Influence of different combinations of racing years on early career performance in trotters


Saastamoinen, M.T.; Ojala, M.

Acta Agriculturae Scandinavica. Section A Animal Science 44(4): 208-213

1994


The aim of this study was to investigate the frequencies of young trotters and differences in their racing performance in various 'starting age - career length' (SACL) combinations. The annual race records were summarized to provide early career records for two- to five-year-old Standardbred trotters (n = 3080) and three- to six-year-old Finnhorse trotters (n = 2638). The majority (85.7%) of Standardbred trotters started racing at the age of three or four years. Most Finnhorse trotters (76.0%) had their first race as four- or five-year-olds. The most common SACL-combination was the three- to five-year-old season in Standardbred trotters and four- to six-year-old season in Finnhorse trotters, respectively. A statistically significant interaction between the SACL-combination and sex was observed for best career time. Generally, horses starting their racing career young and racing during several consecutive years were superior to other horses in both breeds. Standardbred trotters racing through three to five years of age had career times 5.6, 7.5 and 6.3 seconds better on an average than horses racing only as three-, four- or five-year-olds, respectively. In Finnhorses the differences between the SACL combinations pointed in the same direction and were even greater.

Acta
Agric.
Scand,
Sect.
A,
Animal
Sri.
1994:
44,203-213
Copyright
43
Arta
Agricuhuriz
Srand.
1994
Printed
in
Denmark
.
All
rights
reserved.
Influence
of
Different
Combinations
of
Racing
Years
on
Early
Career
Performance
in
Trotters
ACTA
AGRICULTURiE
SCANDINAVICA
ISSN
0906-4702
Saastamoinen,
M.T.
(Agricultural
Research
Centre,
Equine
Research,
FIN-
32100
Ypaja,
Finland)
&
Ojala,
M.
(University
of
Helsinki,
Department
of
Animal
Science,
PO
Box
28,
FIN-00014
Helsinki,
Finland).
Influence
of
different
combinations
of
racing
years
on
early
career
performance
of
trotters.
Accepted
April
5,
1994.
Acta
Agric.
Scand.,
Sect.
A,
Animal
Sci.
44:
208-213,
1994.
©
Acta
Agric.
Scand.
1994.
The
aim
of
this
study
was
to
investigate
the
frequencies
of
young
trotters
and
differences
in
their
racing
performance
in
various
'starting
age
career
length'
(SACL)
combinations.
The
annual
race
records
were
summarized
to
provide
early
career
records
for
two-
to
five-year-old
Standardbred
trot-
ters
(n=3080)
and
three-
to
six-year-old
Finnhorse
trotters
(n=2638).
The
majority
(85.7%)
of
Standardbred
trotters
started
racing
at
the
age
of
three
or
four
years.
Most
Finnhorse
trotters
(76.0%)
had
their
first
race
as
four-
of
five-year-olds.
The
most
common
SACL-combination
was
the
three-
to
five-year-old
season
in
Standardbred
trotters
and
four-
to
six-year-old
sea-
son
in
Finnhorse
trotters,
respectively.
A
statistically
significant
interac-
tion
between
the
SACL-combination
and
sex
was
observed
for
best
career
time.
Generally,
horses
starting
their
racing
career
young
and
racing
during
several
consecutive
years
were
superior
to
other
horses
in
both
breeds.
Standardbred
trotters
racing
through
three
to
five
years
of
age
had
career
times
5.6,
7.5
and
6.3
seconds
better
on
an
average
than
horses
racing
only
as
three-,
four-
or
five-year-olds,
respectively.
In
Finnhorses
the
differences
between
the
SACL
combinations
pointed
in
the
same
direction
and
were
even
greater.
Markku
T.
Saastamoinen'
and
Matti
Ojala
2
'Agricultural
Research
Centre,
Equine
Research,
FIN-32100
VOA,
Finland
and
2
University
of
Helsinki,
Department
of
Animal
Science,
PO
Box
28,
FIN-00014
Helsinki,
Finland
Key
words:
horse,
environmental
factors,
racehorse,
trotting.
