Hindawi Publishing Corporation
International Journal of Zoology
Volume 2009, Article ID 563252, 6pages
Sand Floor for Farmed Blue Foxes: Effects on Claws,
Adrenal Cortex Function, Growth and Fur Properties
Leena Ahola, Tarja Koistinen, and Jaakko Mononen
Department of Biosciences, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland
Correspondence should be addressed to Leena Ahola, leena.ahola@uku.ﬁ
Received 22 May 2008; Revised 21 November 2008; Accepted 10 February 2009
Recommended by Marcel Eens
Farmed blue foxes (Vulpes lagopus) are traditionally housed on mesh ﬂoors where they are unable to perform certain species-
speciﬁc behaviours, such as digging, which may compromise the animals’ welfare. This study describes how a possibility to use
in-cage sand ﬂoor aﬀects welfare-related variables like growth of the claws, adrenal cortex function, and fur properties in juvenile
blue foxes. The foxes (N=32) were housed in male-female sibling pairs in an outdoor fur animal shed in cage systems consisting
of two traditional fox cages. For the eight male-female sibling pairs of the Control group, there was a mesh ﬂoor in both cages
of each cage system, whereas for the eight pairs of the Sand group there was a mesh ﬂoor in one cage and a 30–40 cm deep earth
ﬂoor in the other cage. The results show that sand ﬂoor is beneﬁcial for the wearing of the claws of foxes. Furthermore, an early
experience of sand ﬂoor may have positive eﬀects on the foxes’ fur development. The results, however, also suggest that there might
appear welfare problems observed as disturbed claw growth and increased adrenal cortex activation if foxes that are once provided
with clean and unfrozen sand ﬂoor are not allowed to enjoy this ﬂoor all the time.
Copyright © 2009 Leena Ahola et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
According to the nature-based approach to animal welfare
(see ), the welfare of production animals can be improved
by providing the animals with natural housing conditions
that enable them to behave species-speciﬁcally. However,
it is impracticable to provide production animals with
completely natural living conditions. Nonetheless, although
it may not be possible to allow production animals to live
in completely natural conditions, we still may provide them
with some important environmental features rooted in their
natural living environment. With respect to farmed blue
foxes (Vulpes lagopus,formerlyAlopex lagopus), one of these
important key features is the ﬂoor material used in their
Farmed blue foxes are traditionally housed in plastic
coated wire mesh ﬂoor cages. However, recent research has
shown that an earthen ﬂoor, a natural surface for the wild V.
lagopus, may have some importance for blue foxes (e.g., [2–
7]). However, recent research on the eﬀects of sand or earth
ﬂoors on the behaviour and physiology of blue foxes has
suﬀered from several confounding factors. In the previous
experiments, blue foxes have been farmed in male-male pairs
[8,9] or singly [4,6,10,11]whichdiﬀers from the normal
farming practices where foxes are housed most often in
male-female pairs. For example, single housing per se may
jeopardise the welfare of social animals , especially when
they are juvenile (for farmed silver foxes Vulpes vulpes see
). Therefore, in singly housed foxes, the eﬀects of an
earth ﬂoor on the animals’ welfare may be exaggerated due
to the fact that the animals are suﬀering social deprivation.
Other factors that may have confounded earlier experiments
have been reviewed in Koistinen et al. . Koistinen et al.
