Modern technology provides a variety of ways to perform a pregnancy diagnosis.
However, the age-old method of rectal exam is still much in use and offers many advantages.
Veterinarians often have their specific preference, but in specific situations one method may offer a distinct advantage over the other.
The two most common methods are manual rectal palpation, which has stood the test of time, and ultrasound, which has become easier to do as technology improves and equipment becomes smaller.
Methods that use blood or milk samples have a place in limited situations but cost more and have delayed results.
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Rectal palpation in most situations in beef herds under a skilled veterinarian is fast, efficient, safe and relatively accurate throughout most of the pregnancy. It is quite accurate in the early (30 to 100 days) and late (seven to nine months) stages of pregnancy.
Palpation can still detect a pregnancy in the middle trimester but the accuracy as to stage of pregnancy can easily be plus or minus one month.
Experienced palpators are fast and gentle and do no damage by touching the fetus, especially in late pregnancy.
One must be especially gentle in the 30 to 60 day time frame, especially if the uterus must be retracted to make the diagnosis.
Research has found that rough palpation at precisely 35 days of pregnancy leads to a higher incidence of atresia ani (born without a rectum). The fetus is quite resilient further along in pregnancy.
Rectal palpation will still be the method of choice for most beef operations.
It frees the vet from carrying the ultrasound machine and allows him to help push cattle up the alleyway, vaccinate or apply endectocide, which helps speed the operation.
A palpation cage is needed to protect the veterinarian and allow quick pregnancy checking.
Most veterinarians prefer that cows be caught and held because posts placed behind them make for a dangerous situation if the cow drops down with the vet’s arm still in the rectum.
Ultrasounding is now primarily used in dairies, where most pregnancy diagnosis is done early in the first 28 to 60 days of pregnancy. It has a few advantages over rectal palpation at this early stage.
It is accurate at this stage, and exper ienced veterinarians can often detect twins and may do fetal sexing at 55 to 70 days of pregnancy.
The right ultrasound view is needed with fetal sexing, which naturally slows down the process. Early embryonic death may be detected, which happens when a fetus is found without a fetal heartbeat.
Experienced practitioners can diagnose pregnancies in the 27 day range in cattle and earlier than that in horses.
A probe will still be used rectally, much like rectal palpation, but less manipulation of the uterus is needed with the early pregnancies.
Less manipulation also means less wear and tear on the arms and wrists of the palpator.
Newer machines have goggles that the operator wears to see the image more clearly. Practitioners previously had to bring out a monitor, which required proper lighting and a shroud if done outside.
The new technology can still break down and batteries can go dead, which means a back-up plan is required.
Pictures can be taken for insurance purposes with some machines and may have a place in sales or for high-end animals.
Palpation cages may not be available In feedlots. If so, inserters can be pushed into the rectum with the probe attached.
These are used for pregnancy diagnosing small ruminants such as alpacas, where manual rectal palpation is out of the question because the rectum is too small.
Ultrasound has less value at auction markets because they are inaccurate at staging the middle and far along pregnancies. As well, ultrasound equipment is expensive and does not stand up to the rigours of being bumped or dropped.
Generally, pregnancy testing with ultrasound is slower and costs more because of the equipment.
Tests have been developed for blood and milk progesterone, which under certain situations have a place. The main drawbacks are cost and the delay factor in finding out the results.
They may be useful if a veterinarian is not available or a long distance away. They are also slightly safer because the fetus is not touched and have good accuracy unless cattle are tested at less than 30 days.
However, they can also miss the early embryonic deaths.
