4 minute read
Herd Health
Both rectal palpation and ultrasound 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 to outline the pros and cons of each method so you can see how best they fit in your farming operation. Many myths and fallacies surround pregnancy examination and hopefully these will be dispelled in this article.
Rectal examination has 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 (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 minutes 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 things are 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. 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, 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. One must keep in mind abortions still normally occur in 2‐3% of cattle yearly. This has numerous causes including genetic defects, infectious causes, twinning and trauma. The veterinarian relies on a good set up of equipment, 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 and retract to confirm an open uterus.
Ultrasound 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 more inaccurate in the later stages of pregnancy. Newer ultrasounds have probes that get much deeper so allow more accuracy later in pregnancy. Others have introducers whereby the veterinarian’s arm does not even enter the rectum. We need to watch these as occasionally the rectum can be perforated and a massive peritonitis is the result. Vets use lots of lubricant if using the probe introducer. Fine feel and gentleness are a virtue when it comes to rectal palpation. In inexperienced hands full bladders are misdiagnosed as pregnancies and other pregnancies can be missed. Veterinarians would have gladly embraced this concept since rectal palpation is really hard on shoulders and elbows. In any pregnancy examination, we must strive to be 99% plus in the pregnant versus non‐pregnant department.
With a good internal probe (quality of ultrasounds also varies considerably) besides fetal sexing, twins can be picked up and this may help the producer manage these cases differently. Fetal sexing is impossible manually and twins will rarely be picked up. Again though, cows must be ultrasound 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 veterinarian can explain.
As you can see both forms of pregnancy examination have merit. Rectal palpation being fast and safe is commonly done in most beef herds. Without all the equipment being necessary it is also 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. Pregnancy checking is done by upwards of 70‐80 percent plus of cattlemen across Western Canada, but it should be much higher when we think of the feed costs this saves or being able to identify problem breeders earlier. It is even more critical as far as purebred cattle are concerned with more dollars tied up