 assessed blue foxes’ behaviour and preferences (i.e.,
feelings-based welfare, see ) between a mesh ﬂoor and
a sand ﬂoor in a study where the ﬂaws of these previous
studies were corrected. Despite the modiﬁed study design,
the results of the study turnedouttobepractically
the same as the results from the earlier studies: blue foxes
preferred, based on their time allocation, the mesh ﬂoor to
the sand ﬂoor but nonetheless the sand ﬂoor seemed to have
at least some enrichment value for the foxes. This emerged
when the foxes with access to the sand ﬂoor were shown to
express less stereotypic behaviours than the foxes with access
2International Journal of Zoology
only to the mesh ﬂoor. Furthermore, a rebound-eﬀect was
observed in some behaviours on the sand ﬂoor (e.g., digging)
in the foxes with access to the sand ﬂoor after a sand ﬂoor
The present study that is a part of the study of Koistinen
et al.  continued to assess welfare eﬀects of continuous
access to sand ﬂoor under normal farming conditions in
farmed blue foxes. Whereas Koistinen et al.  assessed blue
foxes’ behaviour and preferences (i.e., feelings-based welfare,
see ) between mesh and sand ﬂoors, in this study we
evaluated how a sand ﬂoor experience or the lack of this
experience can aﬀect the blue foxes’ biological functioning
(functioning-based welfare, see ). First, we studied the
eﬀects of the sand ﬂoor on the growth of the claws. In the
wild, foxes’ claws wear down while, for example, digging
and walking on ground. On farms, however, claws of the
foxes that are housed on mesh ﬂoor do not wear and the
claws may grow very long . Long claws can become
caught in the mesh of the cage and break, exposing the
foxes to digit inﬂammations which impacts on both the
functioning-based and feelings-based welfare of the animals.
Therefore, the animal welfare legislation regulating farmed
fur animals  requires that the claws should be cut when
too long. Furthermore, the European Convention’s 
Recommendations concerning fur animals states that “animals
(foxes) will be kept in such way that their claws are in good
condition.” One way to ensure that those claws do not grow
too long is to provide the foxes with ﬂoor materials that
enhance the wearing of claws, for example, sand or earth.
Accordingly, we hypothesised that the possibility to interact
with sand ﬂoor could prevent the overgrowth of the foxes’
Secondly, we studied how the sand ﬂoor experience
aﬀects the stress physiology and production of the blue foxes.
Our hypothesis was that if sand ﬂoor was important for
the welfare of farmed blue foxes (i.e., as suggested by the
feelings-based results of the study ), the lack of sand ﬂoor
or the deprivation of a once-experienced sand ﬂoor would
increase the activity of the adrenal cortex (e.g., ) and
reallocate animals’ biological resources from growth and fur
development to coping with the stress .
Accordingly, the present study aimed to assess whether
sand could be used as a feasible ﬂoor material for farmed
foxes under normal farming conditions, without compro-
mising the welfare of these animals. Possible welfare-related
eﬀects were assessed by measuring the claw growth, adrenal
cortex function, growth and fur characteristics in the juvenile
blue foxes with access either to only a mesh ﬂoor or to both
a mesh and sand ﬂoors. The results will be discussed in the
light of the foxes’ behaviour during the present study .
2. Materials and Methods
The procedures used in the present study are in compli-
ance with the European Communities Council Directive
of 24 November 1986 (86/609/EEC). The experiment was
approved by the Institutional Animal Care and Use Commit-
tee of the University of Kuopio (Licence number 03-59).
2.1. Animals and Housing. There were 16 male-female sibling
pairs of farmed juvenile blue foxes, born in May, in the
present study. The foxes were housed throughout the study
in an outdoor fur shed. For the ﬁrst four weeks of their lives,
each pair was housed with its mother and other siblings as
a fox family in a traditional mesh ﬂoored fox cage (115 ×
105 ×70 cm, L ×W×H) furnished with a nest box, a
mesh platform, a wooden gnawing object, and a feeding
tray. When the cubs were four weeks old, the families were
divided randomly into two experimental groups. For both
experimental groups, cage systems were constructed from
two traditional fox cages that were connected together with
an opening (22.5×27.5cm, W ×H) through the walls
between the cages. In the Control group, the families were
housed from the cubs’ age of four weeks until the cubs’ age of
eight weeks in double cage systems where both available cages
had a mesh ﬂoor. In the Sand group, the families were housed
in double cage systems where the bottom of one cage was
made of mesh and the bottom of the other cage was replaced
with a 35–40 cm deep layer of sand (particle size <10 mm).
