The document discusses the estrous cycle in various species, including the hormonal control of estrus and ovulation. It also covers signs of impending parturition, stages of labor, common dystocia issues, care of the newborn including colostrum administration and management of failure of passive transfer. Reproductive techniques like estrus synchronization, artificial insemination, and embryo transfer are also outlined.
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The Female Reproductive Cycle: Stages of Estrus and the Hormonal Control of Ovulation
1.
2. Consists of
proestrus, estrus, metestrus, diestrus and
anestrus
1. proestrus- begins after corpus luteum
regression, ends at the onset of estrus. During this
period there is rapid development of the follicle
which leads to ovulation and the onset of sexual
receptivity
3. 2. estrus- time of sexual receptivity, may be
referred to as heat. Ovulation usually, but not
always, occurs at the end of estrus.
- Some species, like cats and ferrets, are induced
ovulators
3. metestrus- the early postovulatory period
during which the corpus luteum begins
development
4. 4. diestrus- the period of mature luteal activity
which begins about 4 days after ovulation end
ends with regression of the corpus lutem.
5. Anestrus- without estrus cycles
5. Hypothalamus
- Located in center of brain, next to pituitary
gland. Considered a master gland that controls
the pituitary gland
- Releases FSHRH ( follicle stimulating hormone
releasing hormone) which acts on the anterior
pituitary
6. Anterior pituitary
- In response to FSHRH releases FSH ( follicle
stimulating hormone)
- FSH acts on the ovary
7. Ovary
- In response to FSH it begins to develop a
follicle
- Follicle is like a small blister on the ovary and
contains a maturing egg
- Follicle produces estrogen which causes the
animal to come in heat ( estrus)
- Estrus in cows is about 18 hours
8. Hypothalamus
- Produces GNRH gonadotropin releasing
hormone when estrogen has been present for a
sufficient amount of time
- Causes the anterior pituitary to release
leutenizing hormone ( LH)
9. Anterior pituitary
- Releases LH in response to GNRH
- LH causes the follicle to rupture leading to
ovulation
10. Ovary
- Rupturing of the follicle occurs with low estrogen
and high leutenizing hormone
- Egg released into the oviduct ( occurs 12-24 horus
after estrus in cow)
- Menstrual bleeding may occur but not in every
estrus
- Corpus luteum is formed out of the remaining
follicle
- Most successful artificial insemination is done 12
hours after the beginning of estrus ( so
insemination precedes ovulation)
11. Corpus luteum
- Yellow body made up of remaining follicle
tissue
- Formation is initiated by the LH surge
- Produces progesterone which maintains the
lining of the uterus for possible implantation
- If implantation occurs the placenta in the cow
will continue to produce progesterone to
maintain the pregnancy until birth
12. Not pregnant
- The corpus luteum only lasts about 3 weeks so
if implantation does not occur, the lining of the
uterus will be sloughed and replaced
- The uterus will produce prostaglandins if not
pregnant ( help the uterus to contract)
13. Ovary ( if not pregnant)
- The prostaglandins produced by the uterus if
not pregnant ( 14 days after ovulation) will
travel to the ovary and cause lutealysis
- The corpus luteum will be destroyed which
will drop the progesterone level
- The dropping of the progesterone level will let
the animal come back into estrus
14. Pregnant animal
- First the corpus luteum secretes progesterone
and continues to do so throughout most of the
pregnancy
- Then the placenta takes over to maintain
pregnancy
- Implantation takes 5 weeks in cattle and horses
15. Diffuse placenta- in horse and pig
Cotyledonary placenta – in ruminants
Zonary placenta- in dogs and cats
Discoid placenta- in humans and monkeys
17. Bovine
- Polyestrus all year long
- Beef cattle spring calving, minimizes labor
costs
- Dairy cattle, year round calving for milk
production
18. Equine
- Seasonally polyestrus in spring and summer
- Ovarian activity increases with increased day
length
- Ovarian activity can be induced/manipulated
with artifical lighting
Porcine- polyestrus all year long
Ovine/caprine- polyestrus fall/winter
19. Vaginal discharge, blood tinged or otherwise is
not associated with estrus
14-28 day estrous cycle with 21 days being the
average
Length of estrus ranges from 6-24 hours with
the average being 15 hours
Time of ovulation is 24-32 hours after onset of
estrus
20. Proestrus cows will mount estrus cows
Gomer bulls ( penis surgically redirected out of
lateral aspect of prepuce to prevent breeding)
