Parturition: By-dr. Dhiren Bhoi

Learning Objectives To understand what happens to cause parturition and what happens during and after parturition. To understand the hormonal control of parturition. To understand retained placentas, artificial induction of parturition and uterine involution.

How Was Mechanism For Parturition Discovered? Skunk Cabbage Sheep consuming this type of vegetation in western US had prolonged gestations. Fetus had congenital hypoplasia of Anterior Pituitary Gene Defect Autosomal recessive gene in Holstein breed Large calves grow in utero 1-2 months beyond delivery date. Congenital hypoplasia of Anterior Pituitary

Corn Lily (Vertatrum californicum)

Fetus Sheep Cyclops

Lamb

Pictures courtesy of USDA Poisonous Plant Research Lab in Logan, UT. Richard Davies and Robert Poppenga; University of Penn School of Veterinary Medicine Computer-Aided Learning Project

Initiation and Control of the Parturient Process

Hormonal Changes that Control Parturition Hypothalamus

Steps Fetal ACTH causes -

Fetal anterior pituitary gland

Corticotropic Releasing Hormone CRF Time of parturition is controlled by maturation of the hypothalamuspituitary-adrenal axis

Adrenalcorticotropic Fetal Corticosteroids Hormone (ACTH) causes Removal Blocks Parturition Progesterone levels Infusion Stimulates placental production induces oxytocin receptor or CL regression) parturition Fetal in myometrium Adrenal Production of Estrogens Estrogen by placenta (Increase) Corticosteroid PGF2α production by uterus -

Pine-needle abortion in cattle - cause by a corticosteroid-like product

Glucocorticoid

Redrawn from Liggins, G.C. 1969. In Foetal Autonomy

Progesterone (Decrease) Prostaglandin F2α (Increase)

Mare The day of parturition may occur through corticosteroids but the time (minute) of the day is regulated by the release of oxytocin from the mare.

Hormonal changes cause: 1. Final maturation of fetus

Cortisol - stimulates lung surfactant

2. Expansion of birth canal

Initiates parturition and lung development

3. Maternal behavior 4. Synthesis and ejection of milk 5. Initiation of uterine contractions 6. Termination of pregnancy Fescue toxicity problems: Ergot causes inhibition of prolactin release and thus milk production

Prolactin completes final mammary development and milk secretion

Significance of initial hormonal changes Progesterone - removes block on uterine contractions. Allows myometrial muscle fibers to work together in bundles Estrogen - makes uterus more responsive to induction of contractions i.e., more irritable and smooth muscle tissue stimulation. Induction of oxytocin receptors Events just Prior to Parturition: 1. Pelvic ligaments soften - Tail head sinks due to estrogens and relaxin. 2. Cervix softens and begins secreting stringy mucus - estrogens and relaxin. Increased water content in cervical tissue and cervical plug is removed

3. Swelling of vulva. Collagenase breaks down collagen which also widens the pelvis 4. Udder swells - fills with first milk and due to edema: Prolactin, Estrogens and glucocorticoids 5. Fetus moves into proper position - resting on thorax, front feet and head facing the cervix

Stages of Parturition: I. Dilation of Cervix. (2-6 hours, cow) Heifers 12 hours Uterine contractions become coordinated and regular Synchronized Estrogen & PGF2α induced This occurs because progesterone has declined Fetus pushed against cervix - amnion dilates cervix Stimulates oxytocin release Chorioallantoic membrane may break 1st Water Bag Pressure of fetus in cervix stimulates oxytocin release and reflex Ferguson contractions of abdominal muscles. Reflex Contractions force the calf legs and head to spread cervix

II. Expulsion of Fetus (.5-2 hours, cow) Longer than 2 hours considered to have dystocia Strong uterine contractions due to synergistic actions of high estrogen, PGF2α and oxytocin Strong abdominal muscle contractions Amnion ruptures - mucin lubricates vagina - vestibule 2nd Water Bag Fetus passes through vagina - vestibule. Cause of death in 6.4% of calf losses on average

Three Barriers in Delivery of a Calf

1. Head

2. Shoulders

3. Hips

Sow Delivery of Piglets

Length of Stage II in sow is 2 to 4 hours Delivery of piglets is usually between 8 to 45 minutes between each one. Delivery will alternate piglets between horns Last 1/4 of horn in large litters increases the chance of stillborn Length of umbilical cord Uterine horn contracts to shorten distance after delivery of each piglet

III. Expulsion of the Placenta (4-5 hours, cow) Uterine contractions continue Blood forced from cotyledon villi - shrinkage separates cotyledon and caruncle Prolapsed uterus cow tired need to give Contractions push placenta out oxytocin Causes of retained Placentas: -Infections caused adhesions between cotyledon and caruncle -Calving stress - twins or calving difficulty - edema of cotyledon - won't separate from caruncle -Weak uterine contractions - villi won't shrink Oxytocin Milk fever - Calcium low

