Anti-Docking Alliance (A.D.A.) |
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The Campaign Against the docking of dogs' tails (and cropping ears) |
February 1996
DENMARK
Report: the Animal Welfare Council regarding an assessment of reports on tail injuries.
On 30 November 1994, The Animal
Welfare Council submitted a letter with reference CAJ-0610 as well as enclosed
documents to the undersigned, requesting that ”...comments on the data and
their suitability are included in the assessment of departmental order no. 627
of 29/8/1991”. The enclosed documents consisted of 34 copies of completed
report forms, a note containing the total number of dogs treated at the
registered clinics during the second year of the study, and a copy of a letter
from the Animal Welfare Council to the minister of justice dated 27/9/1991 in
which the completed study is described:
”The
Animal Welfare Council recommends that the issuing of the aforementioned
departmental order is supplemented by a study comprising a sufficient number of
animal hospitals and animal clinics with the aim of registering existing canine
tail injuries over a period of at least two years – including the distribution
of injuries across different breeds.
The
Animal Welfare Council expects that such study, possibly supplemented by
Swedish and Norwegian experiences, will provide a firmer foundation for the
continuation or lifting of the departmental order. It is also expected that the
level of risk facing each breed will be documented with greater certainty than
that which is presently available”.
After some time, it
was discovered that, erroneously, only copies of report forms from the second
year of the study had been forwarded (1/10/93 – 30/9/94). Thus, in October
1995, I received a further 23 copies of completed report forms from the first
year of the study (1/10/92 – 30/9/93).
From
my understanding of the Animal Welfare Council’s enquiry, what is required is
the following:
1)
comments
on the data and their suitability for inclusion in the assessment of
departmental order no. 627 of 29/8/1991;
2)
an
assessment of injury incidence, including the distribution across different
breeds;
3)
an
illustration of the level of risk facing each breed.
Re 1): Comments on the data and their suitability for inclusion in the assessment of departmental order no. 627 of 29/8/1991
I
assume that the wording ”assessment of departmental order” refers in particular
to the assessment of the skewed incidence of tail injuries across breeds, which
can be documented as well as expected in pursuance of the departmental order’s
regulatory effect on the docking status of certain breeds, cf. items 2 and 3.
Comments
on the data and their suitability for these assessments may be divided into the
following subitems:
a)
Study
design
b)
Data
quality
c)
Data
scope (test sample size)
Re a) Study design
Besides
the total number of dogs treated at participating clinics/hospitals during the
second year of the study, only tail injury incidents are reported (a
”case-only” design), and so the data are primarily useful to describe the
incidents, whereas any analysis of comparable risk between for example docked
and non-docked breeds is limited. Nor is it possible to estimate tail injury
frequency on the basis of the received data.
It
is important to note that the ratios (for example in the form of percentages),
which in the present data can be calculated as the number of injuries divided
by the number of treated dogs, are numerical quantities (”proportional rates”)
that cannot be compared with actual injury frequencies. Such are to be
calculated on the basis of the number of animals within the actual canine
population that may incur the injuries (the ”risk population”, to be included
as the denominator). Interpretations of differences in proportional rates are
difficult, as the number of treated dogs only constitutes one part of the risk
population, and as many factors influence the composition and number of dogs
treated at participating clinics/hospitals.
The
applied design is therefore not suitable for actual numerical analyses. As a
minimum, and in addition to a record of the injuries, an analytical design
should have a record of breed and docking status of a comparable test sample of
dogs without tail injuries, which is chosen from, for example, other treated
dogs in the clinical data or from an existing canine register (”case-control”
design). Alternatively, the study could be carried out by following a number of
dogs of known and various breeds and docking status for a certain period of
time and registering new incidents of tail injuries (”cohort” design). A third
possibility is to investigate a large test sample of dogs of different breeds
in terms of the presence of tail injuries at the time of the investigation
(”cross section” design). In principle, these three types of analytical design
would all provide information about incidence and risk with respect to breed
and docking status, but they would entail different degrees of suitability and
significant differences in terms of practical possibilities.
Notably,
when assessing study design, any comparison between breeds and docking status
must take into account the fact that the change to the docking regulations was
introduced on 1/9/1991, and so non-docked individuals of breeds included in the
docking ban belong to certain, limited age groups, and the relevant age groups
change with each of the years during which the records take place. Comparisons
between breeds and docking status must therefore take into consideration the
age of the dogs, which means that a great number of the tail injuries to the
older dogs will not be included in this part of the calculations. The
analytical design must allow for this, and it will also influence the chances
of reaching the required number of examined dogs (cf. c)), as these will be
limited to the relevant age groups.
