推 hansel1007:好文～有養寶貝貂的真該好好看看，別只是趕流行 09/09 15:04
推 priorart:謝了 轉寄給我有養貂的朋友 09/09 15:07
推 qzpm:特別註明一點:現已少用Mitotane (Lysodren)，多採用Melatonin 09/10 01:54
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推 littlecooky:推~好專業 09/10 02:10
國內養貂人口持續的上升，但是許多養貂飼主或許會發現，許多貂在四歲後容易發生
Adrenal Gland Cancer而最後致死，有些飼主流傳因為太早結紮，導致內分泌失調。
但事實上，主要的原因是源自於貂所暴露的光照時間，而影響生理週期。這裡指的光
包含各式各樣，月光，太陽光，人工光照。都會影響貂的內分泌，實驗結果，限制光
光照，可以大大降低Adrenal Gland Cancer發生的機率。在秋冬，一天最好限制在八
小時的光照，而在春夏一天最好限制在12小時的光照。因為台灣的氣候，和飼養環境
，往往白天光照時間長達12小時，夜晚又受到人工光照射6小時。對於貂來說，實在
過長。因此你可以用黑布或是其他能阻止"任何"光照的來源的方法來解決。因此建議
白天時，不要讓它照到日光，晚上再放出來。如果當你發現，你的貂越來越胖，又沒
有其他因素影響的前題下，就代表您的貂，原本暴露於光照的時間過長。
如果您對於這件事情很感到興趣，請您仔細閱讀下篇文章。保護您的貂。
Adrenal Gland Cancer
Judith A. Bell, DVM, PhD
Veterinarian, Author, Internationally recognized expert on ferrets
This article was adapted from the "The Pet Ferret Owner's Manual" for
PetEducation.com and is used with permission from Judith Bell, DVM, PhD.
Adrenal gland tumors are common in ferrets over 4 years old. The normal
adrenal gland contains several types of cells that produce different hormones,
such as cortisone and some male and female hormones. Excessive amounts of
female hormones are often produced by adrenal gland tumors. There are no blood
tests that absolutely prove that a ferret has an adrenal gland tumor, because
the hormones and their effects are so variable. Palpation, radiography, and
ultrasonography are used to identify an enlarged adrenal gland. The enlargement
may be caused by hyperplasia (normal cells proliferating at an unusual rate),
or by a benign or malignant tumor.
Possible cause of adrenal gland tumors
Early spaying or neutering. It has been suggested that spaying and neutering 6-
to 7-week-old ferrets induces adrenal gland tumors. The theory is that the
adrenal glands of animals spayed or neutered very young might try to compensate
for the lack of normal sex hormones by proliferation of cells that produce sex
hormones. However, many ferrets spayed or neutered when much older have
developed adrenal gland tumors, and occasionally animals that have not been
spayed or neutered also have adrenal gland tumors.
Individual people and animals are more susceptible to some types of cancer than
others. Some ferret families may be especially susceptible to adrenal gland
cancer. It is likely that more than one factor determines any ferret's
susceptibility to adrenal gland abnormalities. Early spaying or neutering is
certainly not the whole answer, and may not even be part of the answer. The
disease was uncommon in the hunting ferrets that were their ancestors, and is
still rare in animals that live outside, as they tend to do in the UK and in
Australia. The incidence of adrenal gland problems is increasing in the UK as
pet ferrets begin to share their owners' homes instead of living in the back
garden.
Extended photoperiod. It is possible that the incidence of adrenal gland cancer
has increased because we have forced our ferrets to adapt to our life style.
Ferrets are strongly affected by photoperiod. Under natural conditions, there
are only about 8 hours of strong light a day in the winter months, and the
proportions of light and dark gradually change during the spring and fall. We
have removed all these stimuli when we keep the ferret in a house where
electric lights extend day length to at least 12 hours, all year round.
Changing photoperiod causes the ferret to lose weight and hair in the spring,
and come into breeding condition. In the fall, as the hours of light decrease,
ferrets stop breeding, grow a heavy winter coat, and put on extra fat to
prepare for the cold weather. A primitive part of the brain called the pineal
gland mediates the ferret's response to light. The pineal gland produces a
hormone called melatonin only during hours of darkness. Melatonin reduces the
output of gonadotrophins from the pituitary gland. Gonadotrophins bind to cells
in the ovary or testicle, inducing production of sex hormones. The same
gonadotrophins also bind to cells in the adrenal gland. When ovaries and
testicles are removed, these gonadotrophins can bind only to adrenal cortical
cells.
It is possible that constant stimulation of the adrenal glands because of the
long hours of light eventually causes first benign hyperplasia (enlargement),
and then benign tumors to develop in the adrenal cortex. In some animals, the
tumors become malignant or are malignant from the outset. Whether the condition
is hypertrophy, a benign tumor, or cancer, excessive levels of adrenal cortical
hormones are produced.