Care of retained placentas: Do not manually remove from uterus; uterine damage greater than infection of retained placenta Do not pull placenta out even in Mare! Check to see placenta is fully intact in Mare or you need a Veterinarian to clean her out. Don’t breed on foal heat if there is a problem Infuse Bovine uterus with tetracycline and systemic injections of penicillin until placenta passes ~ 2-4 days. Don’t give mare tetracycline as this will cause inflammation!! Can treat cow with either PGF2α or oxytocin (ergonovine) to expel the infection

Preventing retained placentas: Vaccinate for Brucellosis and leptospirosis Make sure Vitamin A, E and Selenium are not deficient in diet Don't have cows over-conditioned at calving Have sanitary calving conditions Allow heifers to be large enough at calving and don't breed to bull that sires larger calves than your female can handle. Size of pelvis Feed and develop heifers before breeding

Uterine Involution: Cow passes lochia - 1 to 2 weeks after birth. (mucus, blood, fetal membranes and surface of caruncle). Caruncle regenerated by ~ 30 days post calving Uterus completely involuted by 45 days postpartum 80 -90% done by Day 6 Shrinking of uterus due to muscle contractions Involution enhanced by: suckling periods estrogen.

oxytocin release by estrus

Foal heat 10-15 days postpartum in mare can have good fertility if there are no problem with of involution. Sows can express a heat 7 days post-partum - However there is no ovulation with it

Artificial Induction of Parturition: Reasons: Time parturition to labor costs Need to know status and size of fetus Avoid dystocia (Large Fetus) How to do it: Must have Management First! Must Know Breeding Dates!!! Give ACTH Give Corticosteroids. (Dexamethasone) Give PGF2α Give Oxytocin

Cow - Do not induce before last 7-14 Days of gestation Method: Dexamethasone - parturition in 48 hours, 20-50 mg/IM Azium (trade name) combined with 25 mg Lutalyse induces within 35+2 hours. Requires a live fetus work, does not work on a mummified fetus -High incidence of retained placentas and lower postpartum fertility. If cow are induced early Retained placenta is not problem if treated properly - Giving estrogen before induction of parturition incidence Prostaglandins used in cases of a mummified fetus and are also effective in inducing abortion the first 4-5 months Example for inducing parturition in beef cattle: Sixty breeding season, induce cows 265 days from last day of breeding season

Sheep - Best within a few days of parturition 5 to 7 days Dexamethasone (8-20 mg) Parturition in 24-72 hours Retained placenta not a problem Can use Lutalyse to abort before Day 50 of gestation

Goat - CL is important throughout pregnancy Can use Lutalyse to induce 5-7 Days prior to normal time of parturition

Sow - Do after day 111 of gestation Note that this is less than 3 Days from normal parturition PGF2α (Lutalyse 10 mg/IM) parturition in 29-48 hours. Close synchrony - Lutalyse at 8 AM followed by oxytocin 40 IU 24 hours later. Sows farrow between 8 AM and 5 PM (32 hours from start) Piglets should be born within 1 to 8 (average 1-4) hours with 15 minute intervals between piglets - May give oxytocin in last few piglets to decrease stillborn numbers in large litters or after extended delivery interval Its is important to give PGF2α no sooner than Day 111. If given on Day 110 will cause stillborn piglets ( too immature to survive)

Mare - Do after day 320 of gestation Oxytocin (20-60 I.U.) close to term !!! Takes less than 1 hour! Placenta expelled in < 1 hour Make sure of the following before inducing foaling: 1. Udder is enlarged with presence of colostrum 2. There is relaxation of the perineal region 3. Cervical relaxation (can insert 1 to 2 fingers) Usually induce for only two reasons: 1. Demonstration 2. Prolonged gestation In normal pregnancy, mare can control time of day for foaling through her release of oxytocin. Inject oxytocin give no choice of time.

Bitch - If needed to get rid of unplanned mating Give Prostaglandin F2α at: .25 µg/kg body weight 3X/day for 3 to 4 days

Induction of Abortion in Feedlot Heifers 1. All females in a feedlot should be examined rectally for pregnancy, and abortion induced at that time. 2. Animal induced to abort should be in good health and well adjusted to the feedlot. One should always remember, abortion will be stressful and combined with any other stress (diseases like shipping fever, pneumonia, etc.) can cause extreme losses in gain efficiency or even death. 3. Growth promotants containing progesterone or analogues to progesterone may interfere with induction of abortion and should be withheld until after abortion occurs.

Procedure: 1. Heifers that are less than 150 days into gestation can be aborted with a single intramuscular injection of 25 mg Lutalyse or 500 µg Estrumate Efficiency of 90%. 2. After 150 days of gestation, combination of 25 mg Dexamethazone and 500 µg Estrumate is needed to cause abortion. Efficiency of 95%. 3. Abortion will occur over 2 to 10 days. 4. All abortions should be recorded, and heifers which fail to abort re-examined. 5. Failure to induce abortion is most likely caused by failure of luteolysis. Retreatment will usually cause abortion. 6. In the case of fetal mummification, Prostaglandin treatment will stimulate expulsion. 7. Cows over 4 months pregnant will have a high percent of retained placenta (80%). Most cases will resolve themselves, but the producer needs to monitor health of females after abortion.