Educare Agust 2014.indb

EDUCARE:
International Journal for Educational Studies, 7(1) August 2014

About the Authors: Prof. Hannu T. Korhonen, Ph.D. and Paavo Niemelä, Ph.D. are Principal Research Scientist and Docent in
Applied Zoology at the MTT Agrifood Research Finland, Animal Production Research, Silmäjärventie 2, FIN-69100 Kannus, Finland.
For academic purposes, corresponding author is: hannut.korhonen@mtt.fi

How to cite this article? Korhonen, Hannu T. & Paavo Niemelä. (2014). “Digestibility of Heat Treated Barley in Blue Fox and Mink”
in EDUCARE: International Journal for Educational Studies, Vol.7(1) August, pp.43-48. Bandung, Indonesia: Minda Masagi Press and
UMP Purwokerto, ISSN 1979-7877. Available online also at: http://educare-ijes.com/digestibility-of-heat-treated/

Chronicle of the article: Accepted (March 20, 2014); Revised (May 30, 2014); and Published (August 17, 2014).

INTRODUCTION
Carbohydrates are cheap and easy

accessible material for feed in animal
production (Berg, 1986; Pölönen, 2000; and
Nenonen & Pölönen, 2002). Barley, which
mainly contains carbohydrates, has become
more popular as an ingredient in fur animal
feed. However, digestibility of barley varies
in different fur animal species. This obviously
holds true also for farm-raised canid and
mustelid species. Further research on this
subject is needed, however.

The blue fox (vulpes lagopus) is a colour type
of wild Arctic fox. Thus, medium-size canid
is farm-raised for its excellent fur coat. As a
carnivore, it generally can utilize carbohydrates
fairly well. The composition of the diet of wild
foxes typically varies seasonally and regionally
(Frafjord, 1993; and Angerbjörn et al., 1994).
In an Arctic habitat, foxes tend mainly to eat
meat and food scraps; whereas in a coastal

area, their diet may comprise mainly fish
(Nielsen, 1991). Foxes have, therefore, adapted
to marked regional, annual, and seasonal
fluctuations in food availability and content.
See picture 1.

The mink (neovison vison), on the other
hand, is a small-sized mustelid having an
elongated body shape (Korhonen & Huuki,
2013). Due to high surface-to-mass ratio, the
mink has to sustain higher basal metabolic
rate than other mammals of the same body
weight (Brown & Lasiewski, 1972; Iversen,
1972; and Korhonen, Harri & Asikainen,
1983). The mink typically utilize carbohydrates
considerably poor. This is due to very short
digestibility tract which results a short transit-
period of only 4-5 hours (Sibbald et al., 1962;
and Jorgensen ed., 1985). Furthermore, the
production of carbohydrate decomposing
enzyme seems to be modest in the mink
(Ostergaard, 1998). See picture 2.

HANNU T. KORHONEN & PAAVO NIEMELA

Digestibility of Heat Treated Barley
in Blue Fox and Mink

ABSTRACT: Carbohydrates are easy accessible raw material for fresh feed in domestic animal production. Barley,
which mainly contains carbohydrates, has become more popular as an ingredient in feed for fur bearing animals
in particular. The aim of the present study was to clarify the effects of heat treatment on digestibility of barley
in farm-raised juvenile blue fox and mink. Two different heat treatments were compared here: (1) traditional heat
treatment; and (2) specific treatment, including exposure to pressure and heat, and by gelatinization. Experimental
animals were six adult males of dark standard-type mink or “neovison vison” and blue fox or “vulpes lagopus”. The
digestibility was evaluated by the AIA indicator method with 0.5 silicate (celite 545) serving as an inert indicator.
Main components in the study feed were slaughter-house offal, Baltic herring, barley, and water. Ash content was
higher in specific than in traditional diet (p < 0.001). Crude protein content tended to be slightly higher in specific diet.
In blue fox and mink, digestibility of crude protein and fat were similar in traditional and specific diet (p > 0.005).
Digestibility of carbohydrates and organic matter was significantly (p < 0.01) better for specific than traditional diets.
Heat treatment including gelatinization can be recommended to use for better utilization of carbohydrate stuff in the diet.
KEY WORDS: Farmed furbearers, mink and blue fox, heat treatment, feed ingredients, fur farming, carbohydrate,
and digestive value.

