Accumulation of dietary fish fatty acids in the body fat reserves of
some carnivorous fur-bearing animals

Kirsti Rouvinen, Jaakko Mäkelä, Tuomo Kiiskinen and Seppo Nummela

Rouvinen, K., Mäkelä, J.,Kiiskinen, T. & Nummela, S. 1992. Accumulation ofdietary
fish fatty acids in the body fat reserves of some carnivorous fur-bearing animals.
Agric. Sei. Finl. I: 483-489. (Agric. Res. Centre of Finland, Fur Farming Res. Sta.,
SF-69100 Kannus, Finland, Finnish Fur Breeders’ Association, P.0.80x 5, SF-01601
Vantaa, Finland, Agric. Res. Centre of Finland, Inst. Anim. Prod., SF-31600 Jokioinen,
Finland and Agric. Res. Centre ofFinland, Centr. Lab., SF-31600 Jokioinen, Finland.)

Body fat composition of the mink (Mustela vison), polecat (Mustela putorius), and the
raccoon dog (Nyctereutes procyonoides) was studied. The animals were fed a wet diet,
supplemented with 5 % lard (LA) or fish oil (FO) for 5-6 months. At pelting, five
animals per dietary group were sampled. Dietary levels of cetoleic (C22:1 to 11), eico-
sapentaenoic (EPA, C20:5<03), and docosahexaenoic (DHA, C22:6c03) acids were 0.4,
0.3, and 0.5% in the fat of the LA diet, and 7.6,4.2 and 4.3% in the FO diet, respectively.
In the FO diet, EPA and DHA accumulated especially in the liver and heart, while
cetoleic acid showed the highest affinity to the heart muscle and subcutaneous fat. The
highest levels of EPA were found in raccoon dogs and polecats fed the FO diet. The
mean EPA levels ranged from6.7-9.3% in the liver fat and 7.2-8.0% in the heart muscle
fat. In the mink, the corresponding values were 2.7% and 3.9%, respectively. DHA
levels were the highest in the liver fat of the polecats, being 18.5% in the FO diet. In
addition, the liver in raccoon dogs fed the FO diet (13.8%) differed significantly from
the mink (9.4%). The differences in the accumulation of these long-chained marine fatty
acids were apparently caused by species differences in the efficiency of their peroxi-
somal (1-oxidation.

Key words: ferret, mink, polecat, raccoon dog, cetoleic acid, omega-3 fatty acids, liver,
heart, subcutaneous fat

Introduction

In monogastric animals, dietary fat has a strong
influence on the fatty acid composition of the
tissues and organs. Feeding vegetable oils and fish
oils to mink and blue foxes has been shown to
increase the levels of linoleic and omega-3 fatty
acids, respectively, in the fat depots and the liver of

the animals (Rouvinen and Kiiskinen 1989,
Skrede and Gulbrandsen 1985, Skrede 1984,
Ahman 1965). In blue and silver foxes, feeding an
abundance of fish fat is known to cause prominent
accumulation of the typical fish fatty acids, i.e.
cetoleic (C22: Icol 1), eicosapentaenoic (EPA,
C20:5c03) and docosahexaenoic (DHA, C22:6c03)
acids, in their subcutaneous fat, liver tissue and

483

Agric. Sei. Fint. 1 (1992)

https://www.c-info.fi/en/info/?token=bet-PUiJXaazECS_.9uCZD7kvrmStoNcBwMI_Vg.xRRAOlJiGAaJpMe54EeQycFSqHDWa-bEbS5om-Ao4IssfDsm6djhjJFby4XEOi6uzugPfRDZG1iQNqTNQ85dSaVM6K8eYZ2ZDFJI3dupIuUHzCSZZptzYdX9Q6VGUN3qWjltQ_RRzFiaEJfqk_-0Vnn8YtAlkzLt3_Pk16g0FiDSHFtK2tDsHXayZy8zReVDNbmzJQB0TMtf-RDp6gWfKrd1MwQ5z4UCa25uhCb8eViec0cP7_KijN97Bqw_WIk6whWmjYzuciTOweHOtrFF9Hr978WfYSToejnApJP4FS9Ipzg1bQslyUHfX6PxA6KnU0B9TW4EOtPM_4ny4WefrFDm


heart muscle (Rouvinen 1991, Rouvinen 1992).
In the rat, feeding fish oil or high erucic acid
(C22;1c09) rapeseed oil has been shown to cause
lipid infiltration, cell destruction, local inflamma-
tory reactions and fibrous scar tissue growth in the
heart muscle (Beare-Rogers 1977, Kjnsella

1987). Accumulation of these long-chained fatty
acids in body tissues is apparently due to their
impaired oxidation. The 20 or 22 carbon atom-
chained fatty acids should first be shortened in the
peroxisomes to 16 or 18 carbon atom-fatty acids
before they can be metabolized by the mitochon-
drial p-oxidation (Opstvedt 1984).

