How does a rancher know if the cows are pregnant? This information is very handy to know, since a pregnant cow makes the product that a rancher hopes to sell in the fall (the calf). To determine if she is pregnant, typically the rancher hires a veterinarian to come and “preg check” his cows to determine if they are pregnant or not. While there are blood tests that can say if a cow is bred, an older, but more effective way to determine pregnancy status is through rectal palpation. Simply put, as a vet I stick my arm in a cow’s behind and feel her uterus for a baby.
If you are a dazzling urbanite, you may ask yourself, “Why on earth would this be the preferred method? Do you like playing in poop, Jake?” For starters, no I don’t, but it does amazing things for your skin complexion. Second, it is the preferred method because of two reasons. 1) Cows have very thick skin, so trying to just slap an ultrasound on their belly like what happens with women would not work. 2) You can actually feel the baby so closely this way that you can tell how old the baby is. It is a safe practice for the baby and the mother cow.
Preg checking by rectal palpation is accomplished by gently guiding a lubricated hand into the rectum. Like the picture below illustrates, the veterinarian feels the uterus for signs of pregnancy. This includes the fetus, the vesicle the fetus resides in, the “buttons” (the $10 word for them is ‘cotyledons’) that are part of the placenta, or the amniotic membrane slipping between your fingers. Based on the size of the fetus or the buttons, the approximate age of the fetus can be determined. If you want to get more exact, an ultrasound probe can be taken into the rectum with your hand and be used to age the baby down to the exact day.
Once the cow is determined to be bred or open (not pregnant), the rancher can make a decision on how to manage her for the next year. And in case you are wondering, those green manure stains are a real bugger to get off your jeans. Wear coveralls.