Estrous
cycle is recurring period of sexual activity which is accompanied by
maturation of one or more follicles on ovary and terminates with
shedding of one or more ovum. The estrus cycle on an average is 21
days with the range of 18-24 days.
Cycle
is stopped:
-
When female is conceived/ pregnant
-
Any pathological condition
-
Due to unfavourable condition
Estrous
Period:
It is the period during which female shows excitement.
Anestrous:
Lack of cyclicity or estrus. In some spices it is normal due to
physiological changes.
Phases of Estrous Cycle
There
are four phases of Estrous Cycle:
-
Proestrus
-
Metestrus
-
Estrus
-
Diestrus
Stage of cycle |
Buffalo |
Cow |
Estrus cycle (d) |
22-24 |
21 |
Proestrus (d) |
2-3 |
3-4 |
Estrus (hours) |
16-18 |
12-18 |
Metestrus (d) |
2-3 |
3-4 |
Diestrus (d) |
12-16 |
10-14 |
Proestrus:
-
In this period uterus
prepares for estrus
-
There is regression of
CL due to PGF2α and follicle starts growing
-
Tonicity of uterus
increases
-
Secretary activity
increases and reaches its peak on day first of cycle
Estrus:
Estrus is characterized as the time period when the female exhibits
sexual desire and acceptance of the male by standing to be mounted.
Internal Changes:
-
Dilation of cervix (diameter is relatively large, closed cervix
means diameter is relatively small)
-
Uterine tonicity (mild, moderate, or severe)
-
Grafian follicle on ovary (usually one in bovine).
-
Mucous production which is directly related to hormone
(estrogen). It is secreted from secretary cells. So increased
estrogen, increased mucous.
-
Change in color of vagina (hyperemia).
External changes:
-
Vulva is swollen (wrinkles are disappeared)
-
Tonicity is due to increase blood flow to uterus. It is
beneficial. This blood flow to the uterus prevent from
establishing of infection because blood contains macrophages.
-
Uterus
is more prone to infection under the influence of progesterone.
-
If we palpate the ovary, follicle becomes thin and thin as it
moves toward the end of estrus.
-
Estrus is only visible phase during which we see the changes in
the behavior of animal. Estrus period and signs of estrus are
quite variable in bovines. In buffalos it is difficult to detect
estrus as they show silent estrus. Buffalos have nocturnal
behavior. They are active in night specially late night due to
low temperature.
Primary Signs of Estrus:
Stand to be mounted, bellowing, restlessness, swollen and reddish
vulva, mucous discharge.
Secondary Signs of Estrus:
Increased urination, low
feed intake, rough hair on back and tail, isolation from other
animals, low milk production
Metestrus:
-
Period following the
estrus is called metestrus.
-
During this period
ovulation occurs and ovulation fossa or depression is formed on
grafian follicle
-
This depression is
gradually filled up by granulosa cells which transfer into
luteial cells and later grafian follicle is transformed into
carpus luteum (CL). CL is palpatable at 5th day which is soft,
conical and reddish in colour.
-
Aggressiveness decreases
-
Tonicity in uterus
gradually decreases
-
Mucous secretion is also
decreased due to decrease in estrogen because it is directly
proportional to the estrogen.
-
Externally wrinkles are
appeared on vulva.
-
Color of vagina changes
from hyperemic to pale.
-
Animal is reluctant to
accept male.
Diestrous:
-
It is longest period of
cycle.
-
Animal is silent or
quiescent.
-
During diestrus CL
further grows and become mature on day 9th. A mature CL has
depression in centre. Mature CL remains upto 16 day.
-
During this phase there
is dominance of progesterone.
-
Organs are flaccid. No
tone at all.
-
One follicle matures at
11th day which is called midcycle follicle. At 10th and 11th day
we find both structures; CL and mature follicle (mid cycle
follicle). Mid cycle follicle subsides and becomes atretic
follicle within next one or two days called follicle atrasia.
-
On 17th day regression
of CL starts.
Gestational estrus:
During
pregnancy signs of estrus are shown by buffalo. It is about 5 % and
generally occurs at 5th month of pregnancy due to change in hormone.
It is known as gestational estrus. This function is performed by
placenta.
Signs of Estrus in Rectal Palpation
Proestrus:
o
Slight tonicity of uterus
o
Vulva is slightly swollen
o
Vulva is pink to red
o
Follicle on ovary
Estrus:
o
Graphian follicle
o
Increase in tonicity of uterus
o
Relaxation of cervix
o
Follicle is like blister
Metestrus:
o
Ovulation fossa on ovary
o
Decrease in tonicity
o
Post estrus bleeding in cows
Diestrus:
o
Corpus luteum (liver like)
o
Flaccid horns, uterus
o
Animal shows resistance for palpation
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