HANNU T. KORHONEN & PAAVO NIEMELA,
Digestibility of Heat Treated Barley

Digestibility of carbohydrates
can be influenced by certain pre-
treatments during manufacturing
process. Particularly, heat
treatment with gelatinization is
expected to improve utilization
of carbohydrate components such
as starch (Ostergaard, 1998). This
mainly is a result of clear changes
in the structure of starch kernels
which become more accessible
for digestible enzymes, i.e.
gelatinization. The extent of changes
is known to depend on water
contents, temperature, and certain
conditions during process.

The aim of the present study was
to clarify effects of heat treatment
on digestibility of carbohydrates
in farmed juvenile blue fox (vulpes
lagopus) and mink (neovison vison)
during autumn period. This time of
the year is most crucial for proper
formation of body composition,
fattening, and furring process.
Two different heat treatments were
compared here: (1) traditional
treatment by extruder; and (2)
specific treatment including
exposure to pressure and heat,
and by gelatinization (Niemelä &
Korhonen, 1998). Gelatinization
means here boiling of starch.

MATERIALS AND METHODS
About the Experimental Animals.

The study was carried out at the MTT Fur
Farming Research Station, Kannus (63.54 oN,
23.54 oE), Finland, during the growing-furring
period (September 24th – October 3rd, 2013).
The use of experimental animals was evaluated
and approved by the Animal Care Committee
of MTT Agrifood Research, Finland.

Experimental animals were six juvenile
males of dark standard-type mink and blue
fox (blue colour type of the Arctic fox).
All animals were healthy and negative for
plasmocytosis. They were divided into
two different diet groups, as following: (1)
traditional treatment group; and (2) specific
treatment group, including exposure to

Picture 1:
Picture of Juvenile Blue Fox in a Wire-Netting Farm Cage

(Photo: Pekka Eskeli, 28/10/2013)

Picture 2:
Farmed Mink in Wire-Netting Cage.

Feed is Given on Top of the Cage
(Photo: Hannu T. Korhonen, 28/10/2013)

pressure and heat, and by gelatinization.
Gelatinization was made by heating
carbohydrates (starch) to ≤ 100oC (Niemelä &
Korhonen, 1998). The general health of the
animals was visually checked daily.

During the experiment, the animals were
housed singly in a wire-netting digestibility
cages in an experimental hall. Inside
temperature of the hall varied from +6 to
+10oC. The mink cages were 70 cm long x 30
cm wide x 38 cm high. Correspondingly, the
fox cages were 105 cm long x 115 cm wide x
70 cm high. Cages were lacking enrichments
like platform or gnawing object. Both in mink
and blue fox, experimental animals were

EDUCARE:
International Journal for Educational Studies, 7(1) August 2014

genetically equal, one male kit form a single
litter being taken into each of the groups.

About the Experimental Diets. The feed
was manufactured daily by the Fur Farming
Research Station, Kannus, Finland. The
amounts of experimental raw materials
were weighed with a balance, accuracy 10 g
(Neigungswage Bauart FO, Dayton Vaaka,
Finland; and Josef Florenz AG, Austria).
Experimental raw materials were mixed with
Stephan mixer (Stephan universal machine,
type UM 44). Details of the raw materials and
chemical compositions of the experimental
diets are given in tables 1 and 2.

Animals were fed once a day at 8-9 am
by hand. Daily feed portions were 350 g/
animal and 900 g/animal for mink and foxes,
respectively. Leftovers were collected the
next day. Feed portions were measured with
a Mettler SM 15 balance, accuracy ± 1 g.
Watering was automatic ad libitum. Their daily
routine treatments were conducted according
to standard farming procedures.