The nest boxes were removed from the cages at the cubs’ age
of seven weeks. At the cubs’ age of eight weeks, the mother
and other cubs except for the randomly chosen experimental
male and female cubs were removed from the double cage
systems; that is, thereafter there was only the male-female
sibling pair in each double cage system. Accordingly, there
were eight male-female sibling pairs in both the Control
group and the Sand group.
Since the present experiment studied also the foxes’
preferences for sand ﬂoor (see ), the foxes in the Sand
group were deprived of the sand ﬂoor for 14 days in early
September. During this deprivation period, each pair of
foxes in the Sand group had access to a double cage system
where both available cages had a mesh ﬂoor. The foxes in
the Control group had access to mesh ﬂoored double cage
systems during the whole study (for detailed description of
the deprivation procedure see ).
Dirty sand was removed from the sand ﬂoor and the sand
box was reﬁlled with clean sand immediately after weaning
and once in early October, soon after the deprivation period.
The health of the animals was checked daily. The foxes
were fed according to the recommendations given by the
Finnish Fur Breeders’ Association with fresh fur animal feed
twice a day until mid-November, thereafter once a day. The
daily feed portion per animal was the same for each group
and was delivered equally between the available cages. Water
was available ad libitum, except in subzero temperatures
(November-December) when fresh water was provided twice
2.2. Measured Parameters. Claw lengths (from the cuticle
to the claw tip) of all digits from the right front and back
paw were measured at the cubs’ age of eight weeks, in early
September (during the ﬁrst week of the 14-day deprivation
period), early October, early November, and at pelting in
mid-December. The numbers of broken claws in the right
early October, and at pelting in mid-December.
International Journal of Zoology 3
Body mass of the experimental foxes was measured at the
cubs’ age of eight weeks (i.e., at weaning in June-July), in
early October, and at pelting in mid-December.
Prior to pelting in mid-December, the foxes were injected
(1 mL i.m.) with synthetic corticotropin (ACTH) (0.25 mg
tetracosactide, Synacthen 0.25 mg/mL, Novartis Finland Oy,
Espoo, Finland). Two hours after the injection, the foxes
were euthanised by electrocution according to the methods
recommended by the Standing Committee of the European
Convention for the Protection of Animals Kept for Farming
Purposes . Blood samples were immediately drawn by
cardiac puncture. The serum cortisol level, as a maximum
response to ACTH administration [18,20], was analysed
with a competitive immunoassay technique (Coat-A-Count
Cortisol Assay by Diagnostic Products Corporation, Los
Angeles, Calif, USA).
After pelting, the adrenals were removed from the
carcasses, cleaned, and weighed. The pelts were ﬂeshed,
cleaned, dried, and sent for auction. Professional fur graders
at the Finnish Fur Sales Ltd (Helsinki, Finland) evaluated the
mass and overall quality of the furs using a 10-point scale (1:
poorest, 10: best).
2.3. Statistical Analyses. Statistical analyses were performed
using SPSS statistical software (SPSS for windows 14.0).
Since the two siblings in each double cage system were
dependent on each other, General Linear Model (GLM) for
repeated measures was used to analyse diﬀerences between
the groups in all measured variables. For the body mass
data, the Huynh-Feldt epsilon, a correction formula in the
GLM procedure in SPSS, was used in calculating the new
degrees of freedom and signiﬁcances in the within-subjects
eﬀects Month and Sex∗Month due to the sphericity problems
in these within-subjects eﬀects. Since the number of claw
breakages per animal was low in all measures, the data on
the number of broken claws was analysed as a sum variable
of claw breakages observed in both front and back paws in
September, October, and December. Thus, the maximum
possible number of claw breakages was 24 per animal. Since
the claw length did not diﬀer signiﬁcantly between the four
digits in the preliminary GLM model (P>.1), the claw
lengths were ultimately analysed using the mean length
of claws of all four digits. P-values smaller than .05 were
considered as statistically signiﬁcant, .1 <P<.05 as
tendencies and P>.1 as nonsigniﬁcant (NS).
