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OCR for page 7
Mink:
Recommendect
Dietary
Allowances
ENERGY
Maintenance
Hodson and Smith (1945) found that mink require 273 kcal of
gross energy per kilogram of body weight daily for mainte-
nance. More recently, Perel'dik et al. (1972' have listed
calculated daily maintenance requirements on a monthly
basis, with allowances for variations in environmental
temperatures and in body weights. These latter values, rang-
ing from 191 kcal ME per animal (nonpregnant female) in
April-May to 237 kcal ME per animal in March to 334 kcal
ME per animal in October, agree quite closely with practical
observations of Rimeslatten in Norway (1964~.
Farrell and Wood (1968) reported that female pastel mink
used from 202 to 258 kcal of DE (estimated as 182-232 kcal of
ME) per kilogram per day for maintenance in the months
September to November (in a location of moderate climate).
The range resulted from different activity levels attendant
upon housing in very small or conventional farm cages.
Perel'dik et al. (1972) have summarized daily maintenance re-
quirements as 200 kcal of ME per kilogram of body weight
throughout the year.
More recently, on the basis of regression analysis of the
energy gain:energy intake response in growing male mink,
Harper et al. (1978) have reported the daily ME requirement
for maintenance as 147.8 + 6.06 kcal/kg MBS. From this they
have calculated the daily requirement for E as 203 kcal/kg
MBS. (In their work, Harper et al. (1978) used BWkg0 73-
rather than BWkg0 75 for the calculation of MBS). These
authors also recalculated the data of Hodson and Smith
(1945), arriving at the value of 260 kcal E/kg MBS/day.
Conversion of the value of Harper et al. (1978) to the actual
body weight basis yields daily maintenance requirements
ranging from 176 kcal ME/kg BW for an animal of 500 g down
to 124 kcal ME/kg BW for an animal weighing 2,000 g.
Chwalibog et al. (1979) also used regression analysis of the
results of energy balance experiments to estimate the main-
tenance requirements of adult male mink; they found a
marked effect of environmental temperature and of dietary
protein level on the retention of energy by the animals. In the
thermoneutral zone (20°C), the maintenance requirement
was found to be 126 keel ME/kg MBS. (In addition to using
MBS as a basis, these workers expressed energy as kilojoules;
conversions to kilocalories have been made for the present
discussion.) For comparison with the values of Harper et al.
(1978), this maintenance requirement corresponds to values
for mink ranging from 500 to 2,000 g BW of 150 to 106 kcal
ME/k~ BW. The lower values of Chwalibog et al. may be
related to the strict temperature control in their experiments
or to the use of older animals or to both. Glem-Hansen and
Chwalibog (1980) found that the requirement for ME in-
creased by 3.7 kcal/MBS per degree Celsius per day.
In the light of the diverse experimental methods and cir-
cumstances involved in the various studies described above
and the ranges of results reported, the establishment of a firm
recommendation for maintenance energy requirements is im-
possible. However, giving extra weight to the results of the
more recent careful studies, a daily intake of 140 kcal ME/kg
BW for the maintenance of mature mink is suggested as a ten-
tative guideline.
Limited experimental data are available on the requirements
of energy by mink during pregnancy, largely as a consequence
of the obvious difficulties of conducting and assessing such
studies. One common suggestion, on the basis of limited North
American studies (Travis and Schaible, 1961; Evans, 1964a),
has been that adequate performance will be achieved by pro-
viding diets of energy content comparable to that of diets used
for optimal early growth of kits. Recommendations on a more
fundamental basis have been made by European investiga-
tors. Perel'dik et al. (1972), after reviewing Scandinavian pro-
duction records and recommendations, as well as the recom-
mendations for other forbearing species, suggested that the
needs of the pregnant female mink will be met by increasing
the maintenance energy allowance by 15 percent during the
last month of pregnancy. Thus, a level of 230 kcal of ME per
kilogram of body weight per day was recommended by these
authors. This level, being based on maintenance recommen-
dations of Perel'dik et al. (1972), which are much higher than
7
OCR for page 8
8 Nutrient Requirements of Mink and Foxes
those proposed in the preceding section, appears rather high.
In the absence of any more fundamentally derived estimates,
however, there is no justification for proposing an intake of
less than 200 kcal ME per kilogram of body weight during the
last month of pregnancy.
Lactation and Growth
The growth of kits during the first 3 weeks of life depends upon
energy supplied by the dam's milk, and, to a declining extent,
this demand continues until weaning. Consequently, the lac-
tating female must receive additional energy for milk produc-
tion, the amount required increasing with the increasing
demands of the developing kits for energy and nutrients.
Based on calculations from production data on Russian and
Scandinavian farms, Pereltdik et al. (1972) have presented
recommendations for increased energy supplies to lactating
females on the basis of the following scale of daily levels of ME
per kit during successive 10-day periods of the lactation: 5, 20,
50, 70-90, and 110-150 kcal. Multiple regression studies in
Denmark (N. Glem-lIansen, National Institute of Animal
Science, Hilleroed, Denmark, personal communication,
1978) have provided information on the additional re-
quirements of the lactating female for ME, above the
maintenance requirement, to provide for weight increase in
her kits. A mean value of 2.6 kcal ME per gram of kit weight
increase was derived. Although this mean value can serve as a
guide, it should not be applied indiscriminately. In practice,
the increments required will be achieved by increased con-
sumption of the high-energy diet by the female.
The weaned kit must obtain its entire energy supply from
the growth diet; the requirements will increase rapidly with
the rapid growth, especially during the early weeks. The kit
will be able to meet these requirements by increasing the con-
sumption of the diet, provided the energy content of the diet is
high enough. Because of the rapidly changing kit weights, re-
quirements are more commonly expressed as averages per day
rather than on the weight basis (per kilogram). Rimeslatten
(1964) and, later, Perel'dik et al. (1972), working from data
from numerous Scandinavian and Russian practical studies,
calculated average combined figures for male and female kits
for each month of the growing period. These figures also in-
cluded an increase of 10 percent to cover practical en-
vironmental conditions and were as follows:
Early Period
Late June
July
August
ME
kcal/day
200
250
310
* Includes furring as well as growth.
Late Period*
September
October
November
December
ME
kcal/day
340
330
300
280
These authors noted that the male required 33 percent more
energy than the female. These different requirements will
usually be met by differential intakes of a single diet of ade-
quate energy concentration.
Practical recommendations for energy supplies for growing
mink have most commonly been made in terms of energy per
kilogram (or per 100 g or per gram) of diet.
Allen et al. (1964) reported that a minimum of 4.9 kcal of E
or 3.7 kcal of apparent DE per gram of feed dry matter (DM)
would be required for optimal early growth of male mink kits
and that 4.5 kcal of E per gram DM (3.4 kcal DE) would suf-
fice for female kits. Later recommendations from the same
laboratory, based on further studies with larger genetic strains
(Evans, 1964a; Evans and Travis, 1967), repeated and con-
firmed over several years using different dietary ingredients
and at different locations, were 5.3 kcal E per gram DM of
diet for males and 5.1 kcal E per gram DM of diet for females.
