parturition module ans 536 spring 2015. we need to be able to picture what is going on on the inside...
TRANSCRIPT
We need to be able to picture what is going on on the inside by what we see on the outside…
Do not intervene the process unless absolutely necessary
Humans Gestation length: 280 days
Cattle Gestation length: 283 days
Swine Gestation length: 114 days
During Gestation: Progesterone levels remain high
Keeps uterus in a stage of inactivity (“dormant”) Maintains pregnancy
Humans Human chorionic gonadotropin (hCG) responsible for maintaining
corpus luteum (CL) CL produces progesterone
Third Trimester = “late gestation” Uterus becomes more excitable Hormone levels change
Before Parturition, Focus on Environment
Keep the pen clean, dry and well ventilated Swine: The farrowing pen temperature should be approximately 20 ̊C and the piglets’ nest area, 30 to 32 C̊
Canadian studies in 2002 reported a 20% reduction in piglet mortality when a second heat lamp behind the sow provided a zone at 31 C̊ during farrowing.
Cleanliness of stall and perineal region of mother is KEY to keeping neonate healthy
Prevents sepsis, umbilical infection If not, increased exposure to any fecal- orally transmitted pathogens=
increase in mortality
Hormonal Mechanisms Controlling Parturition In general, these physiological events occur
during parturition:Dilation of cervixContractions of the uterusProgesterone levels decreaseCL and placenta increase production of relaxin
Hormonal Mechanisms Controlling Parturition Cattle
Nearing term Pressure within the uterus causes stress on the fetus,
stimulating the release of fetal cortisol Estradiol increases
Stimulates vaginal and cervical mucous secretion Prostaglandin increases
Contraction of the uterus Oxytocin production
Caused by increased pressure on the cervix, further increases contractions
Relaxin production Relaxes pelvic ligaments
Hormonal Mechanisms Controlling Parturition Cattle cont…
Muscular contractions continue to increase Pressure causes membrane rupture
Fetus begins to move into the birth canalFetus becomes hypoxic
Increases fetal movement Increased muscle contraction and expulsion of
fetus
Hormonal Mechanisms Controlling Parturition Sows…
Parturition is initiated by increased cortisol levels, which also stimulate release of prostaglandin (PG) F2α from the uterus.
PGF2α causes luteolysis of the corpora lutea and release of relaxin.
Oxytocin is released from the pituitary gland, which causes uterine contractions and onset of labor.
Process of Parturition
Three separate stagesStage 1: Cervical dilationStage 2: Delivery of the fetusStage 3: Expulsion of the placenta
Process of Parturition Stage I – Uterine contractions:
Myometrial ischemia: decreased blood flow to myometrium of uterus
Causes release of potassium, bradykinin, histamin, serotonin
Cervical dilation Cervical opening expands to a maximum of 10 cm Longest stage of labor
Lasting a few hours up to 24 hours Cervix dilates with increased pressure from the fetus
Normal presentation – fetal head applies pressure Fetal head is the largest circumference among the body besides
shoulders Abnormal presentation – pressure on cervix may not be as great to
promote maximum cervical dilation needed for fetal passage- can lead to dystocia
Process of Parturition Stage II – Delivery of the fetus
Occurs once cervical dilation is complete Fetus is able to pass through cervix and vagina Fetal passage triggers stretch receptors in the vagina
activating a neural reflex Triggering contraction of the abdominal wall in synchrony
with uterine contractions Increased force pushes fetus through birth canal Additional voluntary force via abdominal muscle
Complete passage through the canal Fetus is still attached via umbilical cord Umbilical cord is severed after complete delivery
https://www.youtube.com/watch?v=lN4DTps8Iuo
Sows or other litter-bearing species.. Piglets are usually delivered at frequent
intervals (10–15 min; 5–45 min range). Uterine horn evacuation is random.
https://www.youtube.com/watch?v=iN4lKCiOGVE
Process of Parturition Stage III – Expulsion of the Placenta
Occurs shortly after delivery Varies among species
Second wave of uterine contractions occur Separate the placenta from the uterus Expelled through the vagina Uterine contractions constrict blood vessels
supplying site of placental attachement Prevent bleeding
Shortest stage of delivery
Dystocia
Noted when difficult, prolonged, or abnormal parturition occursPhysical signs of dystocia:
Cattle: anything other than two front feet showing, ex; only one foot, two rear feet
Lots of blood or meconium in amniotic fluid or on neonate
Neonate has it’s tongue sticking out It is lacking muscle tone, is a color other than pink
Swine.. Incidence of dystocia is low (1–2%) According to the Journal of Swine Health and
Production: Obstetrical intervention is indicated if 30 to 45 minutes have passed since the last piglet was
born if 24 hours have passed since the first signs of
impending parturition were observed and no piglets have been born
if the sow is not able to farrow despite strong uterine contractions.
Dystocia
Contributing factors: Presentation of fetus greatly affects the degree of
dystocia Breech births, etc.
Large birth weight Small maternal pelvic measurements First parity mothers
First-calf beef heifers have 16.7% dystocia vs 2.7% seen in cows
Dystocia Contributing factors cont…
Fetal abnormalities Genetic mutations
Maternal failure to recognize onset of parturition Seen in recipient dams carrying cloned fetuses
Maternal health and/or body condition score Affects the stress and health of fetus Labor may be untimely, too early
Avoiding fetal mortality: Timely recognition of problems Proper assistance in labor process
As with all polytocous species, uterine inertia accounts for most dystocia in swine
Other causes: fetal malposition, obstruction of the birth canal, deviation of the uterus, fetopelvic disproportion, and maternal excitement.
