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