The present paper reports the effects of feeding
lard or fish oil supplemented diets on the body fat
composition of some farm-raised carnivorous fur-
bearing animals, mink, polecat and the raccoon dog.

Material and methods

Mink (Mustela vison), polecats (Mustela putorius)
and raccoon dogs (Nyctereutes procyonoides) were
fed diets based on slaughterhouse offal, fish offal
and cereals supplemented either with lard (LA) or
fish oil (FO), at 5% in the diet. The animals used
were all bora during the spring of 1988, and were
raised according to normal fur farming practices at
the Veikkola Research Farm of the Finnish Fur
Breeders’ Association, Kirkkonummi. The trial
lasted from July until pelting during the autumn of
1988. Composition of the experimental diets is

presented in Table 1. Feed samples for chemical
analysis were taken on August 23rd, and on Sep-
tember 30th. Fatty acid composition was analyzed
from feed samples taken on November 30th.

Five animals per dietary group were electrically
executed for sampling on November 30th, 1988. At
sampling, the age of the animals was approximately
6-7 months. The mink and polecats were all males,
but the raccoon dogs included both sexes, two
males and three females per group. The animals
were weighed and sampled for liver fat analysis,
and samples for fatty acid analysis were taken from

Table 1.Composition of experimental diets from weaning to
pelting 1988. LA = lard diet, FO = fish oil diet.

Diet

Ingredient, % LA FO
Slaughterhouse offala) 15 15
Fish offal 30 30
Fish meal 1 1
Soybeanmeal 0.5 0.5
Com gluten I 1
Blood meal 1 1
Cereals b) 13 13
Vitamins0* 1.5 1.5
Lard 5
Fish oil - 5
Water 32 32
a) LSO slaughterhouse, Forssa
1,1 cooked cereal: wheat 50 % and barley 50 %.

c) 1 kg mixture contains; vitamin A, 500 000 IU; vitamin
Ds, 50 000 IU; vitamin C, 6 000 mg; vitamin E, 4 000 mg;
vitamin K, 10 mg; vitamin Bi, 1 500 mg; vitamin 82,600
mg; vitamin 812, 1 mg; choline, 2 500 mg; pantothenic
acid, 500 mg; nicotinic acid, 1 000 mg; pyridoxin, 400 mg;
folic acid, 50 mg; and biotin, 3 mg.

therump region of the carcasses (subcutaneous fat),
the liver and the heart. The weights of the sampled
organs were also taken. The feed, tissue and fat
samples were stored at -30°C until analyzed be-
tween January 4th and March 13th, 1989.

The experimental diets were analyzed for dry
matter (DM), ash, Kjeldahl nitrogen and crude fat.
The analyses were performed by the Feed Laborat-
ory of theFinnish Fur Breeders Association, Vaasa.
Fatty acid composition of the diets and the tissue
samples were determined in the Central Laboratory
of the Agricultural Research Centre ofFinland. The
method employed is described in detail by Rou-
vinen (1991). The liver fat content was determined
by the method of Maxwell et al. (1980) at the
laboratory of the Institute of Animal Production,
Animal Nutrition Section, Jokioinen.

Statistical analysis was performed by the General
Linear Models (GLM) procedure of the Statistical
Analysis System (SAS 1988). The model used was
as follows:

484

Agric. Sei. Fin!. 1 (1992)



Yijk n + Sj + Dj + SDjj + Cijk

where p is the general mean, Sj is the species effect
(/ = 1-3), Dj is the dietary effect (j = 1-2), SD.j
represents the species diet interaction and eijk is the
error term. Differentiation among the mean values
was done by Duncan’s multiple-range test. There
were no statistical differences (p>0.05) between
sexes in the fatty acid composition of the tissue
samples taken from the raccoon dogs, therefore the
means given represent pooled data from both sexes.