Managing Dystocia Forceps assisted vaginal delivery (humans) Vacuum assisted vaginal delivery (humans) Calf jack to pull calf out of birth canal Cesarean section
Performed often in humans Compromised delivery Mothers can opt for c-sections
Livestock Often used as a last resort
Incurred veterinary cost is high Cause scarring in the uterus
Difficult for the animal to breed back Drugs such as oxytocin, prostaglandin, and corticoids are
administered
Force of Assistance Pulling force should not exceed 150 pounds for Holstein and 75 pounds for
Jersey Assist in dilation prior to pulling (5 minutes) Use appropriate lubricant (not soap and water) Watch your time and assess the calf condition One person pulls with ~100-150 pounds of force Two people pull with ~300 pounds of force 600 pounds of force will fracture femur Calf jack can generate 1500-2000 pounds of force
Apply minimal force during contractions pull calf so head is pushing on the cervix between contractions to speed up cervical dilation
Pull calf straight out until head delivered Deliver shoulders and body at 30 to 400 angle Stop assistance after last rib and allow dam to expel fetus
Assistance prior to full cervical dilation or the use of excessive force is associated with a high incidence of rib fractures (~40%) and a lower incidence of front leg and vertebral fractures (~10%)
Calf Jack and OB Chain Use
https://www.youtube.com/watch?v=_HyApxVijCU calf jack
https://www.youtube.com/watch?v=9aIcnLBXdL0 OB chain placement
Managing Dystocia
Litter bearing animals First sleeve and physically check First of several fetuses can be stuck in the birth canal
Can compromise the rest of the litter Survivability declines with added time of stress
Canine and feline C-sections Differ from large animal and humans Small animals are put under general anesthesia
Better restraint of animal, fastest and safest way to deliver Cattle and humans – epidural anesthesia
Dystocia Impacts: Calves: severe acidosis compared to a normal, unassisted birth Depressed central nervous system Decreased physical activity and reduced shivering results in more
heat loss and hypothermia. Suckling and the consumption of colostrum may not occur or be
severely reduced 3.2% of unassisted calves (score of 1) were stillborn compared
with 8.4% of calves stillborn with a slight assistance with no jack (score of 2), and 37.2% of calves stillborn with use of jack (score of 3)
Affect on COWS: calving dystocia reduces milk production,
reproductive performance and cow survival and can consequently reduce farm profitability
Swine:A 2013 study showed that: Sows that had a
long duration of farrowing (>300 minutes) have higher repeat breeding rate (pregnant vs. not pregnant at first insemination after weaning
Induction of Parturition Protocols depend upon:
Length of gestationSize and development of fetus
CattleLong acting corticosteroids
Lead to parturition in 2-26 days Wide time range can be disadvantageous May have detrimental effect on dam influencing
preexisting health condition Fetal membrane retention is low
Induction of Parturition
Short acting corticosteroidsFrequently used, very effective Injected within 2 weeks of due dateParturition usually occurs in 24-72 hoursColostral immunoglobulins are normal Influence fetal lung developmentRetained fetal membranes are high
Also related to gestational age of calf: younger calf = high incidence of retained membranes
Induction of Parturition
ProstaglandinsEffective methodNo advantage over corticosteroids
EstrogensOld methodPoor efficacy
Induction of Parturition
CombinationsGoal: reducing rate of retained placentas,
avoiding induction failures and calf mortalityShort acting corticosteroids + estrogenLong acting corticosteroids + short acting
corticosteroids or prostaglandinsShort acting corticosteroids + prostaglandin
Multiple Pregnancies
Greater demand on the mother and increased risk on fetusNutritional demand is higher Iron and folate needs increaseAnemia is reported more frequentlyMorbidity and mortality of twins is higher
compared to singleton pregnancies Increased risk of delivering prematurely
Multiple Pregnancies
Mode of delivery can be more difficultPlays major role in infant outcome, especially
second born twins Cesarian-cesarian Vaginal-vaginal Vaginal-cesarian
Vaginal-cesarian mode is most detrimental to second born twin
Presentation and birth weight of twins greatly affects mode of delivery and outcome of infant
Multiple Pregnancies Congenital defects
Neural tube defects Cardiac abnormalities Bowel atresia
Other problems: Conjoined twins Twin reversed arterial perfusion sequence Poor fetal growth Placentation Amniocity Freemartin (cattle)
Multiple Pregnancies
Animals designed to carry singleton pregnancies: Humans Cows Mares
Animals designed to carry multiple pregnancies: Sows Ewes Queens Bitches Rodents
Management of Calving
Group Calving Pros: Saves labor and saves money Herd animals do not like to be isolated Presence of other cows calving stimulates other cows
Group Calving Cons: Changing social dynamics Biosecurity: transfer of fecal-oral pathogens Herd animals when calving prefer to isolate themselves and can’t Other cows can get maternally aggressive to other calves that are
not theirs Calves can get injured and stepped on by other interested cows
More cows together= less individual attention especially with dystocia If individual attention is needed, harder to safely assist
Individual Calving Pros: Can monitor cows individually for issues and feed intake Minimize biosecurity issues
Only one cows pathogen, only one to two calves exposed No identification issues Safer for cow and workers if assistance is needed Safer environment for calf after birth
Individual Calving Cons: More cost, more labor Isolation is stressful for herd animals- especially heifers
Management of Farrowing Stalls/crates:
Con: sows are completely restrained, thus less exercise for sows
Pros: stall/crate can protect pigs better, reduce labor in cleaning/handling, economize utilization of the space, assist sows/pigs easily, and eliminate or reduce the use of bedding
Pens: Con: requires more cleaning labor, more
space, and sows must be restrained for any physical treatment
Pros: but they allow more sow movement & pens can be converted into nursery or growing pens