This recommendation for males was supported by Wood and
Farrell (1965~.
Using the previously cited average figure of 77 percent for
converting E to ME values, the above E recommendations of
5,300 and 5,100 kcal become, respectively, 4,080 and 3,930
kcal ME per kilogram DM of diet, values adopted for use here.
Energy Density and Its Implications
The concept of energy density of diets is of both theoretical
and practical importance. It deals with the concentration of
energy in the diet. A diet of high-energy density (often referred
to simply as a "high-energy diet") provides more kilocalories
per gram than does a diet of low-energy density ("low-energy
dieted. In the recommendations cited in the preceding section,
the diet of 4,080 kcal ME per kilogram is of greater energy
density than the one of 3,930 kcal ME per kilogram. Diets used
experimentally and practically, however, have ranged from
much higher to much lower energy densities than these. For
example, records from 45 Danish central feed-processing units
during 1969 and 1970 showed variations in energy density
from 3,400 to 3,900 kcal ME per kilogram of DM (Nielsen,
1973~. Similarly, Swedish practical mink diets have ranged
from 3,500 to 4,SOO kcal ME per kilogram of dry matter iE.
Alden, Department of Animal Husbandry, Agricultural Col-
lege of Sweden, personal communication, 1978~.
It is of interests that some Scandinavian investigators are
convinced that the optimal energy densities of diets vary
depending upon the DM contents of the diets as fed, as well as
upon the nature of the diet ingredients. For instance, success
with the feeding of dry diet forms is believed to be contingent
upon a relatively high energy density in the diets (G. Joergen-
sen, National Institute of Animal Science, Hilleroed, Den-
mark, personal communication, 1978~.
Since the mink generally eats to satisfy energy demands and
will curtail intake when these demands are met, the density of
energy in a diet will be a main factor governing feed intake,
assuming that palatability is ensured. Thus, an animal will re-
quire and will consume less of a high-energy density all-et and
more of one of low-energy density. It has been noted that feed
consumption varies inversely with energy density over a con-
siderable range of density values (Evans, 1963~. Calculations
of energy density of diets in over experiments, in which
published variable feed intakes were either not accounted for
or not commented on, strongly suggest that the energy den-
sities were probably important causative factors of the dif-
ferential intakes.
OCR for page 9
Nutrient Requirements of Mink and Foxes 9
This relationship between energy density and consumption
of diets is the major argument in favor of the principle of ex-
pressing nutrient recommendations on a basis that relates
them to the energy recommendations.
It should be emphasized that factors such as palatability
and digestibility of the feed and the feeding technique (i.e., ad
libitum or restricted feeding) will have marked effects on the
level of feed consumption.
The capacity and the digestive capability of the gastrointes-
tinal tract of the mink are limited, and it may be physically
impossible for an animal to consume sufficient amounts of a
low-energy diet to satisfy energy demands; this will be par-
ticularly true in periods of high-energy requirements such as
lactation and early kit growth. It is also important that the
diets fed during these periods be of high palatability and
digestibility. Conversely, too great a concentration of energy
in the diet may have adverse effects, primarily by reducing
total diet intake and perhaps causing deficiencies of protein or
other essential nutrients. A considerable margin exists,
however, in both directions. Within these limits, the decision
as to whether the energy density of the diet will be selected to
coincide with the density required to produce optimal growth
or at levels above or below this optimum may well depend
upon the relative costs of feed ingredients.
FAT
Fat (lipid), as the most concentrated supplier of energy to
diets, is the (actor that plays the greatest role in varying the
energy density of those diets. Consequently, high-energy diets
are, of necessity, diets that are relatively high in fat. The fat
may be supplied to varying degrees as a constituent of com-
monly used feed ingredients. Thus, most animal and fish prod-
ucts and by-products are substantial, but variable, con-
tributors to the fat content of the diet. On the other hand,
many of the ingredients of cereal or other products of plant
origin are usually low in fat. In many instances the addition of
rendered fats or oils (tallow, lard, fish oils, vegetable oils, etc.)
will be necessary to achieve desired energy levels in the diets;
the need for and the extent of this supplementation will de-
pend upon both the other diet components and the life-stage of
the animals to receive the diet.
The need for adding fat to certain diets was reported by
Belcher et al. (1958) for growing mink and by Friend and
Crampton (1961a) for reproduction.
The inclusion of certain high-fat ingredients (particularly
certain fish products) or the addition of fat supplements to
mink diets was, for many years, considered undesirable based
on reports of untoward effects; stimulation of yellow fat dis-
ease or the causation of wet-belly disease were two major criti-
cisms of these ingredients. There is clear evidence that yellow
fat resulted from the poor quality, i.e., the rancidity, of the fat
in the ingredients. Care in the selection of these ingredients
and the correct use of antioxidants in the storage of ingredients
and in preparation of the mixed diets can eliminate this prob-
lem. The case concerning wet-belly is less clear, and contra-
dictory reports have appeared, some suggesting possible asso-
ciation of wet-belly with high fat levels (Leoschke, 1959a;
Evans et al., 1961) and others reporting little or no problem
with certain strains of animals receiving high levels of fat in
the diet (Stout et al., 1964, 1965; Evans, 1964b, 1967a).
Another problem once attributed to high fat intakes was
poor color in dark pelts (Stout et al., 1963~; however, later
reports (Stout et al., 1965) covering 1,500 mink indicated no
direct causal relationship between diet fat level and fur color.
There is general agreement that the percent digestibility of
most fats is quite high (with the exception of certain very hard
tallows) and that the separated fats may frequently be di-
gested to a higher degree than those associated with certain of-
fals and other ingredients (Leoschke, l959b; Lehman, 1959;
Evans, 1967b; N. Glem-Hansen, National Institute of Animal
Science, Hilleroed, Denmark, personal communication, 1978~.
The digestibilities of the fat of most mixed diets will range be-
tween 80 and 90 percent (rarely higher) with a mean of 85
percent or more. Comprehensive Danish investigation Uoer-
gensen and Glem-Hansen, 1973) showed that 85 percent of the
variation in the digestibility of fats by mink is due to the con-
tent of stearic acid (the saturated 18-carbon fatty acid). These
workers presented a formula by which the digestibility of a fat
can be calculated if the content of stearic acid is known.
The levels of fat reported to have been used satisfactorily in
mink diets range up to 35 or 40 percent of DM. The total
dietary fat required to achieve, for example, an E content of
5.3 kcal of E per gram of DM of diet will usually be approx-
imately 25 percent of the DM, the level required for optimal
metabolic performance and utilization, depending, of course,
on the digestibility of the particular fat.
Perel'dik et al. (1972) and Leoschke (1980) have made
recommendations on two bases-as grams of digestible fat per
day per kilogram body weight or as percent of the total ME.
