Pregnancy Checking — Rectal Palpation Vs. Ultrasound – for Oct. 11, 2010

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Both rectal palpation and ultra-sounding for pregnancy have certain advantages, depending on their intended application. To be accurate, both must have a skilled veterinarian performing the pregnancy exam. I will try and outline the pros and cons of each method for your farming operation. I hope I can also dispel the many myths and fallacies surround pregnancy examination.

Rectal examinations have been performed by veterinarians for eons and very little has changed in this science. It is a relatively quick, cost-effective and safe procedure in the right hands. Accuracy is good in the early stages of pregnancy (30-90 days). In mid gestation (four to seven months) it is not uncommon for veterinarians to be out two weeks to a month in their estimate.

Several things account for this, which are easily explained. Gestational length still varies tremendously. I always use the example of a flush of embryos put into recipient cows. Even though genetics are identical and they are implanted within hours of each other it is not uncommon to have the recipients calving up to one month apart. Depending on breed and sex of calf, gestations also vary greatly. The veterinarian may palpate the nonpregnant horn of the uterus, receiving a false underestimation of pregnancy status. The most important thing is whether the cow is open or is late.

With good setups and in skilled veterinarians hands, rates of up to 100 head per hour can be accomplished.

Abortion risk low

We still hear frequently hear the misnomer surrounding pregnancy examination causing abortions. There is only a very slight risk in the real early stages of pregnancy (around 30 days) and skilled palpators are seldom in the rectum for more than a few seconds, minimizing any risk. We do not manipulate the fetus, as some claim. Rough handling and banging through the chute are more likely to cause abortions then any rectal palpations ever have. One must keep in mind abortions still normally occur in two to three per cent of cattle yearly. This has numerous causes including genetic defects, infectious causes, twinning and trauma.

Equipment simply relies on a good setup, preferably with a palpation cage, o. b. sleeves and lube. Veterinarians always need to find a positive sign of pregnancy. This involves “balloting” the uterus or feeling for the presence of cotyledons. In confirming a cow open the whole reproductive tract is explored. The only cows which are difficult to do are extremely fat ones. Their internal fat pushes the uterus down, making it difficult to reach.

Ultrasound

Ultrasounding requires a large capital outlay for the veterinarian and the diagnostic intent should be a lot different. Reproductive problems can be explored since you can differentiate fluid from pus and make a more definitive diagnosis. If you are interested in fetal sexing (although more difficult and time consuming), this can be accomplished when cows are 55-75 days pregnant. The ultrasound is very accurate in the 30-to 75-day range. It is highly inaccurate staging in the last trimester.

Even though external probes have recently been advertised, they are highly inaccurate in cattle because of the mass of tissue to penetrate. Full bladders are misdiagnosed as pregnancies. Veterinarians would have gladly embraced this concept since rectal palpation is really hard on shoulders and elbows. Unfortunately external probes for pregnancy on large animals are too inaccurate and way too slow. In any pregnancy examination if accuracy of pregnant versus nonpregnant doesn’t reach 99 per cent, it is inadequate.

With a good internal probe (quality of ultrasounds also varies considerably) besides fetal sexing, twins may be picked up. This is something rarely found with straight rectal palpation. Again though, cows must be ultrasounded early in pregnancy for this to be accomplished. Very early embryonic deaths can be diagnosed where you have a fetus but no fetal heartbeat indicating a dead fetus. On open cows, cysts on the ovaries can also be detected and easily differentiated between luteal and follicular. These cysts require a slightly different treatment regime, which your veterinarians can explain.

Preparing the area

In setting up the ultrasound screen, veterinarians usually need the area somewhat shaded and have a safe area to set up in close to the chute. The electronics especially the probe ends, are subject to damage from rough handling and are extremely expensive to fix.

Pictures can be printed if required for a purebred sale. Newer ones have goggles or eyepieces but the veterinarian then becomes a bit limited in helping with other things such as putting on endectocide, vaccinating etc. These machines are now very portable and carried in a backpack or around the waist.

As you can see, both forms of pregnancy examination have merit. Rectal palpation being fast and safe is commonly done in most beef herds where cattle are in the middle or last trimester. Without all the equipment being necessary, it is also considerably less expensive to do than ultrasonography. Ultrasounds generally are used in problem breeders or when specialized procedures such as fetal sexing are required. Cows being sold with sexed embryos are often reconfirmed in calf by rectal palpation later in the year. Rectal palpation for pregnancy is a procedure done by up to 70 per cent of beef producers across Western Canada.

Open cows even purebred ones become a liability to feed over winter. At the same time as pregnancy examination reproductive problems can be explored and cows can be condition scored. All worthwhile procedures in your farming operation. Cows have finally gone up in price so sell the open or late cows and save the winter feed bill.

RoyLewisisalarge-animalveterinarian practisingattheWestlockVeterinaryCentre. Hismaininterestsarebovinereproduction andherdhealth.

About the author

Contributor

Roy Lewis practised large-animal veterinary medicine for more than 30 years and now works part time as a technical services veterinarian for Merck Animal Health.

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