ANALYSES AND STATISTICS
Initially, animals were kept in digestibility

cages for four pre-test days. Actual
experimental period started after pre-test
period lasting five consecutive days (September
28th – October 2nd, 2013). Faeces of the animals
were collected daily and frozen. Urine was not
collected.

The digestibility was evaluated by the
AIA indicator method with 0.5 silicate (celite
545) serving as an inert indicator. Individual
feed and faeces samples were taken before
and during the collection period for detailed
analyses. The samples were analysed at the
laboratory of the Fur Farming Research
Station, Kannus (MTT), Finland. Standard
procedures were used for analyses of nitrogen
or kjeldahl and fat or HCL hydrolysis (Korhonen
et al., 2005). Carbohydrates were calculated
according to equation: 100- (ash + crude
protein + crude fat).

The apparent digestibility was determined
according to the following equation: Apparent
digestibility = a-b/a x 100, in which a = nutrient
in feed/indicator in feed; and b = nutrient
in faeces/indicator in faeces (Korhonen &
Niemelä, 2012). The Metabolizable Energy

(ME) content of the diets was calculated using
the factors 18.8 (protein), 38.9 (fat), and 17.2
(carbohydrates) per gram apparent digestibility
nutrient (Tauson, 1988).

Statistical analyses were performed by the
General Linear Models (GLM) procedure of
the Statistical Analysis System (SAS Institute
Inc., 1991) using Tukey’s Studentized range
(HSD) test and analysis of variance (Korhonen
& Niemelä, 2012).

RESULTS
Basic data and results can be found from

tables 1-3. Ingredients of the diets are given
in table 1. Main components in the feed were
slaughter-house offal, Baltic herring, barley
and water. This is a typical composition of
farm feed for caged foxes and mink.

Chemical composition of the diets are
shown in table 2. Ash content was higher in
specific than in traditional diet. Furthermore,
crude protein content tended to be slightly
higher in specific diet.

In blue fox and mink, digestibility of crude
protein and fat were similar in traditional and
specific diets (table 3). On the other hand,
digestibility of carbohydrates and organic
matter was significantly better for specific than
traditional diets. Digestibility of chemical
components was better in blue foxes than in
mink in general.

Solidity and general appearance of faces
was normal in each study group. Dry matter
content of faeces from traditional and specific
diets were in range of normal values. In
mink, the dry matter content for traditional
and specific diets were 28.39 ± 2.4 and 28.60
± 1.49%, respectively. In blue foxes, the
corresponding values were 33.71 ± 0.83 and
26.86 ± 1.04%, respectively.

DISCUSSION
The main ingredients in fur animal feed are

products of the fish and slaughter industries.
Typically, their amounts have varied by year
and season (Korhonen & Niemelä, 1998; and
Pölönen, 2000). Also carbohydrates are used in
the diet of farmed fur bearers. Carbohydrates
are cheap substitute nutritional wise for protein
and fat to meet the basal energy demands.
Therefore, they should be favored more in

HANNU T. KORHONEN & PAAVO NIEMELA,
Digestibility of Heat Treated Barley

the diet. They are typically also beneficial
for digestibility of farm feed. Therefore, use
of carbohydrates should be favored more in
future. However, further research is needed
before implementation in practice. This study
was part of this implementation project.

The decomposition of the feed substances
is done by means of alimentary enzymes.
Digestibility of carbohydrates demands
that enzymes have enough time to work
with the decompositions. Particularly, this
is problem for animals like the mink with
a short intestinal canal. Starch is the main
component of carbohydrates. Starch can
be made better digestible by “opening” its
structure. This can be done by heat treatment
where the material is exposed to pressure and
heat, and by gelatinization. Digestibility of
carbohydrates including starch may improve,
because of essential change of the structure

of starch kernels which becomes more easily
accessible for digestible enzymes (Ostergaard,
1998). The change of the structure is known as
gelatinization. This treatment was used for our
specific diet.