No animals were found injured or sick during the whole
More claw breakages per animal were observed in the
Control group (3.9±1.7, mean ±standard deviation, SD)
than in the Sand group (1.3±1.2)(F(1, 14) =12.78, P=
.003). Sex had no signiﬁcant eﬀect on the total number of
observed claw breakages (2.4±2.9and2.8±1.6 breakages in
males and females, resp., F(1, 14) =0.33, NS). There was no
signiﬁcant interaction between the experimental group and
sex in the total number of claw breakages (F(1, 14) =0.59,
Sand Control Sand Control Sand Control
Figure 1: Body mass (kg, mean + SD) of juvenile blue foxes in the
Sand and Control groups at the cubs’ age of eight weeks (weaning),
in early October and at pelting (mid-December). Open bars: males,
solid bars: females. Main eﬀects (GLM for repeated measures):
Group F(1, 14) =0.64, NS; Sex F(1, 14) =9.78, P=.007; Month
F(2, 21) =489.54, P=.000; Sex∗Month F(1, 18) =7.50, P=.009,
other interactions NS.
There was no signiﬁcant main eﬀect of the experimental
group on the claw length (Tabl e 1). The males had longer
claws, especially in the Control group, than the females.
Furthermore, the claws were, in general, longer in the right
front paw than in the right back paw. The claws remained
shorter in the Sand group than in the Control group until
November-December. In the Control group, the claws of
the front paw grew until November and became shorter
thereafter whereas the claws of the back paw started to
shorten already in September-October. In the Sand group,
the claws of the front and back paw wore and grew steadily
and only a small decrease in the claw lengths was observed in
the Sand group in the October claw inspection compared to
the situation in September.
There was no statistically signiﬁcant diﬀerence in the
body mass of the animals between the Sand group and
Control group (Figure 1). In general, the males were heavier
than the females, especially at the end of the growing
The left adrenal was heavier in the Sand group than in
the Control group and in the males than in the females
(Figure 2). No signiﬁcant diﬀerences between the experi-
mental groups and sexes were observed in the mass of
right adrenal and the total mass of adrenals. There was no
signiﬁcant diﬀerence between the experimental groups and
sexes in the serum cortisol level after ACTH administration
(Sand group: 299±103 and 345 ±89 nmol/L in the males and
females, resp.; Control group: 308±108 and 314 ±68 nmol/L
in the males and females, resp., Group F(1, 14) =0.09, NS,
Sex F(1, 14) =0.65, NS, Sex∗Group F(1, 14) =0.38, NS).
The mass and overall quality of furs tended to be better
in the Sand group than in the Control group (Tabl e 2).
Furthermore, the mass and overall quality of furs was better
in the males than in the females. In particular, the females in
the Control group had poor mass and overall quality of furs.
The present results revealed that the foxes’ claws remained
shorter in the Sand group than in the Control group until
4International Journal of Zoology
Tab le 1: Mean claw length (mm, mean ±SD) of front and back right paw at weaning, in September, October, November, and December
in juvenile blue foxes in the Sand and Control groups. Main eﬀects (GLM for repeated measures): Group F(1, 14) =0.18, NS; Sex
F(1, 14) =7.60, P=.015; Month F(4, 56) =206.05, P=.000; Paw F(1, 14) =183.74, P=.000. Interactions: Sex∗Group F(1, 14) =3.50,
P=.082; Month∗Group F(4, 56) =4.06, P=.006; Paw∗Group F(1, 14) =20.19, P=.001; Paw∗Month F(4, 56) =2.94, P=.028;
Month∗Paw∗Group F(4, 56) =7.50, P=.000; other interactions NS.
