Pregnancy Detection & Gestation
Animal
Breeding
Pensacola
Jr College
Methods of Pregnancy Detection
w Rectal
palpation
w Progesterone
assay in milk
w Progesterone
assay in blood
w Pregnant
mare serum gonadotropin (PMSG) assay in blood
w Ultrasonography
Rectal Palpation
w Can
only use in domestics, with proper restraint
w Large
domestics (cow, horse):
•
Insert arm into rectum,
direct palpation of reproductive tract
•
Must know expected differences
at various stages
•
Must know species differences
Rectal Palpation (cont’d)
w Small
domestics (ewe, doe):
•
Rod insertion into rectum to
press down tract (not recommended due to tearing / bruising)
•
Then hand palpate under
abdomen
Rectal Palpation (cont’d)
w Potential
for misdiagnosis:
•
Lack of knowledge
•
Pyometria
(pus in uterus due to fetal death)
•
Metritis
(non-specific uterine infection)
•
Mummified fetus
Rectal Palpation
Rectal Palpation (E.T.)
Progesterone assay - milk
w Used
in dairy cows, potentially in lactating mares
w High
progesterone levels in milk continuing 21 days post-breeding = pregnancy
w Qualitative
kits used on farms compare large groups of cows, cheap method
Progesterone Levels in milk (cow)
Milk assay results
NON-PREGNANT
Progesterone assay - blood
w Radioimmunoassay
detects continuing high progesterone levels = pregnancy
w Test
accuracy:
•
Ewe = 18 days post-breeding
•
Doe = 21-23 days
post-breeding
•
Cow = 21-24 days
post-breeding
Camel Progesterone Radioimmunoassay
PMSG assay - blood
w Radioimmunoassay
can be used in horses to detect pregancy
w First
appearance of PMSG in mare’s blood around 40 days post-breeding
w Accurate
mare assay from 50 – 100 days post-breeding
Ultrasonography
w Expense
is biggest difficulty
w Accurate
pregnancy detection at:
•
20 days in cow
•
100 days in ewe / doe
(decrease to 45 days using intrarectal ultrasound)
•
10 days in mare (but wait to
18)
•
35 days in sow
Simple Ultrasound
Use in Sow
Use in Ewe
Complex Ultrasound – Llama at 120 days
Gestation = period of pregnancy (fertilization to birth)
Twinning
w Fraternal
/ dizygous twins = two eggs ovulated and fertilized
by different sperm
w Identical
/ monozygous twins = one egg ovulated and fertilized
by one sperm, splits into two embryos
Stages of Gestation
w Migration
and spacing of embryos in uterus
w Cleavage
divisions
w Morula
w Blastula
w Formation
of inner cell mass and trophoblast
Stages of Gestation (cont’d)
w Zona
hatching
w Gastrulation
w Cells
of inner cell mass à
germ layers
w Development
of extraembryonic membranes
w neurulation
Embryo spacing (sow)
Cleavage divisions = division without growth
Morula
= 8-16 cell embryo
Blastula = hollow ball of cells, fluid-filled
Inner cell mass / trophoblast
Zona
Hatching
Gastrulation
= inpocketing of surface
Germ Layer Formation
w Ectoderm
à
skin, nervous system
w Mesoderm
à
circulatory, skeletal, muscle, repro, excretory systems
w Endoderm
à
digestive system, liver, lungs, pancreas, glands
Germ Layers / Gastrulation
Extraembryonic
Membranes
w Develop
from ectoderm, mesoderm, and trophoblast for
implantation
w
Amnion
w
Chorion
w
Allantois
Extraembryonic Membranes
Neurulation
= ectoderm folds at neural crest to form brain & nerve cord
Example: Zoo
Pregnancy Detection Research
w “Pregnancy
Diagnosis in Wild Canids Using a Commercially Available Relaxin Assay”
w St.
Louis Zoo