Leoschke's recommendations on the latter basis are for fat to
supply the following percentages of the total ME of the diet:
for growth 44-53 percent, for fur development (including late
growth) 42-47 percent, for pregnancy 34-37 percent, and for
lactation 47-50 percent.
In addition to its contributions of energy, dietary fat must
also provide the required amounts of essential fatty acids,
notably linoleic acid. Unfortunately, only limited data on
these requirements are available. From a review of published
reports Perel'dik et al. (1972) concluded that the minimum
supply of essential fatty acids necessary to maintain healthy
adult animals was 0.5 percent of the diet DM; for pregnant
and lactating females and young growing mink 1.5 percent of
the diet DM was recommended. (If one assumes a typical diet
providing 4,000 kcal ME/kg DM, this latter recommendation
involves 60 kcal ME, or 1.5 percent of total ME, from linoleic
acid.j More recently, N. Glem-Hansen (National Institute of
Animal Science, Hilleroed, Denmark, personal communica-
tion, 1978), in investigations of the requirement of the lac-
tating female as judged by growth of the nursing kits, found a
higher requirement of linoleic acid 5 percent of the ME in
the diet-for optimal kit growth from birth to weaning.
CARBOHYDRATE S
No critical studies have been made on the carbohydrate re-
quirements of mink; indeed, there have been no indications
OCR for page 10
10 Nutrient Requirements of Mink and Foxes
that there is an actual requirement. The primary (and perhaps
the sole) function of carbohydrates in mink diets is, as in diets
of other species, to supply energy; there are no reports of other
special functions for any particular forms of carbohydrate.
Widely different levels of carbohydrates have been used in
mink diets, the higher levels usually occurring in experimental
diets. For example, Tove et al. (1949) fed a purified diet con-
taining 60 percent sucrose. In most practical diets and in many
experimental diets the carbohydrate content often exists
largely as a filler to provide the remainder of the energy after
certain specific protein and fat levels have been selected.
Thus, the levels of carbohydrate in such diets vary inversely
with the levels of protein and energy. Recommendations for
satisfactory levels in diets for various life stages reflect this
fact.
Pereltdik et al. (1972), citing the Scandinavian work of
Rimeslitten (19S9a), Nhman (1961), and loergensen (1967),
recommended that carbohydrates supply not less than 10 per-
cent and not more than 30 percent of ME; the best results will
be obtained, it was suggested, when 15 to 25 percent of the
ME is supplied by carbohydrates. Leoschke's recommenda-
tions (1980) cover the same general span, but they specify the
following ranges, as percent of ME: for growth and for fur
development, 15-30; for pregnancy and lactation, 10-20.
Starch is the major carbohydrate of ingredients used in
mink diets; in most of these sources the digestibility (and hence
the ME contribution) of the starch can be significantly in-
creased by cooking, "popping," or similar heat treatment
o
(Ahman, 1959; Evans, 1964c; Leoschke, 1965; Glem-Hansen
and Joergensen, 1978~. Glem-Hansen et al. (1977), working in
Denmark, have shown that a reasonably accurate estimate of
the digestibility of a carbohydrate by mink can be made by a
calculation based on the results of analyses of the content of
or-linked glucose in the feed sample before and after auto-
claving.
PRO TE IN
Animals do not require protein of itself, but actually require
the individual amino acids present in the feedstuff protein. It
follows, then, that the designation of specific protein re-
quirements for the mink is difficult. The animal's protein re-
quirement will be related to the protein quality in a given
feedstuff.
Amino acid balance and amino acid availability are the two
primary factors providing the bases for defining a protein
feedstuff as high or low quality. Meat is illustrative of a high-
quality protein feedstuff, as it possesses a protein content that
(1) is highly digestible by animals and (2) contains an amino
acid pattern similar to the actual amino acid requirements of
the animal. Chicken feet are illustrative of a low-quality pro-
tein feedstuff, because (1) the protein is relatively indigestible
(only 52 percent digestibility rating for mink ~Leoschke,
1959b]) and (2) the amino acid balance is inconsistent with the
actual amino acid needs of the mink as a consequence of
relatively low levels of certain amino acids such as tryp-
tophan.
Carefully processed fish meal products have good digestibil
ity ratings for mink and a good amino acid pattern. However,
overheated fish meal products are unable to provide the mink
with a pattern of digestible amino acids consistent with the ac-
tual needs of the animal. Excessive heating of fish products in
the dehydration procedures can result in the destruction of the
amino acid lysine and the bonding of the amino acid arginine
in an indigestible form (Allison, 1949~. Tryptophan and the
sulfur amino acids, cystine and methionine, are especially sen-
sitive to destruction during the dehydration of protein
foodstuffs (Varnish and Carpenter, 1975~.
The protein quality of a feedstuff is related to the amino
acid pattern and availability of the amino acids present in the
proteins to the digestive process of the animal. It is apparent
that protein quality is of major importance in the assessment
of the protein requirements of the mink inasmuch as the mink
have (1) a limited digestive capability due to a relatively short
time of feed passage (average passage time 142 minutes) (Sib-
bald et al., 1962) and (2) an extra requirement for arginine
and the sulfur amino acids during the critical fur-development
months (Leoschke and Elvehjem, 1959a; Glem-Hansen,
1980a,b,c).
Protein quality and dietary energy density account, in part,
for the great variation in experimental data on the protein re-
quirements of the mink. Feed intake of the mink is primarily
determined by the taste appeal and caloric density of the diet.
Considering the critical role of dietary energy densi.ty in the
determination of mink feed intake, it is logical to relate the
protein requirements of the mink to the energy content of the
diet rather than to list them simply as a percentage of protein
in the diet.
Lower levels of protein than those indicated in Table 1 may
yield quite satisfactory performance if the protein quality is
superior and the fat:carbohydrate ratio is kept high. This has
been shown repeatedly when feeding complete dry diets. On
the other hand, when the diet contains largely poor-quality
sources of protein, it may be advisable to increase the mini-
mum recommendation with a safety margin.
It is important to emphasize the fact that the data presented
in the tables represent the minimum protein requirement of
mink during different phases of the life cycle. Producers may
wish to use higher protein levels to provide a margin of safety.
Producers are advised to be aware of problems likely to be
associated with borderline protein nutrition, including re-
tarded growth, suboptimal fur development, and poor repro-
duction-lactation performance of the mink.
Gestation
Experimental data from mink fed diets that contained 40, 45,
and 50 percent digestible protein indicated no significant dif-
ference in reproductive performance (Petersen, 1957a). Nor-
wegian studies cited by Glem-Hansen (1974) have shown that
diets varying from 29 to 64 percent of the ME from digestible
protein (for calculations see Table 9) did not significantly in-
fluence the reproductive performance of the mink. Studies
covering a slightly wider range of protein content (Glem-
Hansen, 1974) have shown a tendency toward suboptimal re-
productive performance with dietary protein levels both very
high (70 percent of ME from digestible protein) and very low
OCR for page 11
Nutrient Requirements of Mink and Foxes 11
(25 percent of ME from digestible protein). Results of the
Scandinavian investigations indicate a minimum protein re-
quirement of 35 percent of the ME from digestible protein
during the critical gestation period.
