December 2005

 Pregnancy Checking — Rectal Palpation Versus Ultrasound   

By Roy Lewis DVM

Both rectal palpation and ultrasounding for pregnancy have certain advantages depending on their intended application. Both, in order to be accurate, must have a skilled veterinarian performing the pregnancy exam. I will try and outline the pros and cons of each method so you can see how to best fit them into your farming operation. Many myths and fallacies surround pregnancy examination and hopefully these will also be dispelled in this article.

Rectal examinations have been performed reliably 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 (4-7mths) 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 with up to a one month spread. Depending on breed and sex of calf gestations also vary greatly. The veterinarian may also palpate the non-pregnant horn of the uterus giving a false underestimation of pregnancy status. The most important thing is whether the cow is open or is late.

With a good setup and skilled veterinarian’s hands, rates of up to 100 head per hour can be accomplished. A misnomer of pregnancy examination causing abortions is one we still hear frequently. 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 – drastically minimizing any risk. We do not manipulate the fetus as is talked about. Rough handling and banging through the chute are more likely to cause abortions then any rectal palpations ever have. A fetus is very well protected in the cow’s abdomen. One must keep in mind that abortions normally occur in 2-3 % of cattle yearly. These have numerous causes including genetic defects, infectious causes, twinning and trauma. 

Equipment to palpate simply relies on a good setup, preferably with a palpation cage, ob. 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. These cows take a bit of extra time.

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 interested in fetal sexing this (although more difficult and time consuming) 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 in the later stages of pregnancy. Even though external probes have recently been advertised they are highly inaccurate because of the mass of tissue to penetrate. Full bladders are misdiagnosed as pregnancies and other pregnancies are easily missed with these machines. 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 to be practical.  In any pregnancy examination, if accuracy of pregnant versus non-pregnant doesn’t reach 99% it is inadequate.  

With a good internal probe (quality of ultrasounds also varies considerably) besides fetal sexing, twins can be picked up. This is something rarely diagnosed 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 heart beat indicating a dead fetus. 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.

In setting up the ultrasound screen, veterinarians usually need a somewhat shaded and safe area to set up 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. New technology has seen ultrasounds developed with goggles so setting up screens and monitors has become a thing of the past.

As you can see both forms of pregnancy examination have merit. Rectal palpation – being fast and safe – is            commonly done in most herds. With all the equipment being unnecessary, it is also considerably less expensive to do than ultrasonography. Ultrasounds are generally used in problem breeders or when specialized procedures such as fetal sexing is required. Cows being sold with sexed embryos are often reconfirmed in calf by rectal palpation later in their gestation.  Rectal palpation for pregnancy is a procedure done by up to 70 percent 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.