DOMINION OF CANADA.

THE HONORARY ADVISORY COUNCIL FOR SCIENTIFIC
AND INDUSTRIAL RESEARCH

BULLETIN No. 8

SOME PROBLEMS
OF THE

FOX-RAISING INDUSTRY

BY

ANDREW HUNTER, M.A., B.Sc., M.B., Ch.B., Edin.,

Professor of Biochemistry, University of Toronto

 

Canada

Published by the authority of the Sub-Committee of the Privy Council
for Scientific and Industrial Research

OTTAWA, 1920
SOME PROBLEMS OF THE FOX-RAISING INDUSTRY.

1

INTRODUCTION.

The business of fox-breeding, which in the years before the
Great War was little more than a speculative adventure, is today
a solid commercial enterprise, success in which depends entirely
upon the number and quality of ‘the pelts actually sold. In this
character it has already attained a truly surprising magnitude.
In Prince Edward Island alone there are about 275 fox farms with,
it is conservatively estimated, at least 4,000 pairs of breeding
foxes. During the season 1918-19 there were offered for sale,
at prices ranging mostly’ from $250 to $1,000, approximately
5,000 skins, and the total revenue of the Island from this source
must therefore have been little short of $1,000,000. When it is
considered that this province is not the only. one in which foxes
are raised for their fur (ranches Kave been established also in New
Brunswick, Quebec, Ontario, Manitoba, etc.), and when it is
further realized that the pelts produced are practically all exported;
it becomes evident that the.industry may: justly claim not merely

~a local, but a national importance, which is very far indeed ‘from

being negligible. Needless to say, it has not reached this status
without encountering a variety of difficult problems. It is the
purpose of the following pages to inquire into the nature of these,
and to consider whether it would be profitable, and in.what manner
it might be peer to attempt aa solution. —

I. THE AVERAGE Visits AND THE PossIBILITyY OF .ITs >

, _ IMpRoveMENr. wba

It can hardly ‘be doubted that under existing circumstances
the, returns of the industry are on the average lower than. they
need be. It is, to be sure, impossible to ascertain with exactness
either the total number. of fox pups born in a given year, or the
total number raised to maturity; but the information available
would suggest that the 4,000 pairs of adult foxes in Prince Edward
Island raised successfully last year not much more than 5,000

74506—1 1
pups. This would bean average yield of only 1-25 per pen. Since
the number at a birth is seldom less than 3, and is often from 5 to 7,.
it is obvious that such a figure indicates either a large percentage
of infertile matings, or very considerable losses among the growing
pups. The exact importance of the first factor cannot at present bé
even roughly estimated, but as regards the second it would appear
to be established, upon the independent testimony-of many exper-
ienced breeders, that from 40 to 60 per cent of the foxes actually
born never reach maturity.. The losses thus indicated are largely
avoidable, for there are individual ranches where the yield is very
much higher than the estimated average. In many it is over
2-5, and it appears that it may sometimes even exceed 4. What
can be accomplished by some ranches ought not to be impossible
to any. It would be hard to say what may be the practical limit
of improvement, but if the actual yield be taken as 1-5, and the
generally attainable set no higher than 3, it would seem not
unreasonable to hope that the revenues of the industry might,
by scientific management, at least be doubled.

II. Factors RESPONSIBLE FOR THE Low RATE oF INCREASE.

The factors responsible for the low average rate of increase
are evidently very numerous, and are not always readily deter-
minable; but most of them appear to be classifiable under one or
other of the following heads:

1. Infectious Diseases.
2. Parasites.

3. Food Poisoning.

4. Imperfect Nutrition.

1. INFECTIOUS DISEASES.

Several ranches are known to have been visited by distemper
within the last few years, and it is suspected that others have
suffered without permitting their misfortune to become public.
While the loss thus caused to the industry as a whole represents
probably but a small fraction of the total revenue, a single outbreak
may spell at least‘ temporary disaster for the individual.

It hardly needs to be said that the problem presented by
distemper is mainly one of prevention. From this point of view
the existing practice of many ranches is certainly capable of

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improvement. It ought for instance to be a matter of routine,
that every fox introduced from another locality should undergo
before admission a regular period of quarantine. Not only so,
but the foxes should be more rigidly isolated than at present from
every contact, direct or indirect, with other animals. It is not
definitely known what species are, and what are not, capable of
harboring or transmitting the specific virus of distemper; but
it would obviously be the part of wisdom to exclude every kind
of animal, domesticated or wild, not only from the neighbourhood
of the fox ranch, but also from the society of the keeper.