Lactation
Investigations by Lehman (1967) and Joergensen and Glem-
Hansen (1970, 1972) have shown that calories from digestible
protein during lactation should be higher than 40 percent of
the total ME in the diet. Glem-Hansen (1979) studied the lac-
tation performance of females and early growth of mink kits in
the period from birth to 42 days of age. Prior to whelping, all
experimental females received the identical farm feed. The in-
vestigation involved protein levels ranging from 21 to 54 per-
cent of the ME from protein. The growth performance of the
mink kits receiving 42 percent ME from digestible protein was
superior to that of kits on the 34 percent level and lower levels
of protein.
Early Growth /~9-13 Weeks)
The protein requirement of mink during the growth period
from about 9 to 28 weeks of age has been studied by a number
of investigators including Sinclair et al. (1962), Allen et al.
(1964), Adair et al. (1966), Joergensen and Glem-Hansen
(1970, 1972), and Skrede (1975, 1978~. These experiments in-
dicate that the protein requirement for this period is about
35-45 percent of ME from digestible protein depending on
quality. Experiments in which the growth season was divided
into periods showed that the protein requirement from birth
to 16 weeks of age is higher than during the period from 16 to
28 weeks of age Uoergensen and Glem-Hansen, 1970, 1972~.
Studies by Glem-Hansen (1980a' indicate that the digestible
protein requirement during the period of early growth from 9
to 13 weeks of age is approximately 35-40 percent of the ME.
It is important to note that the protein recommendations
made in the preceding paragraphs apply to male kits. A num-
ber of studies indicate that the actual protein requirement for
female kits will be considerably lower. In studies conducted
by Glem-Hansen (1980b), a level of 42 percent ME from
digestible protein was required for optimal growth of male
kits during the period from birth to 42 days of age. However,
these same investigations indicate that a level of 34 percent
ME from digestible protein will provide optimal weight gains
for female kits during the period from birth to 6 weeks.
Growth studies by Leoschke (Valparaiso University, personal
communication, 1978) with mink kits 7 to 10 weeks old in-
dicated significantly lower protein requirements for female
kits relative to male kits.
Late Growth (13-30 WeeksJ
Howell and Gunn (19SS) considered 32 percent crude protein
to be sufficient for maximum growth of mink, while Stout et
al. (1963) found that a level of 25 percent crude protein during
the growth period was necessary for maximum growth of
body and fur. The protein requirement of mink during the late
growth period has been studied by a number of other investi
gators including Sinclair et al. (1962), Allen et al. (1964),
Adair et al. (1966), Joergensen and Glem-Hansen (197O,
1972), Skrede (1975, 1978), and Glem-Hansen (1980b). These
studies indicate that the digestible protein requirement for the
late growth period is approximately 30 percent of the ME.
Fur Development (16-30 Weeks)
Studies by Glem-Hansen (1980b) indicate that, although a
protein level of 24 percent of ME from digestible protein is
satisfactory for maximum growth of the mink in the period
from 16 to 30 weeks, this protein level does not necessarily en-
sure maximal fur development. Glem-Hansen recommends a
diet containing 30-35 percent of ME from digestible protein
during the critical fur development phase.
Amino Acid Supplementation
A number of studies have been conducted on the value of sup-
plementing practical ranch diets with specific amino acids.
Some of the earliest studies on amino acid supplementation of
mink diets were conducted at Oregon State University (Watt,
1952~. These studies indicated that supplementation of high-
fish diets with 0.05 percent methionine (dry basis) improved
the growth and fur quality of the mink. Studies at the Univer-
sity of Utrecht by Hoogerbrugge (1968) showed the value of
lysine and methionine supplementation of dry diet formula-
tions. Dehydration procedures required for the production of
fish meals and poultry by-product meals may result in lysine
destruction, hence the benefits of lysine supplementation for
dry diet and pellet formulations.
Heat Processing of Protein Feedstuffs
Heat processing of mink feedstuffs may increase or decrease
the nutritional value of these products for mink. Cooking of
eggs is an absolute requirement for their use in practical mink
rations. lIeating of eggs for at least 5 minutes at 91°C (196°F)
denatures avidin, a protein that binds the vitamin biotin in an
indigestible linkage. Heating of eggs also denatures egg pro-
teins that bind iron in a structure unavailable to the digestive
processes of the mink (W. L. Leoschke, Valparaiso University,
personal communication, 1978~. Heat processing of raw soy-
bean oil meal is essential for the denaturation of a trypsin in-
hibitor (trypsin is a protein-digesting enzyme). Conversely,
heat processing of mink feedstuffs such as fish and poultry by-
products (heads, entrails, and feet) may actually lower their
nutritional value. Studies have shown that certain amino acids
including lysine and arginine are heat-labile (Allison, 1949~. It
is important to note that arginine is of critical importance for
the fur development of the mink (Leoschke and Elvehjem,
1959a).
FAT-SOLUBLE VITAMINS
Vitamin A (Retinol)
A growing mink needs between 100 and 400 international
units (IU) of vitamin A per kilogram of body weight daily (1
OCR for page 12
12 Nutrient Requirements of Mink and Foxes
IU = 0.3 ,ug retinal). At the 100-IU level, the amount stored in
the liver is slight; at the 400-IU level, the amount stored is sig-
nificantly larger (Abernathy, 1960~. The amount suggested to
meet the requirement is about 200 IU per kilogram of body
weight. Because a rapidly growing mink kit needs between
275 and 350 kcal of ME per kilogram of body weight per day,
a requirement of 200 IU per kilogram of body weight will be
met by a diet providing 57 to 72 IU of vitamin A per 100 kcal
of ME.
Experiments conducted by Warner et al. (1963), in which
plasma and liver vitamin A levels were measured after feeding
carotene or alfalfa meal, showed that mink are inefficient in
converting carotene to vitamin A. This work demonstrates
that alfalfa meal and probably other plant sources of carotene
are poorly utilized by mink. In the absence of evidence to the
contrary, the carotene content of the diet should be disre-
garded in supplying the vitamin A requirement for mink.
Signs of Deficiency Vitamin A deficiency has been produced
and described for mink (Helgebostad, 1955; Stowe et al.,
1959; Abernathy, 1960~. When a purified diet devoid of vita-
min A is fed, animals fail to grow normally. They develop
night blindness and lack coordination, particularly in the rear
quarters. Their eyes are affected, with the lenses becoming
opaque and the conjunctival encrusted. Metaplasia of epithe-
lial tissues and fatty infiltration of the liver occur. The skull
does not enlarge normally; as a result, the cerebellum is com-
pressed and herniates into the foremen magnum. Damage to
the cerebellum results in muscular incoordination.