Results

Chemical composition of the experimental diets
was similar in lard (LA) and fish oil (FO) sup-
plemented groups (Table 2). Dietary fat content was
high, 27-30% in DM, whichaccounted for approxi-
mately 50% of the metabolizable energy in both
dietary groups.

Dietary fatty acid composition showed a great
difference between the lard and fish oil sup-
plemented diets (Table 3). The lard diet contained
more stearic (C18;0) and oleic (C 18:1co9) acids, but
in the fish oil diet the content of cetoleic
(C22: Icol 1), eicosapentaenoic (C20:5c03) and do-

Table 2. Chemical composition of the diets during the growth
period 1988. Diets sampled on Aug. 23rd and Sept. 30th.
LA =lard, FO = fish oil, DM = dry matter.

Diet
August September

Analyzed LA FO LA FO
DM, % 30.2 30.1 31.2 30.9

In DM, %

Ash 7.3 6.6 6.4 7.4
Protein 31.1 33.9 30.8 35.0
Fat 29.1 28.6 30.4 26.9
Carbohydrates10 32.5 30.9 32.4 30.7

a) calculated as difference.

cosahexaenoic (C22;6c03) acids was considerably
higher.

Body weights of the animals and the weights of
the liver and the heart did not differ between the
dietary treatments. The body weights for the mink,
polecats and the raccoon dogs were on average
2249 g, 2055 g, and 8709 g. The average weights of
the liver and (heart) were 48.6 g, (10.6 g), 57.9 g,
(8.5 g), and 208.7 g (32.7 g) for the mink, polecat
and the raccoon dog, respectively. There were no
species diet interactions.

Clear species differences were found in the liver
fat content and body fat composition of the animals
(Table 4). Besides higher fat content in the mink
livers the variation in the fat content was consider-
ably higher for this species. Dietary background of
the animals did not affect the liver fat content.

The fatty acid composition of the tissue samples
strongly reflected the fatty acid profile of the diet-
ary fats in all species and in all fat and organ
samples studied (Table 4). Furthermore, interesting

Table 3. Fatty acid composition of the diets. Determination
ofsamples taken on Nov. 30th, 1988. LA = lard diet,
FO = fish oil diet.

Fatty acids
°/n in fat

Diet
% in fat FOLA
C14:0 5.32.5
C 16:0 22.826.1

24.0C18:0 8.6
Saturated
Cl6: lto7
C18: lto9
C20:1t09

36.952.9
2.4 5.4

22.633.7
1.0 6.6

C22:1c09+ll 1) 0.4 7.6
Monounsaturated
C18:3w3

42.837.7
1.30.8

0.2 1.7C18:4c03
C20:5c03
C22:6<03
Omega-3
C18:2c06
C20:4c06
Omega-6

0.3 4.2
4.30.5

12.31.9
7.1 7.5

0.20.2
8.07.5

11erucic acid (C22:1c09) and cetoleic acid (C22: Icol 1)not
separated in the fatty acid analysis.

485

Agric. Sei. Finl. 1 (1992)



Table 4. Liver fat content and the content ofcetoleic, eicosapentaenoic and docosahexaenoic acids in the liver tissue, heart
muscle and subcutaneous fat of the mink, polecat and the raccoon dog fed two different diets, LA =lard, FO = fish oil.
ND = not detected. Presented are means ± S.D.