Introduction
Performance
results
recorded
during
the
early
ca-
reer
of
trotters
can
be
used
in
breeding
evaluation
in
several
ways.
For
example,
in
Finland
(Ojala,
1989)
and
in
the
Netherlands
(Minkema,
1989)
the
evaluation
is
based
on
annually
summarized
race
records
of
individual
age
classes.
Summarized
data
over
age
classes
are
used
for
breeding
evaluation
of
trotters
in
Sweden
and
Norway
(Arnason
&
Svendsen,
1991).
The
use
of
early
career
records
(i.e.
results
sum-
marized
over
certain
age
classes)
instead
of
indi-
vidual
age
class
records
makes
it
possible
to
in-
clude
all
those
offspring
of
a
sire
that
have
raced
at
certain
ages
simultaneously
in
the
breeding
evaluation.
However,
the
career
records
of
a
trotter
consist
of
various
combinations
of
age
class
rec-
ords
(racing
years)
because
of
differences
in
start-
ing
age
and
absence
of
some
racing
years.
It
is
a
known
fact
that
the
age
of
the
horse
has
a
large
influence
on
its
racing
results.
There
are
many
reasons
for
a
career
record
to
include
various
numbers
and
combinations
of
age
class
records.
Many
factors
influence
the
possi-
bility
to
begin
the
career
at
young
age
and
to
race
during
many
consecutive
seasons
(Bendroth,
1981;
Klemetsdal
et
al.,
1985;
Physick-Sheard,
1986a;
Saastamoinen,
1991a;
1991b).
It
is
also
presumable
that
culling
of
untalented
and
unsound
horses
by
their
owners
and
trainers
increases
with
the
age
of
horses
because
of
the
large
costs
of
horse-keeping.
Further,
owners
may
withdraw
their
horses
from
races
at
any
age
owing
to
accidents
or
for
any
other
reason.
The
aim
of
this
study
was
to
quantify
the
influ-
208
ence
of
various
combinations
of
racing
years
on
early
career
records
in
Finnish
Standardbred
and
Finnhorse
trotters.
Material
and
methods
The
data
consisted
of
annually
summarized
race
records
of
two-
to
five-year-old
Standardbred
trot-
ters
born
in
Finland
between
1981
and
1984,
and
three-
to
six-year-old
Finnhorse
trotters
born
be-
tween
1980
and
1983.
The
total
number
of
horses
included
in
the
study
comprised
3080
Stan-
dardbred
trotters
and
2638
Finnhorses.
The
annual
race
records
were
summarized
to
provide
early
career
results
for
two-
to
five-year-
old
Standardbred
trotters
and
three-
to
six-year-
old
Finnhorse
trotters.
The
traits
used
to
represent
a
horse's
early
career
performance
were:
square
root
of
number
of
starts,
best
time
on
volt-start,
fourth
root
of
earnings
and
earnings
per
start,
and
logit
of
number
of
first-to-third
placings.
A
de-
scription
and
the
means
of
these
traits
have
been
presented
by
Saastamoinen
&
Ojala
(1991).
Starting
age
and
number
of
racing
years,
i.e.
length
and
continuity
of
the
career
of
a
horse,
were
arranged
into
"starting
age
-
career
length"
(SACL)
combinations
(Table
1).
A
racing
year
equals
a
calendar
year
for
three-year-old
and
older
Standardbred
trotters,
and
for
four-year-old
and
older
Finnhorses,
whereas
two-year-old
Stan-
dardbred
and
three-year-old
Finnhorse
trotters
are
allowed
to
start
racing
after
the
first
of
July
in
the
year
when
they
are
two
and
three
years
old,
respec-
tively
(Anon.,
1987).
The
age
of
a
horse
is
counted
Racing
performance
in
young
trotters
from
the
first
of
January
of
the
birth
year
(Anon.,
1987).
Some
SACL
combinations
were
deleted
from
the
statistical
analyses,
because
the
number
of
records
in
them
was
very
small.