Signs of Excess Helgebostad (1955) investigated effects of
high levels of vitamin A on kits and adults. Mink tolerated 40
IU of vitamin A per gram of body weight without disturbance
over periods of 3 to 4 months. Fully grown animals could
tolerate from 200 to 300 IU per gram of body weight daily for
from 6 to 8 weeks, but young animals were affected in a
shorter time. Signs of excess were anorexia, bone change with
exostosis, decalcification and spontaneous fractures, losses of
fur, exophthalmia, and hyperesthesia of the skin.
Adair et al. (1977) and Travis (1977) conducted a coopera-
tive study in which levels of 1,000 to 160,000 IU of vitamin A
per mink per day (approximately 1-160 IU per gram of body
weight per day) were fed during the reproductive cycle start-
ing in January. Reproduction was normal (4.7-4.9 kits per
female on experiment) in the mink receiving from 1,000 to
10,000 IU per mink per day, slightly reduced (3.6-3.7 kits per
female on experiment) in the mink receiving from 20,000 to
40,000, and severely reduced (0.86 kits per female on experi-
mentJ in the mink receiving 160,000 IU of vitamin A per mink
per day. Reduction in performance in the latter group was due
to failure of females to whelp, to smaller litter size, and poorer
kit survival.
Friend and Crampton (1961b) observed that reproductive
performance in mink was reduced when whale liver in
breeder diets was increased from 5 to 10 percent. They postu-
lated a hypervitaminosis A toxicity. Assuming that these mink
consumed 15 g per day of whale liver, containing 4,400 IU of
vitamin A per gram, they would have received 66,000 IU of
vitamin A per day from the whale liver alone.
Vitamin D
Bassett et al. (1951) suggested that a diet of natural foodstuffs
without a vitamin D supplement is probably adequate for
v v . A A daily supplement of 200
IU of vitamin D per kg of body weight does not prevent ra-
chitic changes when calcium or phosphorus is deficient nor
does it improve physiological responses on adequate mineral
levels. Danish experiments with 10, 25, and 40 IU vitamin D
per gram of dry matter per day from July to pelting did not
show any significant differences in pelt characteristics (Hille-
man, 1978~.
growing mink exposed to sunlight.
Signs of Deficiency Mink, when they are fed a diet that is
low in vitamin D with an abnormally low calcium-to-phos-
phorus ratio, develop rickets (Smith and Barnes, 1941; Bassett
et al., 1951~. Also, when the diet is deficient in calcium or
phosphorus, bone development is abnormal.
Signs of Excess Large doses of vitamin D over a period of
time can produce a toxic effect, particularly when the diets are
high in calcium. The clinical signs are loss of appetite, nausea,
loss of weight, and digestive disorders. Hypervitaminosis can
take place in 2 or 3 weeks when the daily dose in the food is
10,000 IU or more per kilogram of body weight (Pereltdik et
al., 1972~.
Vitamin E
Vitamin E is defined in terms of the activity of one of its forms
(1 IU of vitamin E = the vitamin E activity of 1 mg of syn-
thetic, racemic o`-tocopheryl acetate). Vitamin E acts both as
a vitamin and as an antioxidant Vitamin E is spared by other
antioxidants in the feed or added to the feed. Conversely pro-
oxidants such as iron or copper cause its destruction. Thus, the
requirements for vitamin E cannot be stated without consider-
ation of the specific conditions of the diet fed.
Requirements of o`-tocopherol were determined by Stowe
and Whitehair (1963) to be about 25 mg per kilogram of a
purified diet with molecularly distilled lard as a source of fat.
This is equivalent to 0.66 mg per 100 kcal of ME.
The exact interrelationship between vitamin E and the min-
eral selenium is unknown and may vary between species. A
level of 0.1 ppm of selenium as sodium selenite added to a vita-
min E-deficient diet of mink prevented all lesions except
minor accumulations of amorphous nonacidfast material at
the adipose interstices (Stowe and Whitehair, 1963~. Mink fed
marine products are generally supplied adequate levels of sele-
nium in the diet (Kangas, 1974~.
When mink diets contain rancid fats or are high in polyun-
saturated fatty acids (PUFA), the animals are subject to
yellow fat disease. * Mink receiving such diets require an ade-
quate supply of vitamin E, especially during growth (Lalor et
al., 1951; Mason and Hartsough, 1951; Ender and Helge
*This disease has been given various names, including yellow fat dis-
ease (McDermid and Ott, 1947), nonsuppurative panniculitis (Quor-
trup et al., 1948), Weber Christian disease (Quortrup et al., 1948),
and steatitis (Hartsough and Gorham, 1949~.
OCR for page 13
Nutrient Requirements of Mink and Foxes 13
bostad, 1975~. The best information available is that of Harris
and Embree (1963), who proposed a dietary a-tocopherol:
PUFA ratio of 0.6 (milligrams:grams) for humans as a mini-
mum to protect against PUFA oxidation. For information on
the effects of antioxidants on the incidence of yellow fat
disease, the reader is referred to the section on antioxidants.
Signs of Deficiency Signs of an uncomplicated deficiency
produced using a purified diet include sudden death due to
minor stress, dystrophic lesions of the intercostal and myocar-
dial muscles, and hepatic fatty infiltration (Stowe and White-
hair, 1963~. The most significant clinical sign was increased
erythrocyte fragility (Stowe and Whitehair, 1963~. Similar le-
sions have been reported in mink on practical ranch diets by
Nordstoga (1969~.
Kits with yellow fat disease are first affected shortly after
weaning, and losses may continue until pelting time. The dis-
ease usually appears suddenly. The kits may refuse the night
feeding and be dead in the morning. Other affected kits may
leave their feed and show a peculiar, unsteady hop. The im-
paired gait may become gradually worse until the animals are
unable to move. They become comatose and remain so until
they die. In a typical outbreak, without early treatment, nu-
merous losses may occur. Vitamin E supplementation is usu-
ally effective.
At pelting time, nearly all the kits that survive on vitamin
E-deficient diets show yellow discoloration of the fat. Blood
appears in their urine. An examination of the blood suggests
that a general normocytic, normochromic anemia, which
does not respond to administration of iron, is a further sign of
yellow fat disease (Gorham, 1963~.
"Cotton fur" may accompany this condition if rancid fat is
fed during the period of active fur formation (Stout et al.,
1960a) (Figures 6 and 7~. Also, the frequency of "red hips"
(poor-quality fur or unprime areas on hips) increases (G. Joer-
gensen, National Institute of Animal Science, Hilleroed, Den-
mark, personal communication, 1978~.
Vitamin K
Little work has been done on vitamin K levels in mink diets,
and a deficiency of vitamin K in practical diets appears un-
likely. Travis et al. (1961) found that adding vitamin K to a
basal semipurified diet low in the vitamin (0.037 ,ug per 100
kcal ME) produced no change in blood prothrombin time.
WATER-SOLUBLE VITAMINS
Ascorbic Acid (Vitamin CJ
No requirement for vitamin C for growth or reproduction has
been demonstrated on diets adequate in other nutrients (Bas-
sett et al., 1948; Petersen, 1957b).
