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About 16 to 18 days after a heat
period under the influence of GnRH the pituitary produce FSH this is released
into the blood stream. FSH causes development of follicle of ovary. The
follicle in turn over a 3 to 5 days period produces estrogen as it grows in
size. Estrogen level peaks at 19 to 20 days. Estrogen causes following changes
in cow.
Physical:
Increase of blood lining of the uterus
Thickening of wall of vagina
Increase growth of cell and cilia in oviduct
Relaxation of cervix
Mucus production by cells of cervix
Mucus is usually thick and milky in color
Decline of previous CL on ovary
Behavioral:
Late in this period, the female animal usually
exhibits interest in the male
Hormonal:
High estrogen level cause production of LH about
day 20.
Estrus Phase:
FSH and LH affect the ovary to
stimulate follicle rupture and release of the egg contained within. Physically
this period is characterized by sexual desire and acceptance of male. Estrogen
continues to dominate the reproductive tract and produce the following changes.
Physical:
Engorgement of the uterus wall
Contraction of oviduct
Relaxation of cervix
Mucus secretion is clear, transparent and
stringy
Vulva is swollen and relaxed
Ovulation occurs after 12 hours after the end of
this period
Behavioral:
Effects of estrogen of CNS produce the
characteristic behavioral pattern of reception of male
Met estrus phase:
This stage last for 3 to 4 days,
the same length of time it takes the ova to reach the uterus. The egg is picked
up by the oviduct, and the follicle collapses. LH causes the production of a
new cell type, the luteal cell in the ruptured cell, in the ruptured follicle.
This gives rise 1st to the Corpus hemorrhagicum where the blood
invades the follicular space and then the Corpus luteum which produces
progesterone which changes the state of reproductive tract.
Progesterone prevents the FSH
secretion and therefore prevents the further development of follicles.
Physical Change:
Blood discharge occurs about 2 days after
estrous in 50 to 80% of all cows. This blood does not indicate ovulation or
success or failure of the breeding; but, it indicates some hemorrhage of the
uterus lining
Mucus secretions decrease
The uterus becomes soft, pliable and relaxed
Uterus wall grows thicker in preparation for
pregnancy
Cervix begins to close
Diestrus Phase:
This is the longest period in the
estrus cycle, generally lasting from day 4 to 18
The Corpus luteum matures and
produces progesterone with the influence of reproductive tract.
Physical Change:
Thickening of uterine lining
Cervix closes
Vaginal mucus is scant and sticky
Uterus muscles are relaxed
If the egg is not fertilized in
the oviduct, the CL grows for 10 to 12 days. If no embryo is present, high
progesterone level causes production of PGF 2a. Prostaglandin influences the
ovary and causes degeneration of CL and therefore, a decrease in progesterone.
This leads to FSH production and re entry into the proestrus phase with the
development of a new follicle. This normal cyclic activity repeats itself
If the egg is fertilized, the CL
body continues to produce progesterone. The recognition of an embryo by the dam
blocks the release of PGF2a. Progesterone relaxes the uterine muscle and
encourages growth of uterine lining to nourish the fertilized egg. Progesterone
production by the CL is important for maintainace of pregnancy during the 1st
2/3 of gestation. After that progesterone is produced by the cells of the
placenta and adrenal glands.
STAGES LEADING TO
FERTILIZATION:
Ovulation and insemination
Transport of ova and sperm
Capacitation of sperm
Activation of egg
Formation of zygote
1: Ovulation and Insemination:
Towards the end of the estrus period,
the cow becomes receptive to the male. The follicle ruptures and the ova or egg
travels into the oviduct or fallopian tube. In natural services sperm is
deposited in the anterior vagina next to the cervix. In artificial
insemination, the sperm is deposited within the cervix or just inside the
uterus.
2: Transport of Ova and Sperm:
The hormonal changes of the estrus cycle are
very important in changing of the reproductive environment to facilitate ova
and sperm transport. The oviduct experience contractions. Hair like cilia on
the inside the oviduct creates waves in the oviduct fluid and assist in ova
transport.
The sperm moves rapidly through
the uterus to the upper 1/3 of the oviduct where fertilization occurs
The egg is fertile for
approximately 10 to 12 hours. If fertilization occurs after this time, an
abnormal embryo results. This may lead to and early embryonic death or early
abortion
3: Capacitation of Sperm:
For fertilization to occur, a
process known as capacitation must 1st occurs. Cpacitation refers to
the functional change in the head of the sperm which then allows it to
penetrate the cells of the ova
4: Activation of Egg:
Once the sperm has penetrated the
egg, a reaction occurs preventing penetration of further sperm. Male and female
pro nuclei form, a mixing of the chromosomes occurs and the union forms the
zygote
5: Fertilization:
Once the fertilized ova has
formed the cells within divide. The ova goes through 2/4/8/16/32 cell stages.