Should distemper once make its appearance in a ranch the
most strenuous steps must be taken to prevent its spread. The
only hope of doing so, apart from.the use, as yet in its experimental
stage, of protective vaccines, lies in the prompt and complete
isolation of the affected animals, and the thorough disinfection
of their pens. Such a procedure presupposes of course the pos-
session by the infected ranch of a special group of pens, separated
from its regular system, and capable of serving on occasion as a
quarantine station, an isolation hospital, or a special nursery for
backward pups. Every fox-breeder will probably admit the
desirability of such an arrangement; but there are few as yet who
have put it into operation. l

2, INTESTINAL PARASITES.

(4) Rounp Worms.—The majority of the fox pups on Prince
Edward Island would appear to become infected by the round
worm, several varieties of which have been encountered locally,
almost as soon as they are born. How far this almost universal
infection is responsible, under existing conditions, for the high
percentage of loss among the youngest pups, it is not very easy
tosay. It has become part of the regular routine of nearly every
ranch to administer to cach pup, at the end of the 3rd and 4th,
and again at about the eighth week of life, some one or other of
the various vermicidal preparations upon the market. Many
ranchers state that since this practice has been generally adopted
the round worm no longer constitutes a serious problem; others
regard it still as their most formidable enemy. My own impres-
sion is that the latter view is more probably the correct one, and
that many of the pups found dead in their nests, or carried out

74506—2 3
and buried by the mother, would, if the matter -were investigated,
be found to have been killed by round worms. This is one of.
many points which might well be made the,subject. of careful
inquiry.

The pups are generally assumed, probably quite correctly,
to acquire the infection during suckling, the teats of the mother
fox having become contaminated with the eggs of the parasite
through contact with such material as soil, feces, or the bedding of
the nest. It is almost certain that the eggs of the round worm
exist, and survive the winter, in the soil of every ranch where
the parasite has been prevalent; and it is probably of some signifi-
cance that early litters, born while the snow is yet upon the ground,
are, as experienced caretakers maintain, less liable to suffer from
worgns than the later ones. Unfortunately many of the state-
ments made regarding round worms in the domesticated fox have
rested hitherto upon analogy rather than upon actual observation.
It is desirable that they should be tested upon the ground, and that
the precise mode in which the fox becomes infected, together with
the details of the parasite’s life history in this particular host,
should be established once and for all in an authoritative manner.

Another aspect of the subject which deserves investigation
is the possibility of attacking the parasite not after, but before”
it has gained entrance into the new born pup. If it were possible
to destroy in the fall all the worms or eggs infesting the adult
foxes, the dens, and. the soil of the ranch, there could be no infection
of pups in the following spring. This would be a more logical
method of procedure than the one now prevailing; whether it is a
practicable one can be determined only by experiment.

The worms and their eggs, expelled as a result of treatment,
are frequently allowed to lie unmolested in the pens wherever
they happen to fall. In view of the highly resistant properties
of the eggs this would appear to be a very careless procedure. It
should be possible to devise some way by which they could be
collected in one spot, and immediately destroyed. The observance
of such an elementary precaution would probably do something
to diminish the probability of reinfection.

Widely as the round worm is now distributed among the
Island ranches, it would probably be an error to regard it as a
necessary evil. Ranches exist in which it is alleged that worms

4
have never been seen, and in which accordingly treatment has
never been practised; in others the infection is limited apparently’
to two or three adjacent pens. It is possible that a rancher
starting afresh could by taking proper. precautions, the nature of
which will readily suggest themselves, stock his pens in such a
manner as to harbor not a single worm, and could maintain them
indefinitely in that condition. With this problem, as with that

‘of distemper, preventive measures should in the future assume a

~

predominant role. It should, for instance, become a matter of
routine to examine for eggs the feces of any new fox, which it is
proposed to introduce into a ranch; and in case these are found, to
subject the animal before admission to the most efficacious course
of treatment that can be devised. Laboratory control of some sort
would of course be necessary to the complete success of such a plan.

(8) Hookworms.—The Health of Animals Branch of the
Dominion Department of Agriculture has recently found that
many domesticated foxes are infected by the hookworm.
The presence of this parasite cannot fail to have deleterious effects
upon the health and vitality of the animal harboring it. Just
how extensive and how serious these effects may be remains to
be determined. In any case it will be necessary in the future
for the fox breeder to pay attention to this hitherto unsuspected
enemy, and to initiate measures for effectively controlling its
spread. He can hardly do so without the advice of an expert,
and the assistance afforded by a readily accessible laboratory.