Biotin
Biotin deficiencies have been produced by feeding purified
diets to growing kits (Travis et al., 1968~. The requirement
was shown to be less than 0.003 mg per 100 kcal ME (Schimel-
man et al., 1969~. This was the lowest experimental level in-
vestigated. Deficiencies of biotin are not normally en-
countered on conventional mink diets. However, they can be
induced by inclusion of turkey breeder offal or eggs in the diet
because of the presence of avidin (Stout et al., 1966; Wehr et
al., 1980~. Avidin is a protein found in egg white and oviduct
tissue, which binds biotin preventing its absorption (Fraps et
al., 1943~.
Stout et al. (1966) demonstrated that biotin deficiency
resulted from feeding practical mink diets composed of high
levels (40 percent or more of diet dry matter) of offal from
breeder hen turkeys. Presence of raw eggs in the offal was pre-
sumed responsible for the deficiency. The deficiency can be
prevented by feeding the offal at subcausative levels, by heat-
ing it to denature the avidin (91°C t196°F] for 5 minutes)
(Stout and Adair, 1970a), or by supplementing the diet with
synthetic biotin. Conventional mink diets do not appear suffi-
ciently rich in biotin to counteract avidin.
Signs of Deficiency The biotin deficiency that results from
feeding the offal from laying hen turkeys causes gray or
banded underfur in dark mink (see Figure 5) and, in extreme
cases, hair loss. When fed biotin-free purified diets, the defi-
cient animals showed "spectacle eyes," crusty feet, yellow or
bloody exudate, and a dermatitis of the foot pads in addition
to the gray underfur (Travis et al., 1968~.
Biotin deficiency has been experimentally produced in mink
by feeding raw egg white as 30 percent of the dietary protein
(Helgebostad et al., 1959~. Signs noted were pronounced
achromotrichia, reduced fur quality, hair loss, degenerative
changes in the hair follicles, thickened and scaling skin, con-
junctivitis, fatty infiltration of the liver, and ultimately death.
There are wide differences in the effects of feeding similar
levels of chicken and turkey eggs to mink. From results of mink
feeding trials, it appears that turkey eggs contain three to four
times as much avidin as do chicken eggs (Stout and Adair,
1969~. Inclusion of as little as 5 percent of spray-dried chicken
eggs in mink diets unsupplemented with biotin may also cause
fur graying (Wehr et al., 1980) and total reproductive failure
(Aulerich et al., 1981~.
Folic Acid
Based on observations of Schaefer et al. (1946), a level of 0.5
mg per kilogram of dry feed, or 0.135 mg per 100 kcal ME, has
been suggested as an adequate level of intake. Given at this
level, folic acid caused remission of deficiency signs (growth
stunting, diarrhea, and loss of appetite); however, levels
below this were not fed. This level is lower than that found in
typical diets fed to ranch mink.
Niacin
The mink requires niacin in the diet, because it is unable to
convert sufficient tryptophan to meet its niacin requirement.
Mink gained weight when fed a purified diet supplemented
with 0.5 mg of niacin per 100 kcal ME, but lost weight and
died when supplemented with 0.25 mg of niacin per 100 kcal
OCR for page 14
14 Nutrient Requirements of Mink and Foxes
ME (Warner et al., 1968~. It is unlikely that supplementation
of typical mink diets is required, since they have been shown
to contain 50 to 75 mg per kilogram of diet, or approximately
1.25 to 1.87 mg of niacin per 100 kcal ME (Rimeslatten,
1966a; Utne, 1974~. Mink milk is unusually high in niacin.
Joergensen (1960) found 16 mg of niacin in 100 g of mink milk,
which is about 20 times the concentration found in cow's milk
and twice that found in the milk of the sow.
Signs of Deficiency Young mink fed on a niacin-deficient
diet by Warner et al. (1968) displayed rather nonspecific
symptoms, including loss of appetite, loss of weight, weak
voice, general weakness, and a bloody stool. More than 50
percent died within 6 days after being placed on the niacin-
deficient diet.
Pantothenic Acid
Studies by McCarthy et al. (1966) placed the requirement for
pantothenic acid at 0.20 mg per 100 kcal ME.
Signs of Deficiency Early signs of deficiency were loss of ap-
petite and reduced serum cholesterol levels. Blood appeared in
the feces 8 or 9 days prior to death and continued to death.
Clinical findings were diarrhea, weakness, emaciation, and
dehydration.
vitamin B6
Vitamin B6 exists in three interconvertible forms: pyridoxine,
pyridoxal, and pyridoxamine. Of these, pyridoxine is the most
commonly used as a supplement in animal diets. The vitamin
B6 requirement for growth and normal metabolism, using
purified diets, was 1.6 mg per kilogram of feed, or 40 ,~g per
100 kcal ME (Bowman et al., 1968~.
For reproduction, studies by Rimeslatten and Aam (1962)
indicated that the requirements were not met by 3.2 ma, but
that they could be met with 9.5 mg of pyridoxine per kilogram
FIGURE 5 Marginal biotin defi-
ciency in dark mink. Pelts are parted
to show underfur. Left to right: Nor-
mal, gray, and gray-banded underfur.
SOURCE: F. M. Stout, Oregon State
University, Corvallis.
of dry feed (approximately 80 and 237 ,ug per 100 kcal ME).
Joergensen et al. (1975) found increasing blood levels of
vitamin B6 with feed levels up to 14 mg per kilogram of dry
matter, while 30 mg of the vitamin per kilogram gave the
same blood levels as 14 ma. Studies by Akimova, cited in
Feeding Fur Bearing Animals (Perel'dik et al., 1972), in-
dicated that a vitamin B6 deficiency during growth influenced
the breeding results of the following reproduction period.
Signs of Deficiency Signs of deficiency in growing kits ap-
peared after about 2 weeks on a purified vitamin B6-deficient
diet and included reduced feed intake, loss of weight, diar-
rhea, brown exudate around the nose, excessive lacrimation,
swelling and puffiness around the nose and face region,
apathy, muscular incoordination, convulsions, and finally
death unless relieved by supplementation with vitamin B6
(Bowman et al., 1968).
A deficiency of vitamin B6 during the reproductive cycle
reduced the number of females conceiving and lowered the
number of kits per litter (RimeslAtten and Aam, 1962~. Mink
fed desoxypyridoxine, an antagonist of pyridoxine, did not re-
produce due to resorption of the embryos by females. There
was also a degeneration of the testes in males (Helgebostad et
al., 1963~.
Riboflavin
Based on studies using purified diets, Leoschke (1960) deter-
mined riboflavin requirements for growing kits to be about
1.5 mg per kilogram of dry feed, or 40 ,ug per 100 kcal ME.
Short-term trials with fully grown mink Joergensen et al.,
1975) showed unchanged levels in blood, muscles, and organs
with levels of from 4.5 to 26 mg riboflavin per kilogram dry
matter of feed.