So,
several circumstances relating to the applied design means that one cannot draw
any real conclusions about the incidence and risks of tail injuries on the
basis of the present data.
Re b) Data quality
The
total of 57 completed record forms (23 submitted from the first year and 34
submitted from the second year) comprises:
Two forms with a
message from the relevant clinic that there were no diagnosed tail injuries
within the specified time period. Both originated from the same veterinary
hospital.
A
printout from one veterinary hospital with a very inadequate description of one
incident.
54
more or less completed forms of which two however turned out to be repeats of
one veterinary hospital’s first year submissions. (One of the copies even had
the year 1994 added after the date, though the copy of that same form was
submitted in 1993 without stating the year!).
Of
the remaining 52 forms, a good deal were incomplete as regards individual
pieces of information, for example date (four forms), the age of the dog
(totally absent on one form, and without any indication of
days/weeks/months/years on several others, entailing the risk of errors), and
the sex of the dog (91 forms). Of the 48 forms that were dated, four were dated
prior to the start of the first year (1/10/92) and two were dated after the end
of the second year (30/9/94).
This
sub-optimal data quality presumably reflects varying degrees of knowledge about
and co-responsibility for the study, its aim, character and premises, as well
as the fact that the recording and reporting at the hospitals/clinics often
involves several people.
Hence,
the present data are generally of sub-optimal or varying quality, which makes
actual analyses and conclusions open to doubt.
Re c) Data scope (test sample size)
From
the forwarded note, it emerges that the ten participating clinics/hospitals
treated approximately 70,000 dogs within a year. That same year records 26
incidents of tail injuries, which constitutes a minimal proportion of the
treated dogs (on average
approximately four incidents per 10,000 treated dogs) (see table 1). The
incidence of injuries is distributed across 20 stated breeds (se table 2). Only
a very comprehensive study can provide a statistically sound assessment of
differences between breeds for such relatively rare injury. A comparison of two
breeds, of which one is expected to be twice as much at risk of tail injuries
as the other, and where the incidence of the latter is expected to be like the
average (four per 10,000 treated dogs), should comprise 64,000 treated dogs
from each of the two breeds. In order for the difference to be statistically
sound, this is equivalent to an expectation of approximately 50 incidents of
tail injuries in the first breed and approximately 25 in the other. (Please
note that also breed, docking status and age of all dogs included in the study
should be registered and reported, and not just for the tail-injured dogs, cf.
a) above about design). In comparison, the breed with the greatest number of
reported tail injuries during the two years of available data is the German
Shepard with seven incidents (table 2). The number of German Shepherds among
all the treated dogs is unknown.
Hence,
the limited data sample size of the present data also means that one cannot
expect statistically sound conclusions.
Re 2) An assessment of injury incidence, including the distribution across different breeds
Table
1 shows the reported numbers distributed across the ten veterinary
hospitals/clinics and time period.
TABLE
1
PERIOD PERIOD
2
HOSPITAL 0 1 2 3 Total Total
treat. Prop. morb.*
-------------------------------------------------------------------------------------
ad 1 2 2 1 6 3000 7
bd 0 1 2 0 3 1800 11
dh 0 0 0 0 0 4500 0
dk 1 3 1 0 5 6500 2
gd 2 2 2 0 6 20000 1
hd 0 2 5 0 7 8423 6
ho 0 5 6 0 11 9000 7
kd 0 3 3 0 6 6500 5
rd 0 1 4 1 6 8000 5
sd 0 2 1 0 3 3200 3
-------------------------------------------------------------------------------------
Total 4 21 26 2 53 70923 4
* Proportional morbidity rate: Number of tail injuries per 10,000 treated dogs during PERIOD 2.
Table
2 shows the distribution of injuries across breeds, comparing those breeds that
have not been docked either prior to or after the introduction of the
departmental order (DOCK TYPE = 0) with those breeds that are illegal to dock
after 1/9/91 (DOCK TYPE = 1).
