The evolution of pregnancy confirmation in cattle

  In earlier days of cattle domestication, with generally smaller herds closely observed, the “art” of pregnancy detection involved close inspection of the vulva.    “Open” cycling cows showed a visible “heat” cycle by more moving about, bawling, and mounting activity.    Their vulvas were slightly swollen, protruding outward, lubricated, and pinkish colored from elevated blood flow.    Once pregnant, the vulva would recede, its outer skin folded flat and wrinkled, and the interior was “bland” without color or lubrication.
Only trouble was, a non-cycling cow (C.L. cystic) would be like a pregnant cow, but empty of a calf.    As veterinary practices developed, detection and treatment of “cystic” ovaries required palpation.   Alongside palpation came determining or confirming pregnancy.   From a veterinary view, when you ask for cows to be “pregnancy checked” your vet is likely thinking, checking for “open” cows (and diagnosing why they might be open after being exposed to breeding) is the important part of the process.
As the medical industry developed electronic technology used by obstetricians, this equipment found its way to veterinary practices, and “Ultrasound” became the popular option.    Carrying the signal probe into the rectum in their glove, they can palpate both uterine horns as well as ovaries, studying the various structures, and when pregnant, a picture of the nascent calf would show up on the computer screen.     This can be done safely a couple weeks earlier than we did for manual pregnancy palpation, which again, is mostly important for detecting “open” cows.

The problem with both manual palpation and ultrasound viewing of possible pregnancy, there is a risk of dislodging the conceptus prior to “fetal transformation” (        approximately six weeks, or 42 days, when the fetal attachment has transitioned from a single membrane to the caruncles and cotyledons all about the uterine horn ).    It is definitely good to know at 30 days post-breed when a cow is “open”;  it is relatively immaterial to know she is pregnant at a time when she is still at risk for early-term abortion.    Thus the value of blood or urine tests to tell us cow is still pregnant at 60 days, a time after which abortion rarely occurs without serious illness.