Signs of Deficiency Mink fed purified diets unsupplemented
with riboflavin showed loss of appetite, weight loss, and ex
OCR for page 15
Nutrient Requirements of Mink and Foxes 15
treme weakness. Effects of deficiency started after about 2
weeks on the riboflavin-deficient diet (Leoschke, 1960~.
Akimova (1969) stated that poor breeding results were ob-
tained from animals fed diets deficient in riboflavin during
growth, even though adequate amounts were fed thereafter.
T7 ·
Gamin
Young mink fed a purified diet required 1.2 mg of thiamin hy-
drochloride per kilogram of dry feed, or 33 ,ug per 100 kcal ME
(Leoschke and Elvehjem, 1959~. Short-term trials with fully
grown mink Joergensen et al., 1975) showed marked increase
of thiamin levels in muscles and heart when thiamin supple-
ments from 2 to 24 milligrams per kilogram of dry matter
were fed. The urinary excretion increased from 6 to 230 ,ug
thiamin per animal per 24 hours.
If the animals are fed raw fish containing the enzyme thi-
aminase, thiamin is destroyed. Since thiaminase is heat-labile,
the problem can be avoided by cooking the fish at 83°C
(181°F) for at least 5 minutes before adding to the other diet
ingredients (Gnaedinger and Krzeczkowski, 1966~. Another
practical procedure is to include thiaminase-containing fish
only on alternate days and give a thiamin supplement. Table
15 presents a list of fish containing thiaminase. Oregon studies
showed that the diet consumed by the fish has an important
bearing on whether thiaminase will be present (Stout et al.,
1963~. That is, fish listed as thiaminase-free may ingest thiam-
inase-containing fish and consequently create a secondary
thiamin deficiency. In Scandinavia, when thiaminase-con-
taining or ensiled fish are used at a level higher than 10 percent
of the diet (wet basis), the urinary excretion of thiamin is
monitored and not allowed to go below 150 ,ug per animal per
24 hours (G. Joergensen, National Institute of Animal Science,
Hilleroed, Denmark, personal communication, 1978~.
Signs of Deficiency Thiamin deficiency was first observed in
adult mink fed Columbia River smelt (Long and Shaw, 1943~.
The first obvious sign was failure to eat; emaciation and weak-
ness rapidly followed. After 6 or 7 days, affected animals ex-
perienced convulsions, which led to a state of collapse and in-
ability to move. Diarrhea usually accompanied the last stage
of the disease, and the fur on the posterior parts became coated
with thick, black fecal excretions. This final stage lasted only a
few hours, after which death occurred.
Mink kits started on a thiamin-deficient purified diet at 8
weeks of age began to show thiamin deficiency (Chastek pa-
ralysis) in 3 weeks (Leoschke and Elvehjem, 1959b). Signs
were anorexia, loss of weight, lack of muscle coordination, ex-
treme weakness, and, finally, paralysis and death.
Animals displaying anorexia, loss of coordination, and con-
vulsions due to thiamin deficiency may recover following a
single intraperitoneal injection of thiamin hydrochloride solu-
tion. If mink are still eating, supplementing feed with thiamin
will restore the animals to good health.
vitamin Bi2
A level of 30 ,ug per kilogram of dry diet, or 0.8 ,llg per 100 kcal
ME, has been found to meet the requirement for growth
(Leoschke et al., 1953; Leoschke, 1960~. The actual require-
ment may be lower. This requirement is usually met by practi-
cal mink diets containing large quantities of animal protein.
Signs of Deb ency Mink affected by experimental vitamin
BE deficiency show anorexia, loss of weight, and severe fatty
degeneration of the liver (Leoschke et al., 1953~.
Other Nutrient Factors
Although no definitive work has been done on inositol, a level
of 250 mg per kilogram of dry feed was apparently adequate
for mink that were fed purified diets (Leoschke, 1960~. Fin-
nish investigations Uuokslahti et al., 1978) confirmed Russian
recommendations of giving mink a supplementation of 20-40
mg choline per animal per day. In the actual experiment, 40
mg choline chloride could prevent fatty liver and improve the
hepatic function in mink.
MINERALS
General
The relative requirements for mineral elements by mink cover
an exceedingly wide range. For example, satisfactory produc-
tion results (Kangas, 1974) have been obtained from mink ra-
tions containing over 3,000 times as much calcium as copper.
All mineral guidelines are given on a dry matter basis unless
otherwise stated. The composition of mineral sources com-
monly used as feed supplements is shown in Table 14.
Calcium and Phosphorus
For growing mink, calcium-to-phosphorus ratios between
1.0:1.0 and 1.2:1.0 have been recommended (Bassett et al.,
1951~. Under optimal conditions the minimum calcium and
phosphorus requirement may be below 0.3 percent (Bassett et
al., 1951~; however, in practice it appears that growing mink
require 0.4 to 1.0 percent calcium and 0.4 to 0.8 percent phos-
phorus if vitamin D is provided at a concentration of 820
IU/kg dry feed and the calcium-to-phosphorus ratio is be-
tween 0.75:1.0 and 1.7:1.0 (Rimeslatten, 1966b).
Signs of Deficiency When the diet is deficient in calcium or
phosphorus, bone growth is abnormal.
Signs of Excess Within 10 days after they are placed on a ra-
chitogenic diet high in calcium and low in vitamin D and
phosphorus, mink kits experience difficulty in walking (Smith
and Barnes, 1941~. They tend to crawl, and the condition
becomes more severe until they are unable to stand. Enlarge-
ments of the ribs at the costochondral junctions are evident.
The spinal column in the thoracic region becomes concave
(lordosis). The leg bones bend and enlarge at the ends. The ash
contents of the dry fat-free femurs are 22 to 30 percent, com-
pared with 60 to 64 percent for normal animals.
OCR for page 16
16 Nutrient Requirements of Mink and Foxes
Sodium and Chlorine (SaltJ
There are no dam on the minimum requirements of the grow-
ing mink for sodium and chlorine; however, 0.5 percent salt in
the wet feed (Hartsough, 1955) or 1.3 to 1.5 percent salt in the
dry diet (Glem-Hansen, National Institute of Animal Science,
Hilleroed, Denmark, personal communication, 1978) has
been suggested for pregnant and nursing females to prevent
"nursing sickness," a condition that sometimes occurs during
the latter stages of lactation. Sodium and chloride re-
quirements at other times may be lower. Excessive salt intake
is harmful. For example, Perel'dik et al. (1972) suggest that
1.5 percent added salt (dry basis) fed during growth results in
reduced reproduction during the following breeding period;
however, supporting data were not presented. Problems of
salt toxicosis may be aggravated by reduced water intake.
Potassium
In the absence of precise requirements, Wood (1962) has sug-
gested an amount equivalent to approximately 0.3 percent
potassium for breeder and grower diets. Since potassium is
plentiful in most plant materials, it may be expected to be ade-
quately supplied in mink diets containing normal amounts of
cereal (10 to 30 percent).
