Normal parturition in bovine Flashcards
Parturition means…
(partus, tocos) e. delivery: Expulsion of fully grown fetus and fetal membranes from the uterus through the birth canal.
Normal parturition (eutocia)
Right time (in cow, the length of pregnancy is 270 – 290 days).
One week before or after the term we consider as normal in cow.
the length of pregnancy in days in the cow
270 – 290 days
The Birth canal is divided into: (2)
Bony canal and soft tissues
Bony = (pelvis, 2 coxal bones, sacral bone)
Obstetrical pelvimetry
is the assessment and measurement of the dimensions of the pelvis, particularly focusing on its suitability for vaginal delivery.
Not used much in practice (in vet med).
Pelvic cavity narrows in caudal direction.
Cranial and caudal terminal line anatomic points.
Fetal postures can change until
the beginning of first stage of parturition (opening of birth canal).
Before parturition fetus front legs will be extended towards to birth canal, but the elbow joints will be flexed.
Final extension of front legs will happen during the second stage of parturition (fetus expulsion stage).
In normal parturition the fetus will be born in anterior presentation, dorsal position and extended postures (front legs and head are extended toward the birth canal).
Hormonal activity to induce parturition.
Activation of fetal hypothalamus-hypophysis-adrenal glands axis and fetal cortisol release.
Placental origin estrogens, progesterone, PGF2α and corticotropin release factor (CRF) will influence hypothalamus.
Two major endocrine-change events in the dam aiding parturition:
- Removal of the myometrial „progesterone block“ enabling myometrial contractions to begin.
Fetal cortisol promotes the synthesis of three enzymes that convert progesterone to estradiol.
- Increased reproductive tract secretions (particularly by the cervix).
Fetal cortisol triggers androstenedione which is converted finally to estrogen (initiates secretory activity of the reproductive tract in general and particularly the cervix).
Progesterone block removal“
Fetal cortisol promotes the synthesis of three enzymes that convert progesterone to estradiol.
Relaxin is a Glycoprotein that is produced by
either the CL or the placenta, depending upon the species.
Synthesis is stimulated by PGF2α.
In the cow, from 150 – 200 days of pregnancy the main source of progesterone is
the placenta, however the presence of CL in an ovary is necessary until parturition.
If we will remove the CL after day 200 of pregnancy, the pregnancy will continue, but the normal hormonal mechanism which will cause the start of parturition process will be disturbed.
Body temperature in cows before parturition.
Body temperature rise during last months of pregnancy 38.8° – 39.3°, when parturition approaches 39.4° – 39.7°.
Sharp drop 12h before parturition (as low as 38°).
According to what 3 factors can we predict the parturition time in all cows with accuracy 22h?
pelvis ligament relaxation,
body temperature drop
and progesterone level decrease
define Ferguson reflex
a neurohormonal reflex that triggers strong uterine contractions during labor. It is initiated when the fetal head presses against the cervix, stimulating stretch receptors.
This pressure sends nerve signals to the hypothalamus, leading to the release of oxytocin from the posterior pituitary gland.
Oxytocin then increases the strength and frequency of uterine contractions, further enhancing cervical stretch and facilitating labor progression. This positive feedback loop continues until delivery occurs.
On average up to ? abdominal muscle contractions are needed for expulsion of fetus.
On average up to 60 abdominal muscles contractions are needed for expulsion of fetus.
An Opening cervix feels…?
shorter in rectal palpation
Stages of birth:
- opening of the birth canal.
- fetal expulsion stage.
- expulsion of fetal membranes.
Describe opening of the birth canal.
very difficult to determine the beginning of it (beginning of labor). Duration approx. 2-6 h.
Cow is restless, apparent discomfort, cessation of eating, pawing the ground, circling. Lying down and then fairly quickly rising again.
bluish, vascular semitransparent membrane appearing at the vulva is the chorioallantois. It may be termed the „the first water bag“.
Its rupture together with appearance of fetal front legs and head in vagina is considered also as end of the first stage of birth.
Describe the Second stage of birth (fetus expulsion stage):
length of the stage is 0.5–4h (average 70 min)
The calf is normally preceded by its amnion as it enters the birth canal and unless prior rupture occurs, the amnion appears as a gray-white avascular sac at the vulva (different to the earlier blue one, the chorioallantois.
The calf should be born within 2 hours of the first appearance of the amnion at the vulva.
During second stage of birth one uterine contraction lasts 1 – 2 min (during that time several abdominal contractions).
During delivery, the position of the calf may rotate approximately 45⁰ to the right or left allowing it to take advantage of the greatest pelvic diameter of the mother.
In case of twins, after the expulsion of first fetus the labors will cease for
10 – 15 min and then the second fetus will be delivered.
The calf should be born within ? hours of the first appearance of the amnion at the vulva.
The calf should be born within 2 hours of the first appearance of the amnion at the vulva.
Although the bovine fetus can survive for up to 8 hours during the second-stage of labor, this is not always the case and any delay should be investigated.’
What stimulates the calf to breath at birth?
Obstruction of umbilical cord,
increase in carbon dioxide,
stimulation of respiratory center.
