syndrome and temperamental disorders 10
Diseases of the nervous system constituted a and 5 of 27, respectively.
significantly greater problem for geldings than for Of the horses put down because of hoof problems
mares, the main causes being as different as the 12 of 23 were culled because of laminitis. Other
Table 7 Causes of death of horses in the Riding Horse Quality Test data, distributed by sex
Cause of death Number
Percentage Total
Males Mares
Total Males
Mares
a
Musculoskeletal system 279
204 75
55.5 60.1
45.7 Accidents
46 27
19 9.1
8.0 11.6
Respiratory system 45
29 16
8.9 8.6
9.8 Digestive system
28 16
12 5.6
4.7 7.3
b
Nervous system 27
21 6
5.4 6.2
3.6 Hoof
23 15
8 4.6
4.4 4.9
Circulatory system 13
5 8
2.6 1.5
4.9 Tumours
7 7
1.4 2.1
0.0 Reproductive tract
7 7
1.4 0.0
4.3 Urinary system
2 2
0.4 0.6
0.0 Infectious diseases
1 1
0.2 0.3
0.0 Miscellaneous
4 4
0.8 0.0
2.4 Unknown
21 12
9 4.2
3.5 5.5
Total 503
339 164
100.0 100.0
100.0
a
Significance tests between sexes: P ,0.001.
b
Significance tests between sexes: P ,0.05.
284 L
. Wallin et al. Livestock Production Science 63 2000 275 –289
causes were ossification of collateral cartilages of the were navicular disease and fractures. Chronic ob-
distal phalanx sidebones 5 and pedal osteitis 3. structive pulmonary disease was the cause of culling
Among diseases of the circulatory system, 9 of 13 of all horses in the second largest group Table 9.
horses died of cardiac disorders acute chronic. Diseases of the digestive system were dominated by
The proportions of dead horses in the three most colic of an undefined nature seven of ten. As
frequent groups of diseases causing death, distributed regards hoof diseases, most horses were culled
according to age, are shown in Fig. 3. Musculoskele- because of laminitis four of seven. Causes of death
tal problems constituted a relatively more common due to diseases of the nervous system were divided
cause of death in the age range 7 to 10 years than at between
temperamental disorders
and wobbler
younger and older ages. Young horses were more syndrome three and two of six, respectively.
often the victim of accidents than of diseases of the Lymphangitis caused the death of four of five horses
respiratory system. The latter category showed an among those with diseases of the circulatory system.
increasing incidence with age. The figures at the ages Unfortunately, 14 of the dead horses did not have
of 4 years and 12–14 years are, however, based on any documented cause of death.
small numbers of horses and must be interpreted Among the coldblood horses, temperamental dis-
with caution. orders were the most common cause of culling 20
of 22. Diseases of the musculoskeletal system 4.3.2. Swedish Cavalry Horse Foundation data
constituted a large group too, undefined lameness Diseases of the musculoskeletal system were the
being the most frequent cause of culling. The third cause of most deaths among warmblood horses, and
group concerned hoof diseases, where sidebones and the primary cause of culling for both sexes, Table 9.
laminitis were the cause of culling for four and three Table 10 shows that 55 of the dead horses had
horses of eight, respectively. The number of un- joint diseases, practically all being degenerative joint
known causes of death among the coldblood horses disease. The dominant causes of skeletal problems
was rather high 26.
Fig. 3. Relative percentage distribution of major causes of death in different age groups for horses in the Riding Horse Quality Test: diseases of the musculoskeletal system -♦-, diseases of the respiratory system -m- and accidents -d-. Total numbers of dead horses in
each age group given in parentheses.
L . Wallin et al. Livestock Production Science 63 2000 275 –289
285 Table 9
Causes of death among warmblood and coldblood horses in the Cavalry Horse Foundation data for geldings G and mares M Cause of death
Warmblood Coldblood
Total number Number
Total number Number
n G
M n
G M
Musculoskeletal system 119
57.2 107
12 13
13.4 6
7 Respiratory system
17 8.2
15 2
2 2.1
2 Digestive system
10 4.8
9 1
6 6.2
4 2
Hoof 7
3.4 6
1 8
8.2 7
1 Nervous system
6 2.9
5 1
22 22.7
14 8
Accidents 5
2.4 3
2 3
3.1 3
Circulatory system 5
2.4 5
0.0 Tumours
3 1.4
3 0.0
Poisoning 1
0.5 1
0.0 Infectious diseases
0.0 1
1.0 1
Eye diseases 1
0.5 1
1 1.0
1 Miscellaneous
5 2.4
4 1
15 15.5
10 5
Unknown 29
13.9 27
2 26
26.8 11
15 Total
208 100.0
185 23
97 100.0
54 43
Table 10
be explained by the fact that mares have a value as
Numbers of deaths attributed to diseases of the musculoskeletal
breeding animals besides riding and competition,
system among warmblood horses in the Cavalry Horse Foundation
which geldings do not. It was shown in the study,
data
that a large proportion of the mares that participated
a
Site of disease injury Number
Percentage
in the RHQT also were used for breeding.
Joints 65
54.6
The brood-mares born between 1965 and 1967
Degenerative joint disease 62
52.0
were included in this study for the purpose of
Osteochondrosis 1
0.8
understanding more about length of life in mares.
Miscellaneous 2
1.7
This group was expected to live many years because
Skeleton 32
26.9
of minimum physical stress, compared with riding
Fractures 13
10.9
and competition horses. It was therefore interesting
Navicular disease 19
16.0
to see that mares, that participated in the RHQT and
b
Tendons 2
1.7
were born between 1968 and 1975, and used for
Undefined lameness 20
16.8
riding as well as breeding, had the same median
Total 119
100.0
length of life as brood-mares 18.3 and 18.6 years,
a
respectively, Table 6.
Percent of horses whose death was attributable due to diseases
There was also close agreement in the median
of the musculoskeletal system.
b
The cause was tendinitis in all cases.
length of life between the warmblood geldings born between 1970 and 1975 from the CHF, and males
that participated in the RHQT and that were born
5. Discussion between 1968 and 1975. The estimates were 14.7