will detect females in estrus
21. Prostaglanding F2 alpha- lyses corpus luteum
to bring animal into estrus
Progestogen ( regumate) synthetic
progesterone- suppresses ovaries, prevents
estrus, aids in pregnancy maintenance
Human chorionic gonadotropin, comparable to
LH to induce ovulation
Oxytocin- induce labor
Dexamethasone- induction of labor
Artificial light- alteration of day length
22. Natural cover
- Male and female must be present and capable
of breeding
- Limits potential progeny
- Risk of physical injury to male or female
Pasture breeding
Hand breeding
23. Increased breedings per ejaculate
Semen extender used
Disease control
Trained personel required
Males do not need to be maintained on farm
24. Allows multiple pregnancies per breeding
season
Successful reproduction of physically
compromised animals
Donor female can still compete
Recipient dam just carries the baby, shares no
genetic material with fetus
Used to create number of genetically similar
individuals
25. Estrus synchronization of donor and recipients
Superovulation of donor by FSH
administration 40 hours prior to estrus
Insemination hand breeding or artificial
insemination
Embryo collection established post
insemination
26. Balloon catheter established proximal to cervix
1-2 liters of buffered saline infused into cervix
Gravity used to recover saline and embryos
Embryos caught by in line filter
Embryo evaluation/processing
Embryo delivery to recipient dam
29. Failure to return to estrus
Rectal palpation early in cow by palpating a CL
or enlarged uterine horn at 30-45 days
Doppler Ultrasound, transrectal ultrasound
Progesterone levels in blood and milk
At 3 months, increase in blood flow in uterine
artery is felt as a buzz
Ballottment- pressure on lower right
abdominal wall with fist or knee and lifts fetus,
feel it kick back into place
30. Early pregnancy diagnosis 14-15 days
Twin reduction <18 days
Fetal sex determination 65 days
Gestation period in bovine is 280-290 days with
some breed variation
31. Signs of impending parturition
- Relaxation of tail head muscles
- Relaxing /Lengthening of vulva
- Waxing of teats- yellow tinged colostrum,
extended/excessive dripping may result in
insufficient colostrum available for newborn
32. Stage 1 labor- may be interrupted several times
without injury to fetus
Stage 2- duration one hour
- Rupture of placental membranes, water
breaking, may look like urination
- Vaginal exam is performed 5-10 minutes after
onset of stage 2 labor to assess fetal
presentation, cervical dilation
Stage 3- placenta delivered
33. Presentation of fetus- forelegs first ( breech
birth, hindlegs first, is normal presentation in
goats, swine and sheep)
Most cows and mares will lie down prior to
expelling calf/foal, if traction is required for
delivery, attendant pulls down- toward the
dams hocks, not straight out, parallel with the
spine
34. Allow neonate to rest with hindlegs still in
vaginal canal if the umbilical cord is intact. Up
to 1 liter of blood may be transferred from the
placenta to offspring
Neonate should be standing, ambulatory and
nursing within one hour after birth
Expulsion of placental/fetal membranes (
afterbirth) cleaning should occur within several
hours of birth. Membranes that are not
completely passed within 8-12 hours represent
a medical emergency; retained placenta
36. Repulsion then traction
Pubic symphysiotomy- in first calf heifers, if
calfs head is larger than the pelvic canal the
veterinarian can open and spread the suture
between the pubic bones thus enlarging the
pelvic canal diameter
Cesarean section
Fetotomy- if fetus is dead, dismembered and
delivered in pieces. Note: care must be taken to
avoid sharp bone pieces piercing/rupturing
uterine wall
37. Examine vagina, vulva and perineal body for
injury
Examine afterbirth for completeness
Examine mammary glands, express colostrum
for evaluation
Monitor abdominal discomfort, mm
Monitor maternal behavior, interaction with
newborn
39. Colostrum
- Requirement – 1 liter per 100 lbs
- Colostrum banking- dams will produce more
colostrum than needed. After neonate has
consumed a sufficient amount, the rest may be
milked out and frozen for storage for up to 1
year
40. - Colostrum quality- ( quality =
immunoglobulin content)
a. subjective- stickiness, thickness (Note: color is
not a reliable criteria for assessing quality)
b. Objective- specific gravity > 1.060
- Gut closure- the neonatal intestinal tract has the
transient capability to absorb large (
immunoglobulins) molecules intact. That
capability is lost after 24 hours or the consumption
of 32 ounces of material. Colostrum consumed
after gut closure is of no benefit.
