European mink captive breeding
E - European
Mink Captive Breeding Protocol
1. Female European Mink - Detection
of Oestrus
The walls of vagina are lined with epithelial
cells and at the onset of oestrus will cause these cells to become
cornified. Non-cornified cells, which are quite small, round and
with a distinct nucleus, are found when anoestrous vaginal flushes
are taken and examined. A few cornified cells are found in pro-oestrus
flushes. The onset of oestrus is characterised by a 90% vaginal
cornification. Cornified cells are large, flaky cells without
nucleus.
From March 1st, females will be subjected to weekly flushes during
anoestrus and early pro-oestrus periods. When the quantity of
cornified cells are greater than 50%, then vaginal flushes must
be conducted on every third day. When 90% cornifications is achieved
the female must then be placed with an appropriate male for breeding.
Measurements of vulva swelling and evaluation of vulva appearance
will be conducted concurrently with vaginal flushes. It helps
to predict a proper time for pairing, especially while having
only a few breeding pairs of mink, or when the use of vaginal
smears may seem to be too complicated a method to use.
Detection of heat can be indicated by the size of the vulva, when
in full heat the vulva is swollen. In comparison, the size of
the anoestrus vulva is minute, measuring a maximum 2 mm to 4 mm,
but usually much smaller. When the female begins to come into
heat, the vulva enlarges over a period of three to four weeks.
Its maximum size may reach 10mmx10mm or more. The colour of the
vulva also changes during heat from pale white during the anoestrus
to pro-oestrus period and to a pink-reddish coloration during
oestrus. The size and coloration of vulva can be easily examined
and measured through the handling cage.
The vulva measurements should be at least 10mm x 10 mm and pinkish
in colour before the introduction of the female to the male for
breeding.
Behavioural changes exhibited by the female may also provide a
good indicator of heat, where the oestrous female becomes more
active and less timid.
2. Male European Mink - Detection of Fertility
Starting from February 1st, the testes should be measured on a weekly
basis. The testes may grow up to 18mm x 16mm. If the size of the
testes remain relatively small by the beginning of April, it usually
indicates a male of poor breeding quality.
Nevertheless, large testes are not always indicative of a good breeding
male, as very often males with relatively normal size testes are
of equal breeding potential.
3. Breeding Protocol
ANIMAL WEIGHTS
The weights of adult animals are variable within
the sexes and change throughout the annual cycle. Males are considerably
heavier than females, with males also exhibiting a greater seasonal
weight change. The following recommendations are based on the
black-footed ferret breeding protocol and therefore should be
taken as general guide and its application may also be dependent
on individual variation.
Adult females older than one year of age, should lose 15%
of their January weight prior to breeding. Their weight should
then be maintained or slightly increased (2-3%) during gestation.
Weights should be taken at a minimum of twice weekly to monitor
weight loss during February and March.
Adult males, older than one year of age, should lose 10%
of their January weight prior to breeding. Their weights should
then be maintained during the breeding season by increasing the
weight/volume of food ration provided.
Juvenile males and females should lose about 10% of their
February 15th weights prior to March 15th.
PAIRING OF ANIMALS
Pairing will begin once females are determined to be in oestrus(based
on the vaginal smear samples or on vulva appearance).
Whenever possible, pairings will be based primarily upon genetic
considerations determined through the recommendations provided
by the species co-ordinator of the breeding programme. If genetically
preferred pairs are incompatible or non-productive, emphasis will
still remain on gaining reproductive success using other pairings
that result in successful mating with the lowest possible inbreeding
coefficient of potential offspring.
Handling and moving the animals should be carried out by the mink
keeper or with other staff with whom the mink are familiar with.
Oestrous females will be paired with successive males until successful
copulation is achieved. If the male is aggressive or the female
is not receptive to the male, the animals should be separated.
However, if the temperament and behaviour of the pair(s) is extremely
conducive then receptive animals can be left overnight and separated
during daylight hours. If copulation occurs it is desirable to
take a vaginal smear to check for the presence of sperm. Each
receptive female should be placed with the same male on three
successful nights. Thereafter no further introductions to the
male will be necessary or should be attempted.
Experience at Tallinn Zoo, but also at other breeding facilities
in Russia (for example, at Novosibirsk) show that usually males
are the main reason of unsuccessful breeding. They either do not
show any interest or exhibit such overt aggression that they have
to be separated before inflicting serious injury to the female.
A single male will be allowed to inseminate no more than one female
per night. The males should be rested one or two nights between
introductions to different females.
If the pair is found to be incompatible they will be separated
and the female returned to her cage. A second introduction can
be tried the following night and if this fails no further introductions
to this male should be attempted.
4. Whelping Management
The breeding enclosure must be isolated from visitors during the
breeding period. Having only the keeper(s) with which the mink
are familiar, to be allowed to care for pregnant or whelping females.
Exchange of keeper(s) during pregnancy or whelping is highly inadvisable,
as it may result in the failure of successful breeding.
Pregnant females should have the choice of at least two nest boxes.
Food must be provided without restrictions to the female with
kits.
The European mink is a mono-oestrus species that typically have
only a single litter each year. If the female resorbs her embryos
or looses her first litter within a few days of birth, a second
oestrus may occur and then a second breeding attempt may be made.
This pattern of reproduction may prove advantageous, at some stage,
as a management tool to increase population size, where a second
litter may be produced by removing live young shortly after birth
and placing them with foster mothers. Such a propagation technique
however must first have the approval of the species co-ordinator.
5. Cross Fostering of Kits
In the case of very large litters(5-6 young) or very small litters(1
young)then cross-fostering may be necessary. Weak or stunted kits
should be selected for cross-fostering.
Cross-fostering can be attempted when the kit(s) are one month
of age, prior to opening of the eyes and onset of hearing. The
foster female to whom the kits are to be introduced should be
locked out of the nest box and the foster kit(s) should then be
placed into the nest with other kits. It helps to scent the newcomers
by rubbing the introduced kit(s) with the existing bedding material
removed from the nest. The operation should be done quickly to
reduce the stress of the female being kept apart from her young.
The introduced youngster(s) can be temporarily marked for identification
by dyeing or cutting away some of the fur.
6. Hand Rearing of Kits
Hand-rearing of kits is not desirable or encouraged. Whenever
possible, cross-fostering is the preferred choice. Abandoned or
orphaned kits reared by foster mothers are exposed to social interactions
that are often absent or impossible to reproduce in animals reared
in isolation.
7. Kit Care
NEW KITS
Newly-born kits should not be disturbed for 7-14 days after birth.
Any form of disturbance may result in the loss of young, especially
by inexperienced primiparous females.
NESTBOX CLEANING
The female should be locked outside of the nestbox before cleaning
commences. Everything must be cleaned as quickly and quietly as
possible. If separation of the female causes aggression or trauma
to the kits, then cleaning should be minimal or stopped.
The box should be cleaned once a day in the morning, but when
the kits start to move around and eat solids, cleaning may also
take place twice a day.
SEPARATION OF YOUNG
The young should be kept with the mother as long as possible.
Normally litter-mates start to act aggressively towards each other
by late-summer and this is the best time for separation. This
can be done gradually starting with the most dominant and aggressive
kits.
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