Fatty acids Mink Polecat Raccoon dog Significance

% in fat LA FO LA FO LA FO Species Diet S x D

Liver
Fat % 13.7 a 11.8 a 7.3 b 5.1 b

±4.4 ±7.0 ±l.O ±0.6

C22:1w9+ll 1) 0.2 d I.oa o.2cd 0.6 b
±O.O ±O.l ±O.O ±O.l

C20:5c03 0.4 e 2.7 d 2.2 d 6.7 b
±O.l ±0.9 ±0.4 ±l.l

C22:6c03 2.9 d 9.4 c 8.4 c 18.5 a
±0.6 ±2.2 ±1.4 ±0.9

Heart
C22:1(09+l 1 0.2 d 2.5 b 0.4 d 1.5c

±O.l ±0.7 ±0.2 ±0.2

C20:5c03 I.lc 3.9 b 2.9 b 7.2 a
±O,l ±1.2 ±0.7 ±0.5

C22:6c03 6.Bbc 7.9 b 7.9 b 11.4a
±0.7 ±1.9 ±1.3 ±l.l

Subcutaneous fat
C22:1c09+1l 0.3 c 3.2 b 0.2 c 3.5ab

±O.l ±0.6 ±O.l ±0,5

C20:5<03 ND 0.9 b 0.3 c 1.5a
ND ±0.3 ±O.O ±0.2

C22:6t03 0.5 d 2.4 c l.Od 4.2 a
±O.l ±l.l ±O,l ±0.5

4.3b 4.9b <O.OOl NS NS
±0.2 ±0.4

ND 0.4c <O.OOl <O.OOl <O.OOl
ND ±O.O

4.1c 9.3a <O.OOl <O.OOl <O.OOl
±0.4 ±0.5

8.2c 13.8b <O.OOl <O.OOl <O.Ol
±1.6 ±l.O

0.4d 3.1a <O.OOl <O,OOl <O.OOl
±O.l ±0.5

1.6c B.oa <O.OOl <O.OOl <O.OOl
±0.7 ±l.l

2.2d 5.5c <O.OOl <O.OOl <0,05
±0.6 ±0.3

0.4c 3.9a NS <O.OOl NS
±O.l ±0.3

0.3c 1.5a <O.OOl <O.OOl NS
±O.l ±0.2

0.9d 3.2b <O.OOl <O.OOl <0.05
±0.3 ±0.3

a-e: means within rows having different postscripts are significantly different (p<0.05) 11 see Table 3.

differences between the individual fish fatty acids
in their affinity to certain fat depots in different
species were observed. In the FO diet, cetoleic acid
accumulated especially in the heart muscle and the
subcutaneous fat, while its levels in the liver fat
were comparatively low. The highest levels ofceto-
leic acid were found in the heart and subcutaneous
fat of the raccoon dogs. Moreover, in all species
studied the accumulation of EPA and DHA was
more prominent in the liver and heart tissue than in
the subcutaneous fat. The highest levels of EPA
were found in the tissues of the raccoon dogs and
polecats fed the FO diet. In addition, the polecats
and raccoon dogs fed theFO diet had significantly

higher levels of DHA in their livers than did the
mink or the corresponding animals receiving the
LA diet. The DHA levels in heart were the highest
in polecats fed the FO diet.

Discussion

Fatty acid profiles of the lard and fish oil sup-
plemented diets differed greatly reflecting the com-
position of the supplemental fat. Both feed mixtures
contained, however, a considerable amount of fish
offal, which contributed to omega-3 fatty acids in
both diets.

486

Agric. Sei. Fint. 1 (1992)



The accumulation of the polyunsaturated omega-
-3 fatty acids was prominent in the fish oil diet forall
fur animal species included in this study. There
were also significant species differences, polecats
and raccoon dogs having remarkably higher con-
tents of these fatty acids in their tissues and espe-
cially in the liver than the mink. These results are in
agreement with earlier studies with mink and blue
fox (Rouvinen and Kiiskinen 1989),and with blue
and silver foxes (Rouvinen 1991, Rouvinen
1992). The blue foxes fed a fish oil supplemented
diet tended to concentrate more omega-3 fatty acids
in their livers than the mink (ROUVINEN and KIIS-
KINEN 1989),while in silver fox livers the levels of
these fatty acids were even higher than in blue foxes
when the animals were fed the same diet (ROU-
VINEN 1991, Rouvinen 1992). In the earlier study
(Rouvinen 1991), the fat accumulation pattern dif-
fered between the fish oil and saturated fat diets. In
the fish oil diet, the fat was present in the liver in
small droplets, which was considered to be un-
physiological. In addition, the degenerative change-
s observed were more numerous and severe in this
dietary group (ROUVINEN 1991).

It is interesting to note that the levels of DHA in
the liver and heart tissues were very high also for
the LA diet. This may suggest that even very low
amounts of dietary DHA will accumulate in these
tissues. In addition, significant species differences
could be observed with the lowest amount of DHA
found in the liver of the mink, whereas in the heart
the lowest amount was found in the raccoon dog.
Moreover, despite equal amounts of DHA and EPA
withinboth diets, the accumulation of DHA was in
nearly all cases much more severe than ofEPA. The
22 carbon chain of DHA could simply be more
difficult to shorten to 16 or 18 carbons compared to
EPA molecule with only 20 carbon atoms.