Hyperplasia may be corrected if the ferret is put in a place where the light
can be limited to 8 hours a day, and the ferret's hair starts to regrow 3 to 6
weeks after the change. By definition, tumor cells are out of control, and
modifying photoperiod cannot reverse hair loss when any type of tumor is
producing sex hormones.
home from work, so the ferret is exposed to natural light all day, and
artificial light in the evening. The obvious way to limit the ferret's exposure
to 8 hours of light a day, without preventing him from interacting with his
family, is to give him a dark place to sleep during the day. It has to be
really dark, excluding all light, like a moonless night.
This might be arranged by putting the ferret's cage inside a well-ventilated
closet, or using light-excluding drapes on the windows in the ferret's room.
Reducing the ferret's exposure to light usually results in an improvement in
coat condition and an increase in body weight a few weeks after the new
arrangement - these responses show that the original photoperiod was too long.
Providing short days only during the winter months is sufficient, as this
mimics the natural seasonal variation in day length.
In a survey of about 300 ferrets performed in the Chicago area in the early
'90's, the lowest incidence of adrenal gland tumors was found in ferrets used
for breeding, and these animals must have been housed under short photoperiod
at least part of the year or they would not have been productive. The
association between adrenal gland tumors and artificial light conditions cannot
be ignored.
Even if there is also some association with removal of gonads, the risk of not
spaying is far greater than the chance that a spayed jill will develop adrenal
tumors at a young age. About 50% of unspayed jills left in heat too long will
develop bone marrow hypoplasia and die, but under natural light conditions, a
very small percentage of ferrets spayed at any age develop adrenal tumors.
Modifying your home to provide a more natural photoperiod in the winter is a
simple thing compared to any of the alternatives once a ferret is diagnosed
with an adrenal gland tumor.
Signs that a ferret has an adrenal tumor
Sometimes weight loss, hair loss, and itching for no apparent reason, are the
only early signs of adrenal cancer in either a male or female ferret. Intact
hobs with adrenal tumors might have permanently enlarged testicles but will be
sterile. The first sign noticed by the owner of a spayed female with an adrenal
gland tumor is often the sudden appearance of a swollen vulva, as if she were
in heat.
Causes of hyperestrogenism in jills
There are two common reasons for jills coming in heat long after they have been
spayed. A mistake made during the spay surgery is not one of them. A jill
spayed incompletely as a kit comes in heat at 4 to 6 months old, depending on
the hours of light each day, the same as if she were not spayed at all.
1. Ectopic ovarian tissue. Occasionally ovarian tissue grows at the site of the
spay surgery, or elsewhere in the abdomen. It is not regrowth of an ovary, it
is new tissue that functions like an ovarian follicle, producing estrogen. This
may happen years after the spay, for unknown reasons. If the jill is left in
heat a long time, she can suffer the same side effects as with a normal estrus,
including loss of hair and suppression of bone marrow. Surgical removal of the
abnormal tissue immediately ends the estrus and its side effects. Injectable
hormones, that work well on normal jills in heat, do not always work on jills
with ectopic ovarian tissue.
2. Adrenal gland tumors. Exploratory surgery may be necessary to distinguish
jills with adrenal gland tumors from those with ectopic ovarian tissue. It is
possible for a jill to have both problems at once.
Prognosis for ferrets with adrenal gland tumors
If left untreated, ferrets with adrenal gland tumors usually lose all but the
hair on their heads and a tuft on the tail tip. Their skin gets very thin, they
have a pot-bellied appearance, and they sleep most of the time. Fortunately,
although they have an odd appearance with almost no fur on their bodies,
ferrets with benign adrenal gland tumors can live a reasonably normal life, if
they do not become anemic due to high levels of estrogen. Jills often appear to
be in heat, and because this is associated with a swollen and open vulva, they
are susceptible to urinary tract infections. Neutered or intact male ferrets
may develop life-threatening urinary obstruction because high hormone levels
cause the prostate gland to hypertrophy (enlarge) and constrict the neck of the
bladder.
The most effective treatment is to surgically remove the abnormal adrenal
gland. This is the only choice to relieve prostate hypertrophy, which it does
within 48 hours. The adrenal glands produce many important substances required
for life. If there are tumors on both glands, one can be removed, but part of
the second one must remain, even if it means leaving part of the tumor there,
too. New techniques using cryosurgery have made removal of an adrenal gland a
safer procedure, and most ferrets recover uneventfully.
Mitotane (Lysodren) is a drug that reduces the amount of hormone being produced
by a benign inoperable tumor, extending the quality life time of the ferret.
Other drugs used in humans are being tried in ferrets.
Some tumors are malignant and do not respond to Lysodren or other treatments.
They metastasize to other organs or recur after removal. Ferrets with malignant
tumors have a short life expectancy after diagnosis.
Reference:
http://www.peteducation.com/article.cfm?cls=11&cat=1292&articleid=522
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※ 編輯: qzpm 來自: 219.80.140.187 (09/09 14:39)