Lecture 7- Basic Principles of Bovine Pregnancy Diagnosis

Reasons to pregnancy check cows

ID open cows; treat open cows; reduce feed costs; ID embryonic loss; adjust management; establish cyclicity; cull non‑productive cows

Dairy-specific reason for pregnancy check

ID non‑pregnant cows to rebreed; usually at 30-35 days post AI/exposure

Beef-specific reason for pregnancy check

ID open cows for culling; usually at weaning

Economic value of pregnancy diagnosis

Open beef cow costs $300-400/year; open dairy cow ~$3/day; preg check ~$8-9/head

Producer pregnancy check methods

History of bull exposure; absence of estrus at 18-24 days; unreliable

Transrectal palpation window

35 days gestation to term

Cardinal signs of pregnancy (palpation)

Membrane slip; amniotic vesicle; placentomes; fetus

Uterine retraction purpose

Allows exam of early pregnancies and open tracts up to ~90 days

Direct uterine retraction method

Grasp cervix → stand on external os → hook ventral intercornual ligament → pull tract onto pelvic floor

Indirect uterine retraction method

Grasp cervix → hold back with thumb → grasp broad ligament → follow horn → hook ventral intercornual ligament → retract

Sweeper method

Deep abdominal sweep to bring entire tract into pelvis

Membrane slip definition

Chorioallantois slips between fingers when palpating gravid horn

Membrane slip timing

Detectable 30-90 days

Membrane slip feel

Like strumming guitar string under a towel

Membrane slip caution

Easy to mistake for fluid; risk of slipping uterus through rectal wall

Amniotic vesicle timing

First palpable ~32-35 days; difficult after 55-60 days

Amniotic vesicle significance

Turgid vesicle in pregnant horn; diameter used to age pregnancy

Amniotic vesicle caution

Excessive pressure may damage embryo

Placentome definition

Maternal caruncle + fetal cotyledon

Placentome palpation timing

First palpable ~80 days

Placentome number

~120 arranged in 4 rows

Placentome size variation

Dime to silver dollar; most consistent just cranial to cervix

Placentome exam rule

Palpate ≥3 placentomes before aging pregnancy

Fetus first palpable

55-65 days

Fetal descent timing

Begins ~70 days; complete ~150 days

Fetal ascent timing

Begins ~210 days; complete ~240 days

Fetal size benchmarks

60d mouse; 90d rat; 120d small cat; 150d Beagle; 210d Doberman

Supportive signs of pregnancy

Horn asymmetry; uterine wall thinning; cervix fixation; fremitus; CL presence; uterine fluid

Fremitus definition

Vibration in middle uterine artery within broad ligament

Fremitus timing

3 mm at 3 mo; 6 mm at 4 mo; 9 mm at 5 mo; 12 mm at 6 mo (ipsilateral); 12+ mm at 7 mo (bilateral)

Fremitus caution

Do not confuse with immovable iliac artery

Best accuracy window for palpation

35-40 days for experienced palpators; 50-55 days for less experienced

Early pregnancy diagnosis factors

Uterine size/thickness; heifer vs cow; breed differences; parity; palpator skill

Breed difficulty note

Jerseys are the hardest due to tract length and ligament anatomy

Hazards of palpation

Rectal perforation; rupture of amniotic vesicle; fetal heart sac rupture; PGF2α release causing pregnancy loss

Ultrasound usefulness window

Most useful after 24 days

Ultrasound fetal heartbeat

Detectable after ~24 days

Ultrasound fetal sexing

55-80 days

Ultrasound advantage

Can detect early embryonic death (EED)

CRL aging example

12-12.5 cm = 80d; 14.5-16 cm = 90d; 19 cm = 95d; 20-21 cm = 100d; 23-24 cm = 110d

Other fetal measurements

BPD, HL, TD used for gestational aging

Placental type in cattle

Synepitheliochorial, cotyledonary

Pregnancy-specific protein B

Secreted by trophoblast; detectable ≥30 days post breeding; BioPRYN test

BioPRYN limitations

PSPB remains high after calving; cannot detect very early pregnancy loss

Progesterone test timing

20-24 days post breeding

Progesterone test limitation

Many false positives (pyometra, ovarian abnormalities, poor heat detection)

Progesterone test utility

Best used to detect OPEN cows (absence of P4)

Estrone sulfate

Placental product; useful after 100 days; limited practicality

Pregnancy detection methods list

Transrectal palpation; transrectal ultrasound; PSPB; milk/blood progesterone

Palpation false positives

Fluid in uterus; pyometra; slipping non‑gravid horn

Palpation false negatives

Early pregnancy; poor technique; fat cows; Jerseys

EED role in diagnosis

Early embryonic death may cause false negatives if checked too early

Safety of palpation

Generally safe when performed correctly

Fetal membrane slip exam trap

Can be mistaken for slipping uterus through rectal wall

Amniotic vesicle exam trap

Excess pressure may cause intestinal atresia (association)

Placentome exam trap

Must differentiate from uterine thickening or pathology

Fremitus exam trap

Iliac artery vibration misinterpretation

Best pregnancy aging method early

Vesicle diameter + horn diameter

Best pregnancy aging method mid

Placentome size + fetal size

Best pregnancy aging method late

Middle uterine artery diameter + fetal size

Ultrasound operator variability

Breed, genetics, equipment, and operator skill affect measurements

Blood tests vs palpation

Blood tests useful for large herds; palpation gives immediate results

Open cow management

Rebreed dairy cows; cull beef cows

Palpation requirement

Must ID at least one cardinal sign of pregnancy

Uterine retraction exam trap

Pregnant tracts >90 days cannot be retracted; retract upward, not backward

Fetal descent clinical relevance

Fetus out of reach mid‑gestation; must rely on placentomes and fremitus

Fetal ascent clinical relevance

Late pregnancy fetus returns to pelvic inlet; easier to palpate

Ultrasound fetal development landmarks

Heartbeat ~21d; limb buds ~30-33d; placentomes ~35d; ribs ~52-55d

Ultrasound fetal sexing landmark

Genital tubercle location (male cranial; female caudal)

Pregnancy detection client considerations

Dairy: rebreed; Beef: cull; cost efficiency

Pregnancy detection exam trap

Must differentiate pyometra from pregnancy (fluid + CL + no estrus)

BioPRYN cost

~$2.50/test + shipping + blood collection

Progesterone test exam trap

High P4 ≠ pregnancy; low P4 = open

Ultrasound advantage over palpation

Detect EED; visualize fetus; measure structures

Palpation advantage over ultrasound

Faster; cheaper; no equipment; immediate herd-level use

Rectal exam landmark

Cervix is primary landmark for tract orientation

Fetal aging by size

Mouse/rat/cat/Beagle/Doberman scale

Fetal descent/ascent exam trap

Mid-gestation fetus out of reach → rely on placentomes

Pregnancy diagnosis goal

Accurate identification of open cows to improve herd efficiency