Consequently,
the
SACL
combinations
used
in
the
statistical
analyses
in-
cluded
eight
classes
for
Standardbred
trotters
(Table
2)
and
ten
for
Finnhorse
trotters
(Table
3).
On
an
average,
52
and
59%
of
Standardbred
trotters
and
Finnhorses
were
males
(stallions
or
geldings),
respectively
(Table
1).
However,
in
the
SACL
combination
'3+4'
in
Standardbred
trotters
and
'4+5'
in
Finnhorses,
the
proportion
of
males
was
only
40%.
The
data
were
analyzed
by
the
least
squares
(LS)
analysis.
The
following
linear
model
was
assumed
in
analyzing
the
data
within
the
two
breeds:
Yijkl=p+ai+bi+abii+ck+eijki
where
Yijkl
is
the
early
career
record
of
the
/th
horse;
µ
is
the
general
mean;
a
;
is
the
fixed
effect
of
the
ith
"starting
age
-
career
length"
(SACL)
combination;
b
j
is
the
fixed
effect
of
jth
sex;
(IN
is
the
interaction
between
the
ith
SACL
com-
bination
and
jth
sex;
Ck
is
the
fixed
effect
of
the
kth
year
of
birth;
eijkl
is
a
random
residual,
NID
(0,62e)•
The
effects
of
sex
by
year
of
birth,
and
year
of
birth
by
SACL
combination
interactions
were
also
Table
1.
Distribution
of
horses
among
different
'starting
age
-
career
length'
(SACL)
combinations
Standardbred
trotters
Finnhorse
trotters
SACL
combination
Male
Female
Total
SACL
combination
Male
Female
Total
2
-
- -
0.0
3
5
3
8
0.2
2+3
1
3
4
0.0
3+4
14
17
31
1.0
2+4
- - -
0.0
3+5
1
1
0.0
2+5
1
-
1
0.0
3+6
1
1
0.0
2+3+4
7
7
14
0.5
3+4+5
13
24
37
1.5
2+3+5
2
-
2
0.0
3+4+6
9
6
15
0.5
2+4+5
1
1
2
0.0
3+5+6
6
3
9
0.3
2+3+4+5
27
26
53
2.0
3+4+5+6
157
62
219
8.0
3
48
36
84
2.5
4
63
48
111
4.0
3+4
98
139
237
7.5
4+5
89
135
224
9.0
3+5
13
10
23
1.0
4+6
32
25
57
2.0
3+4+5
664
527
1191
38.5
4+5+6
611
303
914
35.0
4
90
102
192
6.0
5
75
52
127
5.0
4+5
482
433
915
30.0
5+6
313
249
562
21.5
5
177
185
362
12.0
6
161
161
322
12.0
Total
1611
1469
3080
1550
1088
2638
209
M.
T.
Saastamoinen
and
M.
Ojala
Table
2.
Influence
(LS
deviations)
of
'starting
age
-
career
length'
(SACL)
combination
on
career
racing
performance
in
Standardbred
trotters
SACL
combination
No.
of
horses'
ST
BT
MR
IS-mean
3080
4.03
83.94
8.94
4.27
-1.22
2+3+4+5
53
2.87
-4.31
6.76
1.68
0.15
3
84
-1.75
2.42
-3.01
-0.59
0.07
3+4
237
-0.19
0.19
-0.08
0.14
-0.11
3+5
.
23
-0.51
-0.94
0.06
0.45
0.09
3+4+5
1191
2.40
-3.17
4.02
0.83
0.16
4
192
-1.99
4.32
-4.66
-1.51
-0.09
4+5
914
0.66
-1.23
0.88
0.23
-0.04
5
361
-1.50
3.10
-3.84
-1.23
-0.22
'Regarding
best
time
on
volt-start
the
total
number
of
horses
was
3057.
ST=(no.
of
starts)
172
;
BT=best
time
on
volt
start
(s/km);
M=(earnings)
1
/
4
;
MR=(earnings/race)
1
/
4
;
P=logit
of
first-to-third
placings.
Table
3.