Weaning September October November December
Male, front paw
Male, back paw
Female, front paw
Female, back paw
Tab le 2: Mass and overall quality of the furs (10-point scale; 1 =poorest, 10 =best; mean ±SD) of juvenile blue foxes in the Sand and
Sand Control Group Sex Group x Sex
Male Female Male Female
Mass (a) 6.1±1.25.4±1.25.6±1.83.6±1.3F(1, 13) =3.18 F(1, 13) =23.68 F(1, 13) =4.89
P=.098 P=.000 P=.045
Quality (a) 5.4±1.24.9±1.24.7±1.92.7±1.6F(1,13) =4.24 F(1, 13) =12.64 F(1, 13) =4.55
P=.060 P=.004 P=.063
(a) GLM for repeated measures.
Sand Control Sand Control
Figure 2: Mass (mg, mean + SD) of left (spotted bars) and right
(lined bars) adrenal and total mass of adrenals (black bars) of
juvenile blue foxes in the Sand and Control groups. Main eﬀects
(GLM for repeated measures): Left adrenal Group F(1, 13) =7.70,
P=.016, Sex F(1, 13) =5.88, P=.031, Sex∗Group F(1, 13) =
2.30, NS; Right adrenal Group F(1, 13) =0.70, NS, Sex F(1, 13) =
0.14, NS, Sex∗Group F(1, 13) =0.06, NS; Total mass of adrenals
Group F(1, 13) =2.97, NS, Sex F(1, 13) =1.52, NS, Sex∗Group
F(1, 13) =0.17, NS.
November. This result indicates that sand ﬂoor is beneﬁcial
in promoting the wearing of the claws. However, although
digging or walking on any rough ﬂooring wears the claws,
these activities also most probably increase the blood ﬂow
to the digits which in turn not only increases the growth
rate but also strengthens the claws (see ). The eﬀect of
diﬀerent kinds of activities on claw length was apparent in
the present study, that is, longer claws in the front than
in the back paw digits (similarly to the results in ).
Accordingly, when the foxes were able to manipulate the sand
ﬂoor or at least utilised the sand ﬂoor , the claws of the
foxes in the Sand group wore “naturally.” The (fast-growing)
claws of the Sand group foxes were then broken after (or
during the last week of) the sand ﬂoor deprivation period
in September. Thereafter the claws of the Sand group foxes
again grew and wore “naturally.” This continued until the
sand ﬂoors were becoming soiled with faeces and frozen in
November-December. At that time, the Sand group foxes
spent signiﬁcantly less time on the sand ﬂoor than in
September (on the sand ﬂoor 2.0±0.5and11.1±2.1%
of all observations in December and September before the
deprivation period, resp., ). In December, the claws did
not wear but continued to grow rapidly due to the earlier
stimulation. As a result, in December the claws of the Sand
group foxes were longer than the claws of the Control group
foxes. Accordingly, our hypothesis that sand ﬂoor would be
beneﬁcial for the wearing of the claws was correct, but only
with one proviso: sand ﬂoors are beneﬁcial for the claw
health and growth only if the foxes are permanently provided
with the kind of sand ﬂoor that the foxes are willing to utilise.
International Journal of Zoology 5
The eﬀects of sand or earth ﬂoors on the adrenal cortex
activity in blue foxes have been assessed in earlier studies
by measuring the total mass of adrenals (e.g., [10,11]). In
general, no signiﬁcant diﬀerences have been detected in the
total adrenal mass between foxes with and without access to
an earth ﬂoor. However, there is evidence that it is the left
adrenal in particular that is more sensitive to stressful events
or stressful conditions [22–24]. Here we found that the left
adrenals were heavier in the Sand group foxes than in the
Control group foxes. Accordingly, this result suggests that the
foxes in the Sand group had experienced more stress than the
foxes in the Control group. It could be hypothesised that the
Sand group foxes experienced the sand ﬂoor as an aversive
surface. One indication in support of this proposal might be
that the Sand group foxes were seen on the sand ﬂoor cage in
less than 20% of the total observations . In the Control
group, in contrast, the observations were evenly distributed
between the two available cages. However, one must bear in
mind that the Sand group foxes were never forced to stay on
the sand ﬂoors, they always had access to the mesh ﬂoor,
too. Furthermore, mere time allocation between available
options is an insuﬃcient basis on which to draw conclusions
about animals’ needs (see ). Therefore, another, more
likely explanation is that the increased left adrenal mass in
the Sand group was attributable to the lack of the clean
and unfrozen sand ﬂoor in the latter part of the study
period. In other words, when the sand ﬂoor was clean and
unfrozen, the foxes were able or willing to perform diﬀerent
activities in the sand, for example, digging, scratching, and
observations from the total observations of these behaviours
were observed to occur on the sand ﬂoor . When the
sand ﬂoor became soiled and frozen in December, the Sand
group foxes spent less time on the sand ﬂoor than previously,
and less than 25% of the total observations of digging or
scratching and sniﬃng behaviours occurred on the sand
ﬂoor . The hypothesis that it was the lack of (clean
and unfrozen) sand ﬂoor that enlarged the foxes’ adrenals is
supported by the observation of a rebound-eﬀect in digging
and sniﬃng behaviour when these foxes were reunited with
this resource after the deprivation period in September ,
that is, the animals place value on access to a clean sand ﬂoor.