In the rat, dietary erucic acid and its omega-11
isomer, cetoleic acid, have been shown to cause
lipid infiltrationand tissue degeneration in the heart
muscle (Beare-Rogers 1977, Kinsella 1987).
Several cases of unexplained cardiac failure have
recently been reported in Finnish silver foxes

(SMEDS 1992). In the 1980’s, during the years of
intensive fox production, the dietary composition of
the wet fiir animal feed has changed considerably.
Meat and slaughter offal based ingredients have
been replaced by fish offal and industrial fish dueto
their more affordable price. Moreover, the use of
fish oil as a cheap energy supplement has increased.
It is thus reasonable to believe that there may be a
connection between the accumulation of the long-
chained marine fatty acids, especially cetoleic acid,
in the silver fox heart tissue and the pathological
condition observed. Support to this hypothesis may
also be found from a recent work on blue fox
vixens, where long-termfish feeding prior to breed-
ing and suckling period was shown to increase pup
mortality (ROUVINEN and NIEMELÄ 1992).

The key enzymes of the peroxisomal and mito-
chondrial [3-oxidation are the fatty acyl-CoA oxi-
dase (FAO) and carnitine palmitoyl transferase
(CPT), respectively. Their activities reflect the ca-
pacities of the corresponding oxidation pathways
(Moves et al. 1991). The peroxisomal (3-oxidation
is known to be induced when the diet contains high
fat levels or fatty acids which are poor substrates for
mitochondria (MOVES et al. 1991). In species, such
as seals and salmon, which normally encounter
polyunsaturated fatty acids in their diets, the mito-
chondria are, however, better capable to oxidize
long-chained unsaturated fatty acids (Moves et al.
1991). In the rat, feeding marine oils is known to
induce the peroxisomal (3-oxidation. This is con-
sidered to be the response of an omnivore to spe-
cific fatty acids which are not normally obtained in
the diet. It is essentially a detoxification response
(Moves et al. 1991).

It is very likely that the differences in the accu-
mulation of the long-chained marine fatty acids
found in the present study are caused by species
differences in the efficiency of the peroxisomal (3-
oxidation. This is apparently a consequence of
adaptation to certain food sources during the evol-
utionary development of the different fur animal
species (Nelson and Ackman 1988). Unlike the
foxes (Dekker 1983, Fay and Stephenson 1989),

487

Agric. Sei. Fin!. 1 (1992)



raccoon dog (Mäkelä and Kiiskinen 1978) and
polecat (Fox 1988), the mink seems to be well
capable of utilizing the long-chained polyunsatu-
rated fatty acids due to its adaptation to a semi-
aquatic habitat (Kyne et al. 1989,Tolonen 1982).
Therefore, the other farm-raised carnivorous fur-
bearers should not be fed fatty fish or fish oil in
excess, since the 20 and 22 carbon-atom fatty acids
are more readily accumulated in the tissues and
organs of these species. The present results suggest
that more emphasis should be placed on a species

specific formulation of the diets for the farm-raised
fur animals.

Acknowledgements. The Finnish Ministry ofAgriculture and
Forestry is thanked for financially supporting this study. The
authors are grateful to Mr. Tapani Ratilainen, and to the staff
of the Veikkola Research Farm for taking care of the animals
and helping with the sampling, and to the staffs of the labor-
atories of the Finnish Fur Breeders Association in Vaasa, and
the Institute of Animal Production, Animal Nutrition Sec-
tion, in Jokioinen, for carrying out the analyses. The kind
help ofMr. Steven Alward, B.Sc., inchecking the English of
the typescript is also greatly appreciated.

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Manuscript received July 1992

Kirsti Rouvinen
Agricultural Research Centre ofFinland
Fur Farming Research Station
SF-69100 Kannus, Finland

Present address:
Nova Scotia Agricultural College,
Department os Animal Science,
P.0.80x 550, Truro,
Nova Scotia, B2N 5E3 Canada

Jaakko Mäkelä
Finnish Fur Breeders’ Association,
P.0.80x 5, SF-01601 Vantaa, Finland

Tuomo Kiiskinen
Agricultural Research Centre ofFinland,
Institute of Animal Production
SF-31600 Jokioinen,Finland

Seppo Nummela
Agricultural Research Centre ofFinland
Central Laboratory
SF-31600 Jokioinen,Finland

