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. Either method of preg checking has it pros and cons, and producers need to know there are a few myths that need to be dispelled.
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 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 good setups and by skilled veterinarians, hand-checking rates of up to 100 head per hour can be accomplished. A false belief that pregnancy examination causes abortions is one we still hear frequently. There is only a very slight risk in the very 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 is often claimed. 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.
Proper equipment simply refers to 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.
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.
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 to slow. In any pregnancy examination, if accuracy of pregnant versus non-pregnant doesn t reach 99 per cent 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 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 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 an area somewhat shaded that is safe for equipment placed 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.
PROS AND CONS
As you can see, both forms of pregnancy examination have merit. Rectal palpation being fast and safe is commonly done in most herds. 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.