WHAT ARE YOU DOING IN THERE? WHAT PALPATION ENTAILS.
Pregnancy diagnosis via digital palpation or ultrasound is a key component to any farm’s reproductive program as getting cows pregnant in a timely and consistent manner drives the future production of the dairy. Some may wonder, “What is the vet actually doing in there to find a pregnancy?”
There are four cardinal or diagnostic signs of pregnancy that if felt or seen assure us the animal in question is pregnant.
1. Amniotic Vesicle -associated with the calf, the amniotic vesicle is a thin, tough, membranous sac that encloses the embryo or fetus. This vesicle can be felt up until around 50-70 days.
2. Fetus -associated with the calf, around 50-70 days the fetus can be felt through the vesicle and can be felt for the remainder of the pregnancy. Often, however, during months 3-6 the calf is too deep into the abdomen and too far over the pelvic brim to feel. On ultrasound, the developing fetus can be seen before 30 days.
3. Fetal Membranes -associated with the placenta/cow, the fetal membranes are the chorio-allantoic membrane of the placenta and can be felt through the uterine horn at around 30 days bred and up.
4. Placentomes -associated with the placenta/cow, placentomes form inbetween the uterus and the fetal membranes to supply the growing fetus with blood and nutrients. These can be seen on ultrasound developing as early as 45 to 50 days, and begin to be felt on palpation around 75 to 80 days.
Along with the cardinal signs of pregnancy, there are associated signs of pregnancy. Associated signs of pregnancy will always be present in pregnant cows, but may be present in non-pregnant cows. Therefore, they are only supportive evidence of pregnancy and not diagnostic.
1. CL - Progesterone is essential to the health and continuation of the pregnancy and is produced by the CL or corpus luteum.
2. Fluid - The fluid is inside the chorioallantoic membrane and surrounds the calf.
3. Fremitus – Fremitus can be felt in the middle uterine artery. This artery runs in the broad ligament (which holds the uterus in place) and can be palpated. One of my professors always told us fremitus feels like a hummingbird looks. This tells us that there is good blood supply to the uterus to support the pregnancy.
So in short, we are looking for (ultrasound) or feeling for (palpation) the amniotic vesicle, the fetus, the fetal membranes, or the placentomes. We may also assess the ovary for a CL, the fluid in the uterus, and the middle uterine artery to support the diagnosis of pregnancy and determine the age of the fetus.