SELOSTUS

Rehun kalaperäisten rasvahappojen kertyminen eräiden lihaasyövien
turkiseläinten ruhon rasvavarastoihin

Kirsti Rouvinen, Jaakko Mäkelä, TuomoKiiskinen ja Seppo Nummela
Maatalouden tutkimuskeskus ja Suomen Turkiseläinten Kasvattajain Liitto ry

Minkeillä ja siniketuilla rehun kasviöljylisäyksen tiedetään
lisäävän linolihapon määrää jakalaöljytäydennyksen puoles-
taan omega-3 rasvahappojen pitoisuutta elimistössä. Sini- ja
hopeaketuilla kalarasvaruokinnan on todettu aiheuttavan
tyypillisten kalarasvahappojen, kuten ketoleeni-, eikosapen-
taeeni- (EPA) ja dokosaheksaeenihappojen (DHA) kerty-
mistä nahanalaisrasvakudokseen, maksaan ja sydänlihak-
seen. Rehun kalarasvatäydennyksen tai erukahappopitoisen
rypsiöljyruokinnan tiedetään myös aiheuttavan rotalla rap-
peutumamuutoksia sydänlihaksessa.

Tässä selostetussa tutkimuksessa selvitettiin minkin, hil-
lerin ja supikoiran ruhon rasvakoostumusta. Eläimiä ruokit-
tiin 5-6 kuukauden ajan joko laardilla tai kalaöljyllä täyden-
netyllä, kalaan ja teurasjätteeseen pohjautuvalla rehuvaliolla.
Rasvalisä rehussa oli 5 % tuorepainosta. Laardirehussa keto-
leeni-, EPÄ- ja DHA-pitoisuudet olivat 0.4, 0.3 ja 0.5 %

rehun rasvassa. Vastaavat tasot kalaöljyrehussa olivat 7.6,
4.2 ja 4,3 %. Kustakin ryhmästä tutkittiin viisi eläintä. Eläi-
mistä otettiin näytteet maksasta, sydänlihaksesta ja nahana-
laisrasvakudoksesta rasvahappoanalyysiävarten.

Kaikilla tutkituilla eläinlajeilla ruhon rasvakoostumus
riippui voimakkaasti rehun rasvakoostumuksesta. Ka-
laöljyrehulla EPÄ jaDHA varastoituivat erityisesti maksaan
ja sydänlihakseen,kun taas ketoleenihappopitoisuudet olivat

korkeimmat sydänlihaksessa ja nahanalaisrasvassa. Kor-
keimmat EPA-pitoisuudet analysoitiin kalaöljyrehulla ruo-
kittujen supikoirien ja hillereiden kudoksista. Pitoisuudet
vaihtelivat 6.T-9.3 % maksan rasvassa ja 7.2-8.0 % sydänli-
haksen rasvassa. Minkeillä vastaavat pitoisuudet olivat ai-
noastaan 2.7 % ja 3.9 %. DHA-pitoisuudet olivat korkeim-
mat kalaöljyllä ruokittujen hillereiden maksakudoksessa
(18.5 %). Lisäksi supikoirien maksojen DHA-pitoisuudet
(13.8 %) olivat merkitsevästi minkkien arvoja korkeammat
(9.4 %).

Tutkittujen pitkäketjuisten kalarasvahappojen kertyminen
kudoksiin on todennäköisesti seurausta niiden riittämättö-
mästä peroksisomaalisesta P-oksidaatiosta elimistössä. Evo-
lutiivisen kehityksensä aikana eri eläinlajit ovat sopeutuneet
parhaiten hyödyntämään tiettyjä ravintolähteitä. Puoliksi ve-
sielämään sopeutuneena lajina minkki näyttää pystyvän hyö-
dyntämään kalalle tyypillisiä, pitkäketjuisia, monityydytty-
mättömiä rasvahappoja muita tässä tutkittuja tarhaturkiseläi-
miä paremmin. Saatuihin tuloksiin perustuen kalaöljyn
käyttöä rehun yksinomaisena rasvalähteenä ketun, supi-
koiran ja hillerin rehussa tulisi välttää. Enemmän huomiota
tulisi kiinnittää myös lajikohtaiseen rehuvaliosuunnitteluun
tarhatuilla turkiseläimillä.

489

Agric. Sei. Fin!. 1 (1992)