Today is the day. You will find out if all of your hard work