Every year near the beginning of spring the whole farm fills with anticipation as the days get longer, the sun shines, and the landscape starts turning green. During the winter months, we work really hard on preparing everything for the spring rush, including our cows! Our cow herd calves in the fall between September and November, so that means that during the winter we have to breed our cows so that they become pregnant. To reference, a cow's gestation length (the time that she is pregnant) is 283 days which is a little over nine months. In general, cows will have a baby every 365 days.
Before our cows are turned out to pasture, we make sure that they are pregnant. This usually happens in late March or early April. We have our veterinarian come out to the farm and pregnancy check “preg check” our cows to see if they are pregnant.
Figure 1: This is how we catch our cattle for pregnancy testing. They get to enjoy their lunch while they are getting checked!
There are three techniques farmers can use to determine if their cows are pregnant. The first is by using a blood test. This can be done when the cow is 30 days in gestation. All the farmer has to do is obtain a blood sample. The blood sample is generally taken from the cow's trailhead between the tails vertebrae. The tail has a coccygeal (tail) vein running through it, so if a cow is restrained in a chute system, this blood test can be easily obtained and is low-stress for the cow. The blood test will measure proteins in the blood given off by the cow's placenta. These proteins are called pregnancy-associated glycoproteins (PAG). Even though this is a good way to diagnose pregnancies, it doesn’t allow us to tell how far along the cows are in their pregnancy, so we don’t use this method.
The second method is a technique generally done by a veterinarian or an experienced technician. The vet will manually “palpate” a cow that is restrained which means they wear a long plastic glove/sleeve on their arm and place their arm in the rectum of the cow. The rectum is directly above the cow’s reproductive tract and the vet can locate the fetus in the uterus from this angle. This practice is also low-stress and causes minimal discomfort to the cows. This method is nice because veterinarians are trained to feel the size of the fetus and can determine the gestational age.
Figure 2: This is a reproductive tract of a cow. The reproductive tract is directly below the cow's rectum.
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Figure 3: This is a plastic glove a veterinarian or a technician uses when palpating cattle.
The third option to check for a fetus is a way we may be more familiar with. An ultrasound machine is also used in cows! This way uses the same process as the second one, but the vet will use an ultrasound machine to detect pregnancy. The vet will place a pregnancy-detecting probe into the rectum of the cow, apply slight down pressure and the uterus will be visible on the ultrasound machine, from here the vet can find the fetus and determine how far along the cow is in gestation. Sometimes, if the fetus is at the right age, a veterinarian can even determine the gender.
Figure 4: An example of an ultrasound machine.
Figure 5: This is an ultrasound image of a baby calf in utero. if you look closely you can see the outline of the calf's head and body.
Figure 6: Another ultrasound image. This picture shows a younger calf in utero than figure 5. If you look in the top left corner your can see the outline of it's body.
For our farm, it is important to pregnancy test our cows using palpation by hand or ultrasound because we use different sires (bulls=males). By the vet telling us how far in gestation the cow is, we can look at the date we bred the cow to determine who the bull was. Future blog posts will explain our breeding process in more detail. Once the cows are checked pregnant, we will group them based on how far along in pregnancy they are. Those pregnancy groups can then be moved to different pastures for the grazing season. We group the cows this way so that when it is time for them to have their babies we can easily concentrate on the cows that are due versus watching cows that aren’t as far along in their gestation (there is a three-month difference in fetuses' ages in our cow herd)
The cows that are not checked pregnant in our herd will either be grouped and have an opportunity to be bred by a bull so that we can sell them to another farmer to be part of their spring calving season, or they will be fed a higher energy feed so that they gain weight and can be sold as a cull cow. This is the term that the livestock industry gives to breeding animals who are older or don’t become pregnant and that are sold for slaughter. They are very important to the livestock industry as a whole. If these animals are not bringing in the farmer any money, they essentially “change careers” and will be sold to provide meat for people to eat.
Thank you!
Olivia, Tabby, Gina, & Kendra