41. - behavior- strong suck reflex
- Umbilicus- iodine ( foals apply every 12 hours
until navel remains dry)
- Meconium- feces that accumulates in the colon
during fetal development, can be rock hard and
difficult to pass. If straining is observed,
administer phosphate enemas until meconium
is passed. ( colostrum has laxative)
42. Distress, lack of vigor, cyanosis
Aspiration of amniotic fluid- breech
birth/dystocia- hold foal/calf upside down to
clear airway of fluid before initiating CPR
a. A- airway, establish patent airway first
b. B- breathing, dopram may be administered to
stimulate respiration
c. C circulation- cardiac
compressions, resuscitation
43. Failure of Passive Transfer- absence or
decreased levels of circulating IgG ( of
maternal origin, neonate cannot produce its
own IgG until 3-4 months of age)
a. IgG <200 mg/dl is complete failure
b. IgG200-400 mg/dl- is partial failure
c. IgG > 400 is adequate passive transfer
44. Mare origin failure of passive transfer
- Loss prior to foaling ( leaking)
- Poor quality ( low levels of immunoglobulins
in colostrum)
- Failure to produce colostrum, neonates born
before reaching term
45. Foal origin failure of passive transfer
- Inadequate colostrum
- Gut closure
Treatment
- Administer colostrum or plasma orally if FPT is
diagnosed before gut closure
- Administer plasma intravenously if FPT is
diagnosed after gut closure
46. Maternal antibodies in colostrum destroy foals
RBC’s
- Does not occur in primiparous, first foal mares
- Symptoms: anemia, icterus, hemoglobinuria
- Prevention: agglutination test prior to allowing
foal to nurse
- Agglutination test- foals RBC’s mixed with
graded dilutions of colostrum, evaluated for
agglutination
- TX: transfusion if HCT < 15%
47. Dummy foal syndrome
Suck reflex absent and may take 30+ days to
resolve
High risk foal-failure of passive transfer or
neonatal septicemia
Guarded prognosis
48. Neonate should consume 10% of body weight
per day in milk or milk replacer
Foals: typical nursing pattern of once per hour
consuming 90 ml per feeding
Note: mare goes into heat 5-7 days post foaling.
Hormones passed in milk result in diarrhea of
foal ( foal heat diarrhea). This diarrhea rarely
requires medical intervention and
spontaneously resolves when mare goes out of
heat.
49. Orphan animal/animals unable to nurse on
dam
a. Bottle feeding- healthy animals with normal
suck reflex
b. Bucket feeding
- Much easier than bottle feeding
- Orphans should be trained to bucket asap to
minimize labor costs and decrease aberrant
behavior associated with hand raised animals
50. - Tube feeding for foals lacking sucking reflex
- Esophageal feeder for calves/lambs/kids
- Transfer of neonate to foster dam
51. Deworming- typically begins at the same time
as initial vaccination series
Vaccinations not performed until maternal
antibody levels decrease
- Foals: 4 months
- Calves: 6 months
- Sheep/goats- 2 months
- Pigs- 3 weeks
52. Social behavior
1. Imprinting
- Training to accept procedures that will be
performed later in life
- Bonding with dam/other animals/humans
2. Provide companion if dam is unavailable,
alternate species is acceptable