Reproduction in Domestic Animals - Facultad de Ciencias Veterinarias

16 t h International Congress on Animal Reproduction
26 Workshop Abstracts
Workshop 18 - Pregnancy, fetal well-being and the periparturient
dam
Moderator: Marcel A. M. Taverne (The Netherlands)
WS18-1
Assessment of fetal well-being during bovine and equine
gestations resulting from in vivo and in vitro produced
embryos
Chavatte-Palmer, P
INRA, UMR 1198; ENVA; CNRS, FRE 2857, Biologie du Développement et
Reproduction, Jouy en Josas, F-78350, France
Pregnant dams need to be monitored in order to precociously diagnose
any pathological process and start treatment. Pregnancies established
after natural breeding or artificial insemination may not require
specific monitoring if the dam is reproductively sound and in absence
of maternal pathology (i.e. colics in horses). In contrast, in vitro
produced embryos, and particularly cloned embryos, have been
associated with severe placental abnormalities and fetal losses,
requiring regular assessment of the health of both the recipient and the
fetus.
In terms of imaging technologies, rectal and transabdominal
ultrasound scanning have been used for a long time in the horse to
assess fetal growth and activity and evaluate placental health (mainly
through the measurement of the utero-placental thickness) throughout
pregnancy. Transabdominal ultrasound has also been used
successfully in cattle to diagnose the Large Offspring Syndrome
(increased fetal size, placental edema, abnormal placentome
structures) before clinical signs are prominent and maternal welfare is
affected. Transrectal doppler sonography of the uterine artery can also
be performed to evaluate uterine blood flow both in the mare and the
cow and will provide helpful information on placental perfusion.
More recently developed methods, like 3D Doppler scanning, are
being evaluated for visualizing the placenta in ruminants, but the use
of Magnetic Resonance Imaging is precluded both because of the
price and the size of the animals. Ultrasound guided amniocentesis
and allantoidocentesis have been performed both in cattle and horses
but remain so far too risky for routine use, especially if repeated. It
would be worth, however, developing safe procedures to be used in
practice as this is a simple technique providing potentially very useful
clinical information. Finally, placental biopsies can be performed in
cattle but may not provide significant information on fetal well-being.
Most useful maternal blood markers for fetal well-being include
estrone sulfate and progestagens in the horse. In cattle, the maternal
plasma concentration of placental Pregnancy Associated
Glycoproteins (PAG) is routinely used for pregnancy diagnosis but
may also be helpful in detecting animals likely to develop the Large
Offspring Syndrome. Finally, the diagnostic and prognostic interest of
other molecules, such has the acute phase protein Serum Amyloid A
(SAA) must yet be explored.
WS18-2
Monitoring of the bovine fetus during and shortly after
birth
Bleul, U
Department of Food Animals, Clinic of Reproductive Medicine, Switzerland
Approximately 3% of all bovine fetuses die during or shortly after
birth. In the majority of cases the reason for this peripartal mortality is
dystocia. This bears the risk of fetal damage caused by hypoxia,
hypercapnia and acidosis. In the field methods for monitoring the
well-being of the fetus during parturition are almost lacking. The
evaluation of vitality is based mainly on reflexes, meconium staining
of the fetus and the amniotic fluid or the detection of a heart beat in
the fetus, but they do not allow an accurate estimate of fetal acidosis.
In the last years new methods were described which may help to
recognize fetal distress.
In human medicine, cardiotocography measurement is the standard
procedure for fetal monitoring intrapartum and has been evaluated in
experimental studies with bovine fetuses. Cardiotocography measures
the fetal heart beat and the intrauterine pressure continuously and the
fetal heart rate correlates well with the neonatal outcome.
Further methods were recently described, which measure the fetal
oxygen saturation or blood gas parameters. Oxygen saturation was
measured using pulsoximetry by placing an oxygen sensor in the
mouth against the mucosa of the hard palate of the fetus. Although
postnatal acidosis can be predicted by continuously measuring the
oxygen saturation of the fetus intrapartum, technical modifications are
required to improve its usefulness. In experimental studies, bovine
fetal blood has been collected transvaginally from the umbilical
vessels, by centesis or catheterization of the carpal or digital veins.
Capillary blood has been collected from the dorsolateral aspect of the
distal pastern when the calf’s forelimbs protrude from the vulva.
Blood gas values during stage II labor were suitable in order to
diagnose fetal asphyxia and selected parameters showed high
correlations with the level of postnatal acidosis.
Determination of blood gas values of venous blood is an established
method for detecting the metabolic component of the mixed
metabolic-respiratory acidosis in calves immediately after birth.
Because the respiratory component of acidosis is difficult to
determine with venous blood, collecting arterial blood is a more
reliable method for evaluating pulmonary function by determination
of the partial pressure of carbon dioxide and oxygen of arterial blood.
Various methods of monitoring the calf during and after birth have
been established which may reduce fetal mortality by indicating the
right time for an obstetrical intervention, or the necessity of a
therapeutic intervention in the newborn calf.
WS18-3
The sow and her piglets during the farrowing process
Van Dijk, J
Faculty of Veterinary Medicine, Utrecht University, The Netherlands
Perinatal asphyxia is an important cause of perinatal mortality and
reduced viability and vitality of newborn piglets. The occurrence of
perinatal asphyxia is clearly associated with the farrowing process.
Consequently, several factors affecting the duration of the expulsive
stage of farrowing (DF) have been identified. Whereas the effect of
parity is controversial, breed significantly affects DF and in this
respect the Meishan holds a rather unique position as the number of
stillbirths is not related to DF. Furthermore, a decreased gestational
length and increased number of liveborn and / or stillborn piglets
result, independently of each other, in a significant increased DF. To
lower the risk for perinatal asphyxia at birth, attempts have been made
to reduce the DF by administration of oxytocin. However, despite a
reduction of DF, increasing numbers of intrapartum stillbirths with
ruptured umbilical cords and severe meconium staining at birth are
observed. Regarding factors affecting individual birth intervals
between piglets (BI), it has been shown that higher birth weights,
posteriorly presented piglets and stillborn piglets are associated with
increased BI. Besides, a curvilinear relationship exists between rank
(relative position in the birth order) and individual birth intervals and
breed significantly affects this relationship. Several of the factors
affecting BI are also shown to affect acid-base balance values in
umbilical artery blood samples of liveborn piglets at birth. Piglets
born with ruptured umbilical cords show significantly lower pH
values and a tendency for higher pCO2 values at birth. Interestingly,
decreased birth weights are associated with a slightly more severe
metabolic acidosis at birth. Furthermore, posterior presentation at
birth, increasing cumulative birth intervals and an increasing rank
result in a more pronounced mixed respiratory-metabolic acidosis at
birth. The degree of acidosis that gradually develops during the
expulsive stage of farrowing is not as severe as observed in newborn,
highly asphyxiated piglets at birth. Consequently, it has been stated
that traction, occlusion or rupture of the umbilical cord is an
inevitable factor in the evolvement of birth asphyxia and concomitant
mortality and reduced viability at birth. However, a model of
umbilical cord clamping (average duration of cord clamping: 7
minutes) in late pregnant sows suggests an additional role of
cumulative uterine contractions, occurring during the expulsive stage
of farrowing, in the evolvement of a more or less severe degree of
birth asphyxia.