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Parturition

Parturition . Sara Pardall. What is it?. Parturition is the act of giving birth or expelling a fetus from the womb Immediately precedes lactation, and return to cyclicity

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Parturition

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  1. Parturition Sara Pardall

  2. What is it? • Parturition is the act of giving birth or expelling a fetus from the womb • Immediately precedes lactation, and return to cyclicity • Initiated by the fetus and involves a complex cascade of endocrine events that promote myometrial contractions, dilation of the cervix, expulsion of the fetus, and expulsion of the extraembyonic membranes

  3. What happens? • Three stages: • Stage 1- initiation of myometrial contractions • Stage 2- expulsion of the fetus • Stage 3- expulsion of the fetal membranes

  4. Stage 1 • Removal of progesterone block • Fetal corticoids cause placenta to make PGF2@, which gets rid of the progesterone block • Fetal cortisol promotes conversion of progesterone to estradiol using three different enzymes • The production of PGF2@ and estradiol causes the myometrium to become more active and contractions become noticeable • PGF2@ also causes the regression of the CL

  5. Stage 1 • Fetus begins to rotate so the front feet and head are facing the rear of the dam as the pressure inside the uterus continues to increase, if the fetus fails to do this, then it could lead to dystocia • Fetus continues to move towards the cervix applying pressure and dilating the cervix

  6. Stage 1 • Oxytocin levels increase as the pressure against the cervix increases, which causes even more moyometrial contractions. • After this has happened, the fetus goes into the cervical canal • Stage one varies in length

  7. Stage 1 Species Differences • Cow: 2-6h • Ewe: 2-6h • Mare: 1-4h • Sow: 2-12 h • Queen: 4-42h • Human: 8+

  8. Stage 2 • Requires lots of uterine and abdominal muscle contractions • Relaxin: • Stimulated production by PGF2@ • Softens connective tissues in the cervix • Promotes elasticity of the pelvis • Loosens supportive tissues

  9. Stage 2 • Estradiol • Stimulates secretions, especially the cervix • Mucus lubricates the cervix and vagina • Feet and head of fetus put pressure on membranes, they rupture, loss of amniotic and allantoic fluid, also lubricates

  10. Stage 2 • Fetus becomes hypoxic as it enters the birth canal, this in turn promotes even more contractions. • Abdominal muscle contractions also contribute to the expulsion of the fetus • Parturition length is reduced because contractions get stronger as the fetus keeps moving through the birth canal

  11. Stage 3 • In most species, the placenta expulsion follows the expulsion of the fetus quite quickly • Chorionic villi become disconnected from the maternal side of placenta • The release of these villi are initiated by vasoconstriction of arteries in the villi

  12. Dystocia • Any birth that is out of the normal time range for the species • Usually occurs during the second stage of parturition

  13. Dystocia • Management • The sooner the problem is identified the better chance the fetus has for survival • In the event that the fetus is too large to pass through the pelvis several strategies may be used: • Calf jack • Sleeving • Snare • C-section

  14. Dystocia • First time mothers are generally more likely to have dystocia • Can select for birth weight in cattle, highly heritable trait • Abnormal presentation of fetus is a also problem

  15. Dystocia • Multiple births • Twins in monotocous species can be dangerous • First fetus could be backwards and keep the second from coming out • Uterine contractions may decrease after the first is born • The mother may get tired of pushing after the first • Can get Siamese twins

  16. Induction of Parturition • Lutalyse,- contains PGF2@ • Given to swine about three days till due date • Responses may vary • Sows usually farrow within 30 hours of injection • Makes farrowing management easier • Long and short term Cortosteroids are more commonly used in cattle

  17. References • Pathways to Pregnancy and Parturition. P.L. Senger. 2003. pgs 304-306 • Dargats et al.Calving and calving management of beef cows and heifers on cow–calf operations in the United States. Theriogenology. 997-1007.2004 • Suspected Fetopelvic disproportion and abnormal lie

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