Accordingly, the present result on the adrenal mass, as well as
the feelings-based welfare results , suggests that if farmed
blue fox cubs are once provided with a clean and unfrozen
sand ﬂoor, they should be allowed to enjoy this ﬂoor for
the rest of their lives (cf. digging in farmed blue foxes, ).
This could, however, prove to be impossible or at least highly
demanding to implement in northern climates with subzero
temperatures during the long winter months.
The ACTH challenge test did not reveal any signiﬁcant
diﬀerences between the experimental groups in their adrenal
cortex activities. This apparent discrepancy between the
adrenal mass and ACTH challenge test results is not a unique
ﬁnding in welfare studies (see, e.g., [25,26]). Furthermore,
in the present study, the animals were injected with the
more rapidly acting Synacthen instead of the more slowly
acting Synacthen Depot that has been used earlier in studies
focusing on the welfare of farmed foxes (e.g., [20,25]); that
is, the true peak cortisol concentration may have occurred
already before the blood samples were drawn. Therefore, the
present ACTH challenge test results should be evaluated with
With regard to the measured production variables, there
were no statistical diﬀerences in the body masses of the
foxes in the two experimental groups. The Sand group foxes
tended to have better mass and overall quality of furs than
the Control group foxes. Blue foxes start to replace their
summer coat with a new winter pelage already in August
; that is, the foxes have to be prepared to invest their
biological resources in fur development throughout their
growing season. The slightly better mass and overall quality
of furs in the Sand group foxes might suggest that the Sand
groupfoxescouldaﬀord to invest their resources in fur
development and growth during their early lives, that is,
from August onwards, whereas the Control group foxes were
investing more of their resources in coping (see for
discussion about the “biological cost of stress”) with their
every-day-lives, including the housing environment without
a possibility to interact with sand ﬂoor.
In conclusion, the present results suggest that access
to sand ﬂoor is beneﬁcial for the wearing of the claws of
blue foxes. Furthermore, an early experience of sand ﬂoor
may have positive eﬀects on the animals’ fur development.
However, these results also suggest that if foxes are once
provided with clean and unfrozen sand ﬂoor, they should
be allowed to have access to this kind of ﬂoor all the time.
Otherwise there may be welfare problems such as disturbed
claw growth and increased adrenal cortex activation. It may
prove to be impossible or at least highly demanding to allow
foxes to enjoy access to clean and unfrozen sand ﬂoor under
the normal fox farming practices in northern climates with
subzero temperatures for several months.
The authors wish to thank the anonymous reviewers for
their constructive comments. The study was supported by
the Fur Animal Welfare Council and Finnish Fur Breeders’
Association. The authors are grateful to the staﬀof the
research station for animal care, to Martti Hallikainen, Maija
Miskala, Teija Pyyk¨
onen, and Antti Turunen for practical
assistance on the farm and Hobo Kukkonen for laboratory
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