Influence
(LS
deviations)
of
'starting
age
-
career
length'
(SACL)
combination
on
career
racing
performance
in
Finnhorse
trotters
SACL
combination
No.
of
horses'
ST
BT
MR
LS-mean
2638
3.71
104.62
7.17
3.46
-1.31
3+4
31
-1.02
3.54
-1.99
-0.44
-0.36
3+4+5
37
0.65
-2.62
1.44
0.54
-0.09
3+4+5+6
219
3.01
-8.80
5.43
1.36
0.16
4
111
-2.02
11.20
-5.08
-2.04
0.05
4+5
223
-0.18
0.56
-0.28
0.01
-0.12
4+6
57
-0.12
-0.77
0.44
0.38
0.05
4+5+6
914
2.22
-7.60
4.41
1.26
0.16
5
127
-1.83
7.27
-3.79
-1.27
0.08
5+6
561
-0.57
-3.47
1.60
0.69
0.02
6
320
-1.27
1.80
-2.17
-0.51
0.05
'Regarding
best
time
on
volt-start
the
total
number
of
horses
was
2600.
ST=(no.
of
starts)"
2
;
BT=best
time
on
volt
start
(Vim);
M=(earnings)
141
;
MR=(earnings/race)"
4
;
P=logit
of
first-to-third
placings.
included
in
the
statistical
models,
but
these
interac-
tions
were
not
found
to
be
statistically
significant,
and
thus
were
ignored.
Results
and
discussion
Distribution
of
horses
in
different
'starting
age
-
career
length'
subclasses
The
majority
(85.7%)
of
Standardbred
trotters
started
racing
at
the
age
of
three
or
four
years.
Most
Finnhorse
trotters
(76.0%)
had
their
first
race
as
four-
or
five-year-olds.
Only
2.5%
of
the
Standardbred
trotters
raced
as
two-year-olds.
The
percentage
of
Finnhorse
trotters
that
raced
as
three-year-olds
was
12.1%.
These
small
percen-
tages
are
as
expected,
since
horses
are
allowed
to
start
racing
after
the
first
of
July
in
the
year
when
they
are
two
(Standardbreds)
and
three
(Finnhors-
es)
years
old.
In
addition,
only
a
limited
number
of
races
are
available
in
Finland
for
horses
at
these
ages.
Consequently,
the
first
race
year
has
only
a
minor
impact
on
the
career
performance
even
for
horses
having
raced
at
the
earliest
possible
ages.
About
80%
of
the
horses
in
both
breeds
had
more
than
one
racing
year
during
their
early
ca-
reer.
A
horse
was
defined
as
having
raced
if
it
had
at
least
one
start
during
some
of
the
possible
ra-
cing
years
of
the
study
period.
A
total
of
38.5%
of
the
Standardbred
trotters
and
35.0%
of
the
Finnhorses
had
a
career
ex-
tending
from
three-
to
five-year-
and
four-
to
six-
year-olds,
respectively
(Table
1).
These
were
the
most
common
SACL
combinations
in
the
two
breeds
in
this
data
set.
Owing
to
the
previously
mentioned
rules
for
harness
racing,
horses
in
these
combinations
can
be
considered
to
have
had
"a
full
career".
The
second
most
common
SACL
combi-
nation
was
four-
to
five-year-olds
in
Standardbred
trotters
(30.0%)
and
five-
to
six-year-olds
in
Finnhorses
(21.5%).
The
third
most
common
SACL
combination
for
both
breeds
was
the
last
age
class.
210
Racing
performance
in
young
trotters
The
above
observations
imply
that
starting
the
career
as
early
as
possible
does
not
have
particular
emphasis
in
the
Finnish
trotting
sport.
This
is,
in
part,
due
to
traditions
and
also
to
the
fact
that
most
horses
are
broken
and
trained
by
their
breed-
ers
or
owners,
who
want
to
spare
their
horses
to
allow
for
an
assumed
longer
career.
Horses
broken
and
trained
by
professional
trainers
were
found
to
start
earlier
than
other
horses
(Saastamoinen,
1991b),
and
may
be
considered
more
talented
and
developed
than
the
other
horses.
