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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