3. FOOD POISONING.

Acute food poisoning has on several occasions been responsible
for serious losses among both young and adult foxes. This could
occur only when the rancher had not taken sufficient care to
ascertain the fitness for consumption of the meat he was feeding.
It would obviously be to the benefit of the industry as a whole
if it adopted some general co-operative system, whereby all meat
intended for foxes should be first inspected, and then properly
stored in cold storage plants at a sufficient number of readily
available centres.

4. IMPERFECT NUTRITION.

However important the factors of loss hitherto discussed,
their elimination would leave the average yield of the ranches still

5
lar below its ‘possible maximum. The fundamental problem of
the fox farmer, as of every breeder of animals, is one of nutrition;
and it is the failure fully to solve this problem that occasions at
present the most serious losses to the industry.

If a fox, or any other animal, is to be maintained through
life in perfect nutritive condition, its diet must conform to each
and all of the following requirements. (1) It must furnish protein
(flesh-building food) in such quantity and also of such quality as
will make good the wear and-tear of the body tissues, and provide,
in young antmals, material for growth. (2) It must have an
adequate fuel value or energy content (commonly measured in
heat units or calories), a requirement best met by supplementing
the necessary protein with carbohydrates (starchy foods) and fats.
(3) It must contain proper amounts of certain indispensable
mineral clements, such as phosphorus, calcium (lime), iron, and
the like. (4) It must include a sufficient supply of the so-called
vitamines, essential accessories of unknown nature, the absence
of which leads to various types of disordered nutrition, and of
which there are believed to exist at least three, (the ‘‘fat-soluble
the ‘‘water-soluble’”’, and the ‘‘antiscorbutic’’).

To what degree these requirements are met, or fallen short of,
in one fox ranch or another, it is not at present possible to decide.
It is of course easy enough to obtain a list of the articles that make
up the foxes’ menu; but to ascertain, item by item,, the actual
food consuniption of the individual animal, (which is what really
counts), is quite another matter. Such information, as it has
hitherto been possible to collect, touches merely the qualitative
aspect of the problem. Any attempt, therefore, here: made to
correlate the nutritional disorders reported with specific defects
of diet is to be regarded as purely preliminary in character.

The most striking feature of feeding practice, as it has come
under my observation, is its lack of uniformity. Each ranch
scems to have worked out more or less independently an individual
plan, and, so long as this operates with even moderate success,
it féars to risk a change. Failure and success alike have been

,

largely the result of chance. The diets in use have in short been _

developed largely at haphazard, and, generally speaking, with

few guiding principles other than the supposed habits of the wild

fox. It is assumed, rightly or wrongly, that the latter lives almost
6
exclusively upon flesh, and accordingly meat in one form or another
forms the principal ingredient of nearly every dietary. The
chief variety employed is horse-flesh, most of which is imported
from Montreal or Toronto; coming, as it does, from old and
exhausted animals, it is conspicuously devoid of fat. Other food
materials, entefing into the dietary of one ranch or another, are
listed below;

Meat: (besides horse-flesh), beef, mutton, veal, pork, rabbit
and chicken. Fish: smelts, salted fish (with the salt removed by
washing in water). Offal: liver, tripe, the entire viscera of small
animals. Cracklings. Eggs. Milk: whole or separated, raw or
pasteurized, condensed or evaporated. Home-baked bread or
biscuit. Flour: graham flour, whole wheat, cornmeal. Porridge:
oatmeal, barley, rye, wheat, bran. Shredded wheat. Rice.
Fox biscuits of various makes, especially ‘‘cod-liver-oil” biscuits.
. Apples.

It is difficult from a mere list of the sort given to form any
judgment of the general adequacy of the diets consumed. Probably
they satisfy in general the first two requirements that have been
laid: down; there is considerable reason to doubt whether they
fully meet the third and the fourth. It is to be remarked that the
majority of the articles named are drawn from two sources, namely
meat and the cereal grains. A diet absolutely restricted to these
would be decidedly deficient in certain mineral ingredients, for
instance calcium (lime), and would moreover fail to provide a
proper supply of the indispensable ‘‘vitamines’’. The deficiencies
would be all the greater if the meat, like that chiefly fed to foxes,
were practically free from fat. They might be corrected in part
or in whole by the addition of fats, offal, green vegetables, eggs,
or milk. Fats and.fatty portions of meat ought to appear in
the diet of foxes much more liberally than they do, not so much
as vehicles for. the fat soluble vitamine, in which the body fat of
animals is not particularly rich, but in the general interest of a
well balanced ration. Offal, such as liver and tripe, is a good
source of the fat-soluble vitamine, and might with advantage be
much more generally utilized than it is. Greens would supply
not only vitamines but also calcium, though it is doubtful whether
they could be fed to foxes in sufficient quantity to afford any
important supply of the latter. In existing practice they are not