The
average
length
of
the
early
career
was
2.2
years
in
Standardbred
trotters
and
2.3
years
in
Finnhorse
trotters.
For
both
breeds,
the
career
was
somewhat
longer
in
males
than
in
females,
which
agrees
with
the
results
of
Physick-Sheard
(1986b).
Effect
of
starting
age
and
career
length
on
career
performance
The
'starting
age
career
length'
(SACL)
combi-
nation
had
a
statistically
significant
(p<0.001)
in-
fluence
on
all
career
performance
traits,
except
on
the
number
of
first-to-third
placings
in
Finnhorses.
In
general,
horses
that
started
racing
young
and,
furthermore,
that
raced
during
sev-
eral
consecutive
years,
were
found
superior
to
the
other
horses
(Tables
2
and
3;
Fig.
1).
The
results
improved
with
the
increasing
number
of
consecu-
tive
racing
years
also
within
the
starting
age
group.
The
best
career
results
were
in
horses
having
a
full
four-year
career
(Tables
2
and
3).
They
had
the
largest
number
of
starts,
and
partly
due
to
this,
also
the
best
career
time
and
highest
career
earnings.
The
number
of
horses
in
this
group
was
small,
especially
in
Standardbred
trotters.
Horses
having
a
full
three-year
career
formed
the
most
common
SACL
combination
in
this
data
set,
and
their
performance
was
almost
as
good
as
was
ob-
served
for
horses
in
the
previous
group.
Standardbred
trotters
racing
at
the
ages
of
three
to
five
years
had
career
times
1.9
s
better
on
an
average
than
horses
in
the
SACL-class
'4+5',
the
second
most
common
SACL
combination
(Table
2).
The
career
times
of
horses
with
a
full
three-year
career
were
also
on
an
average
about
5.6,
7.5
and
6.3
s
better
than
of
horses
that
raced
only
as
three-,
four-
or
five-year-olds,
respectively.
The
differences
reflect,
in
part,
differences
in
the
number
of
starts
between
the
horses
in
these
groups.
The
order
between
the
SACL
classes
was
similar
also
for
the
other
performance
traits
in
this
study.
The
differences
between
the
corre-
sponding
SACL
combinations
in
Finnhorses
were
Time
sec.
90
85
80
75
2+3
4+6
3
3+4
3+5
3+4+5
4
4+5
6
SACL-combination
a
Males
Females
Time
sec.
120
115
110
105
100
96
8
4
3.4.6
8.4.6.6
4
4.6
4.8
4.6.8
6
6.6
e
SACL-combination
b
Males
Females
Fig.
1.
Influence
of
'starting
age
-
career
length'
(SACL)
combi-
nation
on
best
time
on
volt-start
in
(a)
Standardbred
trotters
and
(b)
Finnhorse
trotters.
similar
and
even
greater
than
in
Standardbred
trotters
(Table
3).
Among
Standardbred
trotters
having
results
only
from
one
racing
year,
the
best
racing
results
were
in
three-year-old
starters,
which
was
the
smallest
SACL
class
among
these
horses
(Table
2).
The
superiority
of
three-year-old
starters
for
the
best
career
time
compared
to
four-
and
five-year-
old
starters
may
be
due
to
their
higher
precocity
and
better
talent.
However,
these
horses
discon-
tinued
their
careers
for
some
reason
as
opposed
to
the
delayed
starting
age
of
five-year-old
starters.
The
inferiority
of
five-year-old
starters
was
poss-
ibly
due
to
lack
of
talent
and
inferior
soundness,
and
they
could,
therefore,
not
benefit
from
their
older
age.
There
were
no
large
differences
in
the
number
of
starts
between
the
horses
in
these
three
age
groups.
In
the
case
of
finnhorses
that
raced
only
during
one
race
year,
the
best
career
time
was
found
to
improve
with
age
(Table
3).
The
superiority
of
Finnhorses
that
raced
only
as
five-
or
six-year-
olds
compared
to
horses
racing
at
four
years
of
age
may
be
due
to
general
age-related
factors,
such
as
maturity
and
superiority
of
an
older
to
a
younger
age
(Ojala
&
Hellman,
1987).
