Anestrus occur in different animals. Anestrus may be due to physiological or pathological factors. Veterinary drugs are now available to treat or reverse anestrus in animals.

1. shareefngunguni@gmail.com
Class work, Unpublished.
LITERATURE REVIEW ON ANESTRUS IN
BITCHES AND OTHER DOMESTIC ANIMALS.
Authored By:
LUANAR,2018
Shareef Ngunguni, BVM

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LITERATURE REVIEW ON ANESTRUS IN BITCHES AND OTHER DOMESTIC ANIMALS.
INTRODUCTION
The reproductive cycles relates to various
phenomena: puberty and sexual maturation,
the breeding season, estrus cycle, post-
partum activity and aging. These
phenomena’s are regulated by various
activities such as genetic, environmental,
physiological and hormonal factors
(Hafez,1993).The basic pattern of the
estrous cycle is the same in all domestic
animals, but some species differences are
found in specific parts of the cycle. The
estrous cycle may be divided into several
phases based on behavioral changes or
structural changes in internal and external
genitalia. These phases are called proestrus,
estrus, metestrus, and diestrus / anestrus in
other animals (Frandson et al, 2009).
Anestrus is a time of complete reproductive
incompetence, marked by reduction in
hypothalamic GnRH content and secretion
with a consequent sharp reduction in LH and
FSH secretion from the pituitary (Youngquist
& Threlfall, 2007).
LITERATURE REVIEW
a) Bitches
Dogs are monoestrus, usually non seasonal,
and spontaneous ovulators (Youngquist &
Threlfall, 2007). Anestrus is the period of
uterine involution /apparent ovarian
quiescence between metestrus and the
subsequent proestrus (Cupps, 1991).During
anestrus there is marked reduction of
hypothalamic GnRH content and secretion
along with sharp reduction of Luteinizing
Hormone and Follicle Stimulating Hormone
secretion from pituitary gland. As a result of
this hypothalamic-pituitary slowdown,
ovaries undergo functional, in active and
atrophy with only a few follicles over 5 to
10mm observed (Youngquist & Threlfall,
2007). Lack of follicular development
causes loss of ovarian steroids in peripheral
circulation, decrease in progesterone and
estradiol. Progesterone concentrations
decrease just before parturition or gradually
after corpus luteum regression in the
nonpregnant bitch (Kustritz, 2003.With
modern veterinary pharmacology
improvement, drugs to shorten anestrus in
dogs have been established. According to
(Kustritz, 2003) Anestrus may be shortened
with the use of dopamine agonists, such as
bromocriptine or cabergoline. Therapy for
shortening of anestrus should not be
instituted before day 90 of anestrus to allow
normal uterine involution to occur.
Bromocriptine is given until proestrus
begins. Emesis may occur as a side effect.
Cabergoline(5 g/kg administered orally once

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LITERATURE REVIEW OF ANESTRUS IN BITCHES AND OTHER DOMESTIC ANIMALS.
daily) also is given until proestrus begins and
reportedly causes fewer side effects than
does bromocriptine. Proestrus generally
occurs after 17-50 days of treatment with
either drug.
b) Other Domestic Animals
Endocrinology of anestrus is the same in all
animals as explained in bitches. Differences
may be in terms of duration of anestrus and
sexual behaviors showing in domestic
animals.
Mares and sheep exhibit seasonal anestrus.
Mares are long day breeders and undergo
winter anestrus. During anestrus there is
concurrent decrease in ovarian activity and
size as explained in bitches accompanied by
passive sexual behavior. Mares’ sexual
behavior toward stallions becomes more
passive and their cervical folds are non-
edematous, pale, and soft; they may not
object to a stallion’s presence and may even
permit mounting, but intromission is often
prevented by holding their tail down
(Youngquist & Threlfall, 2007). Young mares
have been shown to begin anestrus earlier
than mature mares. Most sheep are
seasonally polyestrous and short day
breeders but they enter anestrus if
pregnancy is not established during the
breeding season (Frandson et al, 2009).
Animals that undergo seasonal anestrus
prevent parturition when the survival rate of
the fetous would not be high in the
environment.
Sows and cow exhibit lactational anestrus in
which prolactin during suckling inhibits
GnRH release causing anestrus. Lactation in
sows completely suppress estrus while in
cow suppress for up to 60 days.
Anestrus which occur during gestational
period is called gestational anestrus. The
progestorene in gestational period has a
negative feedback to GnRH hence anestrus.
This type of anestrus is useful to allow
uterine involution prior to the first post-
partum estrus cycle. Energy imbalance
inhibit GnRH pulse hence triggers nutritional
anestrus. It mostly occurs in primaparous
female animals.
CONCLUSION.
All in All, anestrus is a state when a female is
not exhibiting normal estrus cycles. Anestrus
can be normal or pathological. Seasonal
anestrus contribute to a major adaptability
and survival rate of conceived fetuses.

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LITERATURE REVIEW OF ANESTRUS IN BITCHES AND OTHER DOMESTIC ANIMALS.
REFERENCES
i. Cupps,T.P.(1991).Reproduction in
Domestic Animals.4th Edition.
Academic Press,Inc. New York.
ii. Frandson,R.D.,Wilke,W.L.,and
Fails,A.D.(2009).Anatomy and
Physiology of Farm Animals.7th
Edition.Wiley-Blackwell.
iii. Hafes.E.S.E.(1993).Reproduction in
Farm Animals.6th Edition. Lea and
Febiger. Philaphedia.
iv. Youngquist,R.S.,and Threlfall,W.R.
(2007).Large Animal
Theriogenology.2nd Edition. Saunders
Elsevier,Inc.St Louis,Missouri 63146.