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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