TABLE
2
DOCK TYPE
BREED 0 1 Total
-------------------------------------------------------------
Crossbreed 15 0 15
Boxer 0 1 1
Cocker
Spaniel 0 3 3
Dalmatian 4 0 4
Doberman 0 1 1
Field
Trial Spaniel 0 1 1
Flat-Coated
Retriever 2 0 2
Golden
Retriever 2 0 2
Grand
Danois 4 0 4
Dachshund 2 0 2
Irish
Setter 1 0 1
Short-Haired
Dachshund 1 0 1
Labrador Retriever 3 0 3
Long-Haired
Pointer 1 0 1
Wire-Haired
Dachshund 1 0 1
Wire-Haired
Pointer 0 1 1
Samoyed
Spitz 1 0 1
German
Shepard 7 0 7
Springer
Spaniel 0 1 1
West
Highland White Terrier 1 0 1
--------------------------------------------------------------
Total 45 8 53
However,
the two incidents reported for Boxer and Doberman are injuries to docked tails,
and so these two dogs are not included in the following assessments.
Moreover,
a Wire-Haired Pointer has been placed in DOCK TYPE = 1, as this dog is reported
as being non-docked, despite the fact that, according to the departmental
order, this breed is exempt from the docking ban.
Table
3 shows the 51 injuries to the non-docked dogs distributed across the four time
periods. It can be seen that, as expected, the proportion of dogs that are no
longer docked (DOCK TYPE 1) increases after the departmental order comes into
force.
TABLE 3
DOCK TYPE
PERIOD 0 1 Total
---------------------------------------------------------------------
0 4 0 4
100.0% 0.0%
1 18 2 20
90.0% 10.0%
2 22 3 25
88.0% 12.0%
3 1 1 2
50.0% 50.0%
---------------------------------------------------------------------
Total 45 6 51
88.2% 11.8%
Table
4 shows the age distribution of these injuries between the two types of canine
breeds. As expected, DOCK TYPE 1 tail injuries are only seen in young dogs (0-2
years) born after the departmental order came into force.
TABLE 4
DOCK
TYPE
AGE
(years) 0 1 Total
---------------------------------------------------------------------
< 1 5 4 9
55.6%
44.4%
1-2 3 1 4
75.0% 25.0%
2-3 6 1 7
85.7% 14.3%
3-4 3 0 3
100.0% 0.0%
4-5 11 0 11
100.0% 0.0%
5-6 4 0 4
100.0% 0.0%
6-7 2 0 2
100.0% 0.0%
7-8 1 0 1
100.0% 0.0%
8-9 3 0 3
100.0% 0.0%
9-10 3 0 3
100.0% 0.0%
11-12 2 0 2
100.0% 0.0%
13-14 1 0 1
100.0% 0.0%
UNKNOWN 1 0 1
100.0% 0.0%
----------------------------------------------------------------------
Total 45 6 51
88.2% 11.8%
Table
5.1-5.2 show the same as table 4, but for each of the actual two record periods
(the two periods with unsystematic records (PERIOD 0 and 3) are omitted here)
and only for those age groups that are relevant to the comparison, that is,
< 1 year for PERIOD 1 and 1-2 years for PERIOD 2.
Table
5.3 shows the sum of the two individual time periods. It can be seen that, when
taking into consideration the effects of age and time, half of the tail
injuries to non-docked dogs occurs in those breeds that have been included in
the docking ban. In other words, a rough estimate is that the number of tail
injuries treated at the participating clinics/hospitals will double from the
time prior to until the time after the departmental order coming into force,
where the entire age spectrum for tail injuries in all non-docked dogs is
represented (i.e. approximately year 2004). Due to the previously mentioned
circumstances, these estimates are however encumbered with considerable
uncertainty, and the present basis does not allow for further specification of
the size of this uncertainty. Moreover, one cannot be certain that the
underlying assumption will actually hold up, that is, that the age distribution
of injuries in the two DOCK TYPES will be the same.
TABLE 5.1
PERIOD
= 1: All dogs < 1 year at the time of treatment between 1/10/92 – 30/9/93
are born after 1/10/91.
DOCK TYPE
AGE
(years) 0 1 Total
-------------------------------------------------------------
<
1 2 2 4
50.0%
50.0%
TABLE 5.2
PERIOD
= 2: All dogs younger than two years at the time of treatment between 1/10/93 –
30/9/94 are born after 1/10/91.
DOCK TYPE
AGE
(years) 0 1 Total
--------------------------------------------------------------
<
1 2 2 4
50.0% 50.0%
1-2 1 1 2
50.0%
50.0%
PERIOD = 2: All dogs
younger than two years at the time of treatment between 1/10/93 – 30/9/94 are
born after 1/10/91.