Comprehensive scientific interest has been
to improve diet and raw material digestibility
of feed in farmed fur animals. According to
literature, digestibility of raw barley in mink
typically is 45-52% and that of cooked barley
around 60%. Carbohydrate digestibility of
heated barley by extruder method, on the other
hand, is 57-60% and 65-73% in mink and blue
fox, respectively (Minkinkasvatus, 1967; Berg,
1986; and Niemelä & Korhonen, 1998).

In the present study, heat treatment also
included gelatinization of feed stuff. The
results showed that treatment significantly
increased digestibility of carbohydrates both
in the fox and mink. Furthermore, it was also

Table 1:
The Composition of Experimental Diets

Ingredient (%) Traditional Specific
Slaughter-house offal
Baltic herring
Barley
Water
Celite 545

26.09
36.52
15.65
20.20
0.50

26.54
37.15
15.92
18.83
0.50

Table 2:
Chemical Composition of Diets

Variable Traditional Specific
Dry Matter (DM), %
In DM, %: Ash
Crude protein
Crude fat
Crude carbohydrate

33.31
9.93
28.88
20.43
40.77

33.97
7.82
27.63
20.05
44.49

Table 3:
Digestibility (%) of Traditional and Specific Diet Components in Blue Fox and Mink

Variable
Blue Fox Mink

Traditional Specific Traditional Specific
Crude protein

Crude fat

Crude carbohydrate

Organic matter

79.97
(1.64)
91.17
(1.74)
51.75
(5.14)
66.01
(2.93)

79.03
(1.01)
89.87
(1.03)

71.91**
(1.79)

76.81 **
(1.14)

73.92
(3.46)
77.85
(5.82)
43.51
(5.83)
64.78
(4.40)

77.17
(2.85)
80.10
(2.04)

69.55**
(2.18)

75.27**
(2.06)

Significant difference: **p < 0.001. Standard deviations are given in parenthesis.

EDUCARE:
International Journal for Educational Studies, 7(1) August 2014

found that digestibility of organic matter is
increased by combination of heat treatment
and gelatinization.

General concept is that digestibility of feed
stuff is better in farmed foxes than in mink
(Niemelä & Korhonen, 1998; and Korhonen
& Niemelä, 2012). The mink typically have
a short digestibility tract thus food is passing
trough very fast, i.e. in 4-5 hours (Sibbald et
al., 1962; Jorgensen ed., 1985; and Korhonen,
Sepponen & Eskeli, 2013). This also impairs
digestibility of food in the digestive tract.
Furthermore, foxes typically are known
to utilize more versatile food than mink.
The present results confirm this concept.
Digestibility of carbohydrates, protein, and fat
tended to be better for the blue fox than for the
mink. Most pronounced this tendency was for
carbohydrates and organic matter.

CONCLUSION 1

The results of the present study are
promising. They encourage us to continue
in clarifying the suitability of various
carbohydrate stuffs for farmed foxes and mink.
In addition to barley also oat, for example,
can be considered as a potential carbohydrate
resource in future. The use of carbohydrates
as a part of the feed for farmed furbearers is
advantageous, while production costs can be
declined by not using so much fat and protein.

The present results are also promising.
They showed that heat treatment of barley
with gelatinization is effective to increase
digestibility of carbohydrates in farmed mink
and fox diets. Digestibility of barley is better in
farmed foxes compared to mink.

References

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1Acknowledgements: This study was financially supported by
MTT Agrifood Research, Finland. The staffs of MTT Research
Station are kindly acknowledged for their valuable help in
carrying out this digestibility experiment. Special thanks to
Pekka Toikkanen, Terho Lindqvist, Jaakko Huuki, Aimo Joki-
Huuki, and Pekka Eskeli for good co-operation and technical
help. Many thanks are also extended to Juhani Sepponen for
statistical analyses. However, all content and interpretation in the
article are solely responsibilty to the authors academically.

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