7
fed at all. Nevertheless the fox exhibits an appetite for a certain
amount of vegetable material, and is often observed to nibble
grass or the leaves of trees. This indicates in all probability a
real physiological need, and the deliberate provision of some leafy
materials from time to time might therefore be beneficial. Possibly
some kinds of desiccated vegetable could be successfully utilized.
Eggs are capable of supplying every requirement of a growing
animal, except possibly calcium, and will of course supply this
also if the shell is eaten.. Milk, in sufficient quantity, will make
good any dietary deficiency whatsoever, and the more extensive
use of milk, when necessary suitably modified, would perhaps
solve not a few of the nutritional problems at present confronting
the fox raiser. It is true that milk already occupies a place in the
diet list of practically every ranch I have visited. But it may be
questioned whether the amount fed is universally sufficient to
make good the defects of the meat and cereals which supply the
bulk of the nutriment. There exists among breeders some differ-
ence.of opinion as to the best form in which to administer milk to
foxes. The proper practice would probably be to use only raw
whole milk. To remove the fat is to remove an important nutrient,
in which the diet as a whole is already deficient, and with it the
associated fat-soluble accessory; while to heat the milk is to
destroy or diminish its vitamine content in general, and therefore
seriously to affect its growth-promoting and protective properties.

When cow's milk is used for the feeding of very young foxes,
it ought, we may assume, to be so modified as to approximate in
composition the milk supplied by the vixen. Unfortunately the
exact composition of the vixen’s milk is not known. There is on
record but one analysis, and that a very imperfect one, of a sample
which may or may not have represented a fair average. So far
as it goes it indicates a much higher fat and a much lower sugar
content than cow’s milk. This is quite in accord with what is
known of the milk of small animals in general. It would therefore
seem reasonable to use for the growing pup cow’s milk of the
highest obtainable fat content, and even to enrich this. by the
addition of a suitable amount of cream. But before the fox
breeder can be furnished with authoritative guidance in the adap-
tation of cow’s milk to the successive stages of the young animal’s
growth, it will be necessary to secure more comprehensive and

8
accurate data upon the composition of vixen’s milk, not only in
regard to organic but also inorganic constituents. The immediate
need of such data should not be forgotten in any experimental
work which may be planned in the future.

The dietary imperfections, to the probable existence of which
attention has been drawn, are likely to be most conspicuous during
the winter season. The reason for thinking so is thatmilk4is never
included in the diet until after the pups are born in the early
spring. This situation is the more unfortunate since a diet of
meat and cereals alone furnishes a particularly poor provision for
the requirements of pregnancy and lactation. If the practical
difficulties that have hitherto excluded milk from the diet of the
pregnant female cannot be overcome, other sources of calcium
and of the fat-soluble accessory become an absolute necessity.
Eggs (with the shell) would provide both, bone-meal might be
useful in supplying the former, and the latter could be derived
from the liberal use of liver, tripe and other glandular materials.
Many of the most successful ranchers have been led by experience
to include one or more of these articles of diet in their winter
regime. In others the situation is perhaps saved to some extent
by the use of cod-liver oil biscuits.

Reference has been made to the possibility of a deficiency of
calcium in the diet of the foxes. The other inorganic constituents
of the food also demand attention. Many caretakers appear to
be very much afraid of giving their foxes too much common salt,
and it would not be surprising if this fear led occasionally to a
-deficiency of sodium. It might be a good plan to leave the solution
af this question to the fox itself, by placing in each pen a limp of
rock salt.

A human subject restricted to the articles which have been
actually used in feeding foxes would stand a considerable chance
of being attacked by scurvy. The only foodstuffs-in the list
already given, which contain the ‘‘anti-scorbutic’’ vitamine, are
milk, which is not particularly rich in it, and probably apples.
Scurvy is a disease from which flesh-eating animals are not positively
known to suffer; it is none the less possible and indeed likely that
they require for the maintenance of perfect nutrition a supply
of the antiscorbutic element present in green vegetables, fruits,
and many tubers. If such a requirement does actually exist, it is

9
‘in most ranches rather imperfectly met. Although apples are fed
liberally in certain of the more successful ones, in the majority
they are used very sparingly if at all. There is much to be said
for their regular inclusion in the diet.