There
may
211
M.
T.
Saastamoinen
and
M.
Ojala
also
be
pressure
to
compete
more
frequently
with
an
'old'
horse
to
compensate
the
losses
resulting
from
a
delayed
starting
age,
as
implied
by
the
larger
number
of
starts
of
six-year-old
starters
compared
to
four-
and
five-year-old
starters.
In
addition,
it
is
possible
that
the
number
of
untal-
ented
horses
withdrawn
grew
as
starting
age
in-
creased,
as
reported
for
Canadian
trotters
by
Physick-Sheard
(1986b).
Sex
by
'starting
age
career
length'
interaction
In
the
case
of
best
career
time
on
volt-start,
there
was
a
statistically
significant
interaction
between
the
SACL
combination
and
sex
both
in
Stan-
dardbred
trotters
(p<0.001)
and
in
Finnhorses
(p<0.05).
Of
the
Standardbred
trotters
racing
as
three-year-olds
and
through
their
three-to-four-
year-old
seasons,
females
had
a
better
time
record
than
males
(Fig.
la).
The
difference
between
the
sexes
was
largest
(1.8
s)
in
horses
that
raced
only
as
three-year-olds
(SACL
class
3).
In
Finnhorses
the
difference
between
the
sexes
was
largest
(3.0
s),
in
favour
of
females,
for
horses
racing
at
all
ages
during
their
three-
to
five-year-old
seasons
(Fig.
lb),
and
only
marginal
in
the
SACL
class
4+5.
In
the
rest
of
the
SACL
combinations,
males
were
52.9
and
:55.6
s
faster
than
females
in
Stan-
dardbred
and
Finnhorse
trotters,
respectively.
This
observation
is
supported
by
several
previous
studies.
These
results
should
be
taken
with
some
reser-
vations,
because
the
largest
differences
in
favour
of
females
were
observed
in
the
SACL
classes
that
had
only
a
small
number
of
observations.
If
true,
the
interaction
may
reflect
a
kind
of
'early
speed'
in
females
compared
to
males.
Another
expla-
nation
may
be
that
the
intention
of
the
owners
was
to
get
good
results
for
mares
at
a
young
age
before
withdrawing
them
from
training
and
transferring
to
breeding,
while
males
were
kept
in
training
and
racing
as
long
as
possible.
It
has
been
reported
in
previous
studies
that
males
start
their
career
earlier
and
have
a
longer
career
than
females
(Physick-
Sheard,
1986a;
Saastamoinen,
1991a;
Saastamoin-
en
&
Ojala,
1991).
General
discussion
and
conclusions
Differences
in
the
performance
of
trotters
in
vari-
ous
'starting
age
career
length'
combinations
were
obviously
influenced
by
the
number
of
starts.
Horses
that
began
their
career
young
and
con-
tinued
it
for
several
years
had
the
opportunity
to
start
more
often
and,
thus,
also
more
often
in
ideal
conditions,
resulting
in
better
career
performance.
They
may
also
have
been
precocious,
as
well
as
sounder
and
more
talented
than
their
contempor-
aries.
On
the
other
hand,
horses
that
started
late
and
raced
only
during
a
few
years
had
fewer
op-
portunities
to
achieve
good
results.
All
of
these
horses
should
not
be
regarded
as
untalented
or
late
maturing,
because
several
environmental
factors
have
been
reported
to
influence
the
starting
age
of
a
horse
(Bendroth
et
al.,
1981;
Saastamoinen,
1991a).
Such
factors
may
also
be
the
reason
for
discontinuing
the
career.
Further,
it
is
known
that
traits
such
as
number
of
starts
and
age
at
the
be-
ginning
of
the
career
have
a
low
heritability
(Arna-
son
et
al.,
1989;
Saastamoinen
&
Ojala,
1991).
These
traits
and
length
and
continuity
of
the
career
greatly
depend
on
the
intentions
of
the
owners
and
trainers,
as
well
as
on
injuries
and
accidents
to
which
a
horse
may
have
been
subjected
during
training
and
racing.
