Farm Animal Reproduction

 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

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. 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

 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

 Anterior pituitary
- In response to FSHRH releases FSH ( follicle
stimulating hormone)
- FSH acts on the ovary

 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

 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)

 Anterior pituitary
- Releases LH in response to GNRH
- LH causes the follicle to rupture leading to
ovulation

 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)

 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

 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)

 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

 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

 Diffuse placenta- in horse and pig
 Cotyledonary placenta – in ruminants
 Zonary placenta- in dogs and cats
 Discoid placenta- in humans and monkeys

 Follicle stimulating hormone ( FSH) – follicle
development/maturation
 Luteinizing hormone (LH)- ovulation
 Estrogen- behavioral signs of estrus, psychic
heat, attracting male, accepting male
 Progesterone- prevents ovulation/maintains
pregnancy
 Oxytocin- uterine contractions, milk letdown

 Bovine
- Polyestrus all year long
- Beef cattle spring calving, minimizes labor
costs
- Dairy cattle, year round calving for milk
production

 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

 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

 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

 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

 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

 Increased breedings per ejaculate
 Semen extender used
 Disease control
 Trained personel required
 Males do not need to be maintained on farm

 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

 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

 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

 Overall physical condition
 Breeding history
 Semen analysis
 Semen collection
 Scrotal circumference
 Libido/reproductive behavior

 Overall physical condition
 Breeding history
 Rectal palpation
 Ultrasound
 Uterine culture
 Uterine biopsy
 Endoscopic exam of uterus
 Serum hormone assays

 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

 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

 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

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

 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

 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

 Factors affecting risk of dystocia
- Abnormal presentation
- Multiple births
- Heifer vs cow
- Pelvic measurement
- Nutritional status- obesity/malnutrition

 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

 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

 Vaginal/uterine prolapse
 Obturator paralysis
 Milk fever/hypocalcemic tetany
 Rejection of offspring

 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

- 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.

- 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)

 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

 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

 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

 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

 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%

 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

 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.

 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

- Tube feeding for foals lacking sucking reflex
- Esophageal feeder for calves/lambs/kids
- Transfer of neonate to foster dam

 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

 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

Farm Animal Reproduction

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Farm Animal Reproduction