After this general discussion of feeding practice in the fox
industry it remains to consider which, if any, among the actually
prevalent sources of damage or loss may be in whole or in part
the consequence of imperfect nutrition. The list of reported
complaints in which a nutritive defect of some sort may with reason
be suspected to be a factor is, as a matter of fact, quite large. It
would include, e.g., rickets, convulsions, sore eyes, still births, the
abandoning or even the killing and eating by the mother of her
young, premature cessation of milk supply, early death of the young,
failure to grow, failure to reproduce, and imperfect development
of fur. ,

During recent years: there have been conducted in different
laboratories a great variety of experiments in which rats, guinea
pigs, swine, or other animals have been subjected for longer or,
shorter periods to the influence of variously restricted diets.
Among the results of these experiments one may find, singly or
in various combinations, every one of the abnormal conditions
just mentioned. This does not necessarily mean that these are
always to be attributed to a dietary factor. The habit of killing
and eating the young, for example, may be merely a vice, inherited
or acquired, in which case there is nothing to be done but to destroy
the animal. What the experiments referred to demonstrate is
that this, and the other conditions named, may be, and doubtless
often are, the consequence of improper feeding. It is probable
that most of them would become much less common if the foxes
could be assured a diet which supplied continuously each and all
of the factors essential to perfect nutrition.

Incidentally it may be pointed out that we do not know
definitely the normal duration of lactation in the fox, nor its
normal growth curve. These furnish problems that should not be
forgotten in any experimental study of the growing fox’s nutrition.

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III. FURTHER CONSIDERATIONS AFFECTING THE RETURNS OF
THE INDUSTRY.

The problem of reaching and maintaining a maximum return
involves more than the successful rearing to maturity of every
fox that may happen to be born. It is of equal importance that
the number born should be as great as the nature of the case
makes possible. This implies that in any complete study of the
problems of fox-raising questions of fertility and fecundity must
be taken into account. These are undoubtedly in part questions
of nutrition, but other factors—hereditary, psychical, climato-
logical, etc.,—are also in varying degrees involved, and it would
be desirable to have their relative importance more exactly eluci-
dated. ‘

A not irrelevant question is that of the proper age for the first
reproductive effort of the adolescent animal. It has become the
‘practice to mate the foxes selected for breeding purposes at the
earliest possible moment, that is, in the winter following their
birth, while they are yet less than.a year old. It is very doubtful
whether this is a practice to be recommended, and it should be
considered whether it would not in the long run be more economical
to postpone mating till the animals reach their second winter. A
series of comparative tests might be planned to throw light upon
this problem.

Again, mere numbers is not enough. The final aim of.the
fox-industry is the production, not so much of perfectly nourished
and healthy animals, as of valuable pelts. These are by no means
necessarily the same thing. A red fox may be physiologically as
perfect an animal as it is possible to conceive; in the market value
of its fur it may be far surpassed by a pure-bred silver fox exhib-
iting the worst deformities of rickets. The fox in captivity is
bred in short for certain special characters, and a failure to present
these in perfection is as definitely.a source of loss to the owner,
as early death. from malnutrition. Beside the fundamental
problem of nutrition we must place therefore the fundamental
‘problem of breeding and inheritance. The more important
aspects of this problem, as related to the fox industry, will be
discussed in another publication of the Research Council.

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IV. RECOMMENDATIONS.

The preceding paragraphs have indicated the existence, in
connection with the fox-breeding industry, of a large variety of
unsolved problems. Their final solution must await the outcome
of appropriately planned experiments. The information collected
is however already sufficient té suggest certain improvements in
existing practice. These may for convenience be thrown together,
here in the form of recommendations addressed to the fox-breeder.

1. An endeavour should be made to supply in the diet more
fat, a certain amount of green vegetables, and. especially more
milk, the fat of which ought not to be removed. A special
endeavour should be made to feed milk during the winter, in which
atteinpt the possible usefulness of whole milk powder should be
remembered. The winter diet should also contain liberal amounts of
tripe, liver, and eggs. Raw apples should be fed whenever it is
possible to obtain them, as well as, if they Prove acceptable to the
foxes, raw potatoes or turriips.

2. A lump of rock salt should be placed in each pen.

3. The adult foxes should be treated for worms in the*fall,
and an endeavour should be made to exterminate all eggs in the
pens before mating takes place.

4. All wild or domestic animals should be rigidly excluded
from the neighbourhood of the pens.

5. Each ranch should maintain a small quarantine station
and isolation hospital.

6. Cold storage plants should be provided for the different
sections of the island; and provision should: be made for the
careful inspection of. all meat fed to foxes.

7.. It would probably be wise to abandon the practice of mating
young foxes in their first year’ of life. :

8. The fox-breeders should. form an | association jae fie: regis,
tration of their valuable animals, and each should - maintain. a
continuous record of the actual performance of its stock,..

12