The
influence
of
the
'starting
age
career
length'
combination
on
the
early
career
performance
of
the
trotters
was
considerable.
The
majority
of
the
horses
had
a
full
three-year
career
or
a
career
con-
sisting
of
two
consecutive
race
years.
The
best
ca-
reer
performance
was
observed
for
horses
in
these
SACL
combinations.
Thus,
if
the
breeding
evalu-
ation
of
trotters
is
based
on
early
career
records,
horses
starting
their
career
young
and
racing
sev-
eral
years
are
favoured.
This
implies
that
there
is
no
need
to
adjust
the
career
results
for
the
effects
of
starting
age
and
career
length.
References
Anon.,
1987.
Ravikilpailusa5nnot
[Rules
for
harness
races].
Suomen
Hippos,
Helsinki,
72
pp.
Arnason,
T.,
Bendroth,
M.,
Philipsson,
J.,
Henriksson,
K.
Dar-
enius,
A.
1989.
Genetic
evaluation
of
Swedish
trotters.
In:
State
of
breeding
evaluation
of
trotters.
EAAP
Publication
no.
42.
NVageningen,
pp.
106-130.
Arnason,
T.
&
Svendsen,
M.
1991.
Application
of
animal
model
of
trotters
in
Scandinavia.
Proc.
42nd
Ann.
Meet.
Eur.
Assoc.
Anim.
Prod.
13
pp.
Bendroth,
M.
1981.
A
survey
of
reasons
for
some
trotters
being
non-starters
as
2-,
3-
and
4-year
olds.
Proc.
36th
Ann.
Meet.
of
Eur.
Assoc.
for
Anim.
Prod.
5
pp.
Klemetsdal,
G.,
Svendsen,
M.
&
Vangen,
0.
1985.
Preliminary
results
from
genetic
studies
of
racing
performance
in
Nor-
wegian
trotters.
Proc.
36th
Ann.
Meet.
of
Eur.
Assoc.
for
Anim.
Prod.
10
pp.
Minkema,
D.
1989.
Breeding
evaluation
of
trotters
in
the
Netherlands.
In:
State
of
breeding
evaluation
of
trotters.
EAAP
Publication
no.
42.
Wageningen.
pp.
82-94.
Ojala,
M.
1989.
Breeding
evaluation
of
trotters
in
Finland.
In:
State
of
Breeding
evaluation
of
trotters.
EAAP
Publication
no.
42.
Wageningen.
pp.
18-26.
Ojala,
M.
&
Hellman,
T.
1987.
Effects
of
year,
sex,
age
and
breed
on
annually
summarized
race
records
for
trotters
in
Finland.
Acta
Agric.
Scand.
37,463-468.
Physick-Sheard,
P.
W.
1986a.
Career
profile
of
the
Canadian
Standardbred.
II.
Influence
of
age,
gait
and
sex
upon
number
212
of
races,
money
won
and
race
times.
Can.
J.
Vet.
Res.
50,
457-470.
Physick-Sheard,
P.
\V.
1986b.
Career
profile
of
the
Canadian
Standardbred.
I.
Influence
of
age,
gait
and
sex
upon
chances
of
racing.
Can.
J.
Vet.
Res.
50,449-456.
Saastamoinen,
M.
T.
1991a.
Factors
affecting
age
at
onset
of
breaking,
training,
qualifying
and
first
start
in
Finnish
trot-
ters.
Acta
Agric.
Scand.
41,137-145.
Racing
performance
in
young
trotters
Saastamoinen,
M.
T.,
1991b.
Some
factors
of
the
time
of
breaking
and
training
affecting
racing
performance
in
young
trotters.
J
Agric.
Sci.
Finl.
63,483-492.
Saastamoinen,
M.
T.
&
Ojala,
M.
1991.
Estimates
of
genetic
and
phenotypic
parameters
for
racing
performance
in
young
trotters.
Acta
Agric.
Scand.
41,427-436.
213