TABLE 5.3
TOTAL
PERIOD 1-2: The sum of numbers from table 5.1 and 5.2
DOCK TYPE
AGE
(years) 0 1 Total
-------------------------------------------------------------
<
1 4 4 8
50.0%
50.0%
1-2 1 1 2
50.0%
50.0%
-------------------------------------------------------------
TOTAL 5 5 10 50.0% 50.0%
The
breed distribution of the six injuries among previously docked breeds
(including the previously mentioned Wire-Haired Pointer) is shown in table 6.
Though involving very few data, it should be noted that they are all breeds
used for hunting, whereas breeds as Boxer, Doberman etc. do not (yet) figure in
the statistic in terms of injuries among non-docked breeds. Moreover, one
individual clinic is apparently over-represented with four out of six
incidents.
TABLE 6
VETERINARY HOSPITAL
BREED ad hd ho Total
--------------------------------------------------------------------
Cocker
Spaniel 1 2 0 3
Field
Trial Spaniel 0 1 0 1
Wire-Haired
Pointer 0 1 0 1
Springer
Spaniel 0 0 1 1
--------------------------------------------------------------------
Total 1 4 1 6
Only
in the case of three out of the five dogs - where ”use” was completed - does it
state that it concerns a hunting dog. The remaining two are characterized as
”family dogs” (both Cocker Spaniels) (table 7).
TABLE 7
TYPE Freq
Percent Cum
---------------------------------------------------------
Hunting 3 60.0% 60.0%
Family 2 40.0% 100.0%
---------------------------------------------------------
Total 5 100.0%
Only
one of the six injuries had occurred during hunting, while four had occurred in
the home and one while being exercised (table 8).
TABLE 8
OCCURRED Freq
Percent Cum
------------------------------------------------------------------------
Hunting 1 16.7% 16.7%
Family 1 16.7% 33.3%
Home 4 67.5% 100.0%
------------------------------------------------------------------------
Total 6 100.0%
The
position of the tail injury is shown in table 9.
TABLE 9
POSITION Freq Percent Cum
------------------------------------------------------------------------
Tip 2 40.0% 40.0%
Caudal
1/3 3 60.0% 100.0%
------------------------------------------------------------------------
Total 5 100.0%
Table
10 shoes the nature of the injury. It is worth noticing that two incidents are caused by a parasitic infection
among newborn Cocker Spaniel puppies.
TABLE 10
NATURE Freq Percent Cum
------------------------------------------------------------------------
Deep
wound 1 66.7% 66.7%
Superficial 1 16.7% 83.3%
Other 4 16.7% 100.0%
------------------------------------------------------------------------
Total 6 100.0%
The
age of the injuries is shown in table 11.
TABLE 11
AGE
OF INJURY Freq Percent Cum
------------------------------------------------------------------------
Unknown 1 20.0% 20.0%
7
days 1 20.0% 40.0%
8
days 1 20.0% 60.0%
14
days 1 20.0% 80.0%
Over
100 days 1 20.0% 100.0%
------------------------------------------------------------------------
Total 5 100.0%
The
four oldest dogs had all had their tails docked, while one of the puppies was
put down (table 12).
TABLE 12
TREATMENT Freq
Percent Cum
------------------------------------------------------------------------
Amputation 4 66.7% 66.7%
Put
down 1 16.7% 83.3%
Unknown 1 16.7% 100.0%
------------------------------------------------------------------------
Total 6 100.0%
Re 3) An illustration of the
level of risk facing each breed
As
seen in 1), the nature, quality and scope of the data are insufficient to
secure statistically sound conclusions.
The
following, potentially interesting observations must therefore be viewed with
some reservation and merely as possible hypotheses that should undergo further
investigation at a later stage.
The
frequency of tail injuries is limited when they, as is the case here, are
calculated on the basis of records through veterinary treatments.
On the basis of the very slight data that relate to
incidents for animals born after certain breeds were included in the 1991
docking ban (ten incidents), there seems to be an overall incidence among these
breeds, which is equivalent to the number of incidents among the traditionally
non-docked breeds (five incidents within each group). Of the former breeds,
only the hunting dog types are represented among the tail injuries. Whether
these observations are significantly different than expected on the basis of
the breeds’ relative prevalence cannot be determined in this study. Hence, on
the basis of the existing data, one cannot throw any further light on the level
of risk facing the individual breeds.
Preben
Willeberg
dr.med.vet.,
dr.med.vet.h.c.
Professor
Veterinary
Forensic Medicine and Epidemiology
The Royal Veterinary and Agricultural University
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