Fertilized ova usually enter the uterus from the oviduct, about 4 days after
estrus.
Important times to remember:
Fertile life of egg is 10 to 12 hour after ovulation
Time required for capacitation of sperm is 4 to 6
hours
Life time of sperm is 24 hours
Transit of fertilized ova from oviduct to uterus is
day 4
If insemination occurs too early, the sperm may have
died prior to ovulation
If insemination occurs too late the ova has passed
its fertile life period before the sperm gains the ability to fertile the
egg
In general cows noticed in heat in the morning should
be bred later the same day. Cows noticed in heat in the after noon should
be bred next morning
Physiology of female reproductive Organs:
1: Reproduction,
Sexual maturity and breed maturity:
Puberty is the period of a cow’s
life when it is able to release ova and to manifest complete sexual behavior sequence.
Puberty is basically the result of a gradual adjustment between increasing
sexual hormonal activities from the pituitary and the ovaries.
At puberty in heifers there is an
increase in ovarian size due the presence of follicle. This is associated with
the ability of follicles to ovulate as a consequence of LH peak, a hormone
secreted by pituitary for ovulation. The time of onset of this activity appears
to be a function more of the weight than age of the animal. Restricted
nutrition delays puberty in cattle.
Dairy cattle reach puberty when
its body weight is 30 to 40% that of their adult weight whereas in beef cattle
this percentage is higher. Generally speaking in normal conditions, puberty
occurs between 300 to 360 days of age in dairy cattle and between 320-460 days
of age for beef breeds.
2: Sexual
or Heat cycle:
The estrus cycle is divided into
four arbitrary stages:
Proestrus
Estrus
Metestrus
Diestrus
Each stage is controlled by
reproductive hormones produced by the nervous system and by ovaries and uterus.
3: Cycles
of Ovary
Oogenesis is defined as formation
of primordial follicle. The ovary of a newborn calf contains several hundred
and thousands oocytes. Only a small percentage is ovulated during the life. The
primordial follicle forms preovulatory Graffialn follicle. The mature follicle
extends through thickness and protrudes above the ovarian surface like a
blister.
The active follicle produces the
hormones called estrogen mainly responsible for estrus signs
Ovulation is the rupture of the
Graffian follicle and release of mature oocyst. The oocyst is then called ovum.
Present evidence shows that high level of LH stimulates the plasminogin and
collaginase in the follicular wall that will participate in the digestion of
intercellular connective tissue. This will result in release of the ovum.
After ovulation the follicular
cavity fills with blood forming a corpus hemorrhagicum. The granuloseand thical
cells enlarge to fill the follicular cavity. The corpus luteum is highly
vascularized. This process is called lutinization. CL produces progesterone
that inhibits estrus behavior.
4: Cycles
of the Uterus:
During the follicular phase of
estrus cycle, the vascularity of the uterus is increased due to estrogenic
stimulation. The uterus becomes engorged with blood, especially in the
carouncular area. It is firm and turgid
At this stage the mucus cells of
the cervix are stimulated and thin watery mucus is discharged from the cervix
and expelled from the vagina. The glands in the vagina are also stimulated to
secrete mucus. The increase in blood circulation in vaginal wall will induce
slight edema.
5: The
Oestrual Cycle:
In cows the estrus cycle lasts 20
to 21 days. An open cow will continue to start a new reproductive cycle until
it is bred and become pregnant. Cycle can range in length from 18 to 24 days.
The cycle can be divided into 2 phases
Follicular
Luteal
The 1st day a cow is
in heat is called day zero of the cycle. The follicular phase is ended by the
ovulation of a mature oocyst. After ovulation follicular cell are transformed
into the CL. This is the beginning of the luteal phase. The end of the luteal phase
begins with luteolysis, the destruction of CL to allow rapid growth of the new
ovulatory follicle
6: Hormones
of Reproduction:
Hormones are chemical agent
synthesized and secreted by specialized glands and carried by the blood to
other parts of the body where they act on specific tissues or organs
In cow reproduction we are
primarily concerned with three different types of hormones.
Releasing hormones
Gonadotropic hormones
Sex steroid hormones
Releasing hormones originate from the hypothalamus and control the
synthesis and release of hormone from the anterior portion of the pituitary
gland. The hypothalamus is part of the brain.
The gonadotropic hormones produced in the pituitary are directly
involved in maturation and release of ova. They also stimulate the secretion of
sex steroids hormones from the ovary. The pituitary gland is located in a
pocket beneath the brain to which it is connected by the pedicle of nervous and
blood vessels.
The sex steroid hormones are involved in the behavioral aspects of
reproduction, in development and maintainace of secondary sex characteristics
in maintainace of reproductive organs and in regulation of reproductive cycle
and pregnancy.
HORMONE
ORIGIN
FUNCTION
GnRH
Hypothalamus
Stimulation and
release of FSH and LH
FSH
Pituitary gland
Follicular growth
and production
LH
Pituitary gland
Final maturation of
follicle, ovulation, CL formation
Estrogen
Ovary (Follicle)
Growth of uterus ,
estrus behavior, cervical mucus secretion, release of LH for ovulation
Progesterone
Ovary (CL)
Maintains
pregnancy, keeps cow from cycling
Oxytocin
Ovary (CL),
Pituitary
Milk excretion and
prostaglandin synthesis
PGF2A
Uterus
Lysis of CL
7: Control
of Sexual Cycle:
GnRH from hypothalamus cuase
release of FSH from the pituitary gland. The FSH reaches the ovaries by blood
circulation and stimulates the development of follicles.
The follicles in the ovaries
produce esterdiol which brings the cow in estrus. One follicle produces more
esterdiol than the others on the ovaries and grows more rapidly.
The level of esterdiol in the
blood rises causing a greater discharge of GnRH by the hypothalamus. The
pituitary then release less FSH. The level of esterdiol causes the pituitary
gland to secrete a massive discharge of LH in response to frequent stimulation
by GnRH. This provokes around 36 hours after the LH spike, the final maturation
of the follicle which ruptures to expel the ova. Under the stimulates of LH the
follicle cell transform into luteal cells to form CL. The CL progressively produces
progesterone. CL reaches at its maximum size at day 11-13.
If pregnancy does not occur at
day 16-17 CL begins to regress due to production of oxytocin produced by the CL
cells and the luteolytic PGF2a secreted by the uterus.
If pregnancy occurs the CL
remains and continues to produce progesterone until the birth of the calf.
PRIMARY EXAMINATIONS
1: Pre-Insemination checks:
Restrain the cow or heifer but do not tie down or
over excite
Identify the cow to be inseminated.
Approach the cow slowly, talk to her, do not rush, do
nothing to excite her
Check for previous services and
in case of repeats, note observations such as late repeats over 23 days, early
and quick repeats less than 17 days and watch for possible pregnancy
2: Heat
Signs:
Coming into heat
Standing heat
Going out of heat
Appetite
Noticeable decrease
Sharp decrease
Slowly returning
Nervous behavior
Very noticeable
Very noticeable
Noticeable
Fence walking
Very noticeable
Very noticeable
Noticeable
Bawling
Frequent
Less frequent
Frequent
Persistent trailing of other
animal
Yes
Yes
Very little
Temperament towards other
animal
Very antagonistic
Less antagonistic
Back to normal
Head butting
Quite frequent
less frequent
Frequent
Licking other animal
Yes
Yes
Yes
Mounting behavior
Will jump others but will not
stand to be ridden
Will jump on others and will
stand to be ridden
May jump others but not stand
to be ridden
Response to observe
Cautions
Interested
Shy, avoid
Mucus present
Occasionally
May occur frequent
More frequent
Mucus consistency
Watery
Cohesive strand
Cohesive strands
Vulva
Red and puffy
Red and puffy
Less swollen
Bloody discharge
Not usual
Not usual
May present
3: General conditions of the Animal:
Cow should be in good physical condition. Cows
gaining body weight conceive better than cows in a weight loss condition
Observe for abnormal discharge from vulva. They are
signs of infections and need to be treated before breeding
Observe for bloody discharge. It may be to late to
bred
4: Insemination Procedure:
All insemination equipments and
supplies must be clean and sanitary. Use disposable equipments only once. Be
extremely careful when handling the insemination gun, sheath and straw of semen
to keep them clean and free from contamination
Summary in points form describing
the step by step procedure eh inseminating the cow:
Have a thawing thermos prepared with the proper
temperature of water, 37C
Place insemination kit close to liquid nitrogen semen
tanks.
In case of repeats, note if the animal in question is
a late repeat or is she early or quick repeat. Watch for possible signs of
pregnancy when examining the cow prior to insemination.
Remove the lid and place it in a clean area
Prior to lifting any conister from your liquid
nitrogen tank, assure yourself of the semen location
Lift conister high enough to reach the cane
containing the dose of semen. Be assure not to lift the consiter above the
frost line in the neck of your tank
Identify and remove dose as quickly as possible from
the tank. The recommended time is between 15 to 1 minutes
In order to reduce the chance of straw exploding
after they were removed from the nitrogen tank, immediately and without
hesitation shake the straw in a short swing movement similar to that of
nurse shaking thermometer. This will remove small drops of nitrogen which
may be trapped at one end of the straw. The plug is needed to expel the
semen form the straw
After this now load the gun properly
Approach the cow slowly and gently and talk to her
Lubricate your gloved hand with mineral oil; rub
gently the anal area of the cow. This will relax the animal and make the
entry of your hand into the rectum easier
With your four finger and thumb, a wedge is formed
which in turn slowly and firmly pushed into the rectum of the cow
Gently massage the rectum and examine the
reproductive organ. Note the abnormalities
Pull your hand back towards vulva. Now you are in position
to clean the vulva with the clean, dry paper towel. Do this 2 to 3 times
if necessary. Use a new towel each time. Remove as much manure as you can.
Now gently aside the vulvular lips for clean entry.
The inseminator should not touch the outer lips of vulva while he is
carefully inserting the insemination device into the vagina
Be sure to insert the insemination device into the
vagina at a 45 angle to avoid entry into urethral opening
After the insemination device has been manipulated
into the body of uterus the semen may now expelled from the insemination
device. Push the plunger very slowly. It is advisable to count backwards
from 10 to zero.
In order to prevent injury to the reproductive tract
remove the insemination instrument very slowly
Remove arm form rectum slowly
Dispose the dirty glove and sheath
Before going to next case make sure your equipment is
clean and free from manure
It is a good practice to remove all of your
equipments from your kit and clean it thoroughly once a week
Thawing
Frozen Semen:
Since the discovery of frozen
semen technique by Dr. Chris Polge in 1949, thawing procedure for frozen semen has
changed dramatically since that time.
The volume of semen dose for each
insemination has also been changed from origin 1 ml ampoule to the present 0.5
and 0.25 ml straws. The volume and surface relationship of each packaging
system influences the thawing rate of spermatozoa.
Following are the most commonly
used semen packages system throughout the world.
1 ml ampoule
0.5 ml
0.25 ml ampoule
Insemination
Technique:
One should pay special attention that 1/3 of the
insemination device which is entering the animal be clean.
Injuring the animal with the insemination pipette
can cause failure of conception
An injury to mucus membrane can cause bleeding.
This blood is harmful to semen, and fertilization may not occur, because
the sperm cells agglutinate. Even if the fertilization has taken place
the fertilized embryo may be unable to implant in the lining of uterus
causing an early embryonic death.
In order to prevent the injury to the rectum of the
animal the inseminator should have great care to always trim the nail.
Most common error
during insemination
Fundamentals when using semen stored in the liquid nitrogen.
The development and use of frozen semen stored in the liquid nitrogen and
especially the reduction of semen packages to 0.5 to 0.25 ml respectively
requires special training and careful handling of these packages
The operator must e precise and gentle as well as
technically competent to introduce the semen into the animal. The insemination
equipments for the straw should be thin and rigid. The insemination should not
be performed roughly.
Errors when animal
are not restrained:
A high degree of injury to the rectum of the reproductive
tract can occur
And exact, careful and smooth introduction of the
insemination equipments is difficult
Inseminator is at great risk of injury
Deficient
Hygiene:
1: Rough and
Uncontrolled Insemination technique:
Injuring the animal with the
insemination pipette can cause failure of conception
An injury to mucus membrane can
cause bleeding. This blood is harmful to semen, and fertilization may not
occur, because the sperm cells agglutinate. Even if the fertilization has taken
place the fertilized embryo may be unable to implant in the lining of uterus
causing an early embryonic death.
2: Intra cervical insemination:
This method should be used only
when a cow is not showing clear and distant signs of estrus.It is also advisable to use intracervical
semen deposition if a chance of pregnancy exists. If the tip of the insemination
rod is passed through the cervix into the uterus the animal may abort.
3: Deep intrauterine Deposit:
This type of insemination is to
be avoided. This can cause injury to delicate uterine membrane with
instruments. It is seen that deposition in the uterine body is considerably
superior that other depositions