Magnesium
Considerable diversity of opinion exists concerning recom-
mended minimum required levels of magnesium. Wood
(1962) has suggested an amount equivalent to 440 and 396
mg/kg in breeder and grower rations, respectively, while the
data of Warner et al. (1964) suggest 625 mg/kg to be adequate
for normal growth on a purified diet. Evidence has not been
presented that magnesium deficiency is a serious threat to
ranch mink. The level of 440 mg/kg magnesium is tentatively
recommended for mink diets in the absence of more definitive
data. Some antagonism is recognized among magnesium, cal-
cium, and phosphorus. Thus excesses of calcium or phospho-
rus in the diet may decrease the absorption of magnesium, and
vice versa (Glem-Hansen, National Institute of Animal Sci-
ence, Hilleroed, Denmark, personal communication, 1978~.
Iron
The problems of providing adequate dietary iron to mink have
been dramatized by the occurrence of a specific iron-defi-
ciency syndrome, cotton fur or cotton pelt (Figures 6 and 7~.
The precise amount of iron required by mink is not known,
but if no interfering factors are present, 20-30 ppm iron is con-
sidered adequate (Ahman, 1966, as cited by N. Glem-Hansen,
National Institute of Animal Science, Hilleroed, Denmark,
personal communication, 1978~. Glem-Hansen (National In-
stitute of Animal Science, Hilleroed, Denmark, personal com-
munication, 1978) has suggested 60 ppm, while Wood (1962)
suggested an amount equivalent to 88 and 79 ppm iron for
breeder and grower diets, respectively. Typical Scandinavian
mink diets contain 156-352 ppm iron, well above this level (N.
FIGURE 6 Cotton fur in mink. Pelts are parted to show underfur.
Left: Cotton fur. Right Normal fur. SOURCE: F. M. Stout, Oregon
State University, Corvallis.
Glem-Hansen, National Institute of Animal Science, Hille-
roed, Denmark, personal communication, 1978~. Feeding
high levels of raw marine fish of the cod (Gadidae)
family such as Pacific hake, Atlantic whiting, and coal-
fish may result in severe anemia and cotton fur. Freezing the
raw fish appears to accentuate the problem, while heating it
to 93°C (200 °F) destroys or inactivates the causative factor
(Stout et al., 1960a). Very high levels of trimethylamine oxide
(TMAO) are present in such fish, and this compound is broken
down by an enzyme present in the fish digestive tract to yield
several products, including formaldehyde (FA) (Amano and
Yamada, 1964~. Both TMAO (Ender et al., 1972) and FA
(Costley, 1970; Wehr et al., 1976) have been identified as
causative factors of cotton fur. FA has been shown to interfere
with iron absorption in rats, and feeding FA to mink on a non-
fish diet containing no TMAO has produced severe anemia
and cotton fur. The difficulty can be overcome by supplying
iron parenterally (Stout et al., 1960b); however, feeding of
iron supplements has met with mixed success. Scandinavian
researchers Ender et al. (1972) and Skrede (1974) report ferric
glutamate and ferrous fumarate are satisfactory supplements
for preventing dietary iron deficiency. However, ferric gluta-
mate has been tested with negative results in the United States
(Wehr et al., 1976~. Ferrous fumarate (200 ppm iron added to
the diet) reduced but did not eliminate anemia and cotton fur
caused by feeding FA or 55 percent Pacific hake (Adair et al.,
1974~.
Signs of Deficiency The most easily recognizable sign of iron
deficiency in mink is cotton fur, an almost complete lack of
pigmentation of the underfur. In addition, a microcytic-hypo-
chromic anemia, severe emaciation, growth retardation, and
rough pelage may occur (Stout et al., 1960a) (see Figures 6 and
7~. If anemia is present during critical early phases of fur
OCR for page 17
Nutrients Requirements of Mink and lToxes 17
growth, cotton fur is likely to develop. The earlier and more
severe the anemia, the more pronounced the fur defect.
Zzinc
Wood (1962) has suggested levels equivalent to 66 and 59 ppm
zinc on a dry matter basis for breeder and grower diets, re-
spectively. In practice these levels were met without supple-
mentation in typical Finnish mink diets, which contained 57-94
ppm zinc (Kiiskinen and Makela, 1977~. Since zinc has been
reported to be transported through the skin (Keen and Hurley,
1977), mink maintained in galvanized wire cages might ab-
sorb some zinc from this source. Signs of severe zinc deficiency
have been reported in rats (Hurley and Mutch, 1973), but spe-
cific evidence of zinc deficiency in mink is lacking.
Manganese
The minimum requirement of manganese for normal mink is
not known. Wood (1962) recommends levels corresponding to
44 and 40 ppm for breeder and grower diets, respectively.
These levels were obtained by analysis of adequate diets com-
monly fed to mink on the west coast of the United States and
Canada.
Signs of Deficiency Manganese deficiency has been espe-
cially noted in pastel mink, where it results in symptoms of
"screw necks'' or head tilting. This is a result of a birth defect
in which the otoliths (gravity receptors in the inner ear respon-
sible for maintenance of equilibrium) are reduced in size or
absent. Animals displaying this defect have extreme difficulty
in swimming and, depending upon extent of defect, may be
completely unable to maintain equilibrium and consequently
drown. The syndrome can be prevented by 1,000 ppm man-
ganese supplementation to the mother during embryonic de-
velopment. Additionally it has been suggested that a slight
increase in litter size may accompany such manganese supple-
mentation (Erway and Mitchell, 1973~.
Copper
The recommended level for copper in the mink diet is 4.5-6.0
ppm (Glem-Hansen, National Institute of Animal Science,
Hilleroed, Denmark, personal communication, 1978~. In gen-
eral the copper requirement is adequately met by typical mink
diets containing fish (Kiiskinen and Makela, 1977~.
Iodine
Presence of marine fish in the diet usually implies adequacy of
iodine. Wood (1962) has suggested a level of 0.2 ppm for
breeder and growth diets as adequate iodine levels. Normal
fish-containing mink diets approximate 2.4-6.4 ppm iodine
(Kiiskinen and Makela, 1977~.
Selenium
Data are not available on the minimum requirement for sele-
nium; however, it is assumed that typical mink diets, espe-
cially those containing fish, supply this trace element in suffi-
cient quantities. Kiiskinen and Makela (1977) have reported
several Finnish mink diets to contain 0.05-0.42 ppm selenium
in the dry matter. Stowe and Whitehair (1963) determined
FIGURE 7 Left: Carcass of normal mink. Right Carcass of cotton that 0.1 ppm selenium added as sodium selenite to a tocoph
fur mink. Note the anemic condition of the carcass on the right. erol-deficient basal diet prevented all but minor tocopherol
SOURCE: F. M. Stout, Oregon State University, Corvallis. deficiency lesions in mink (see section on vitamin E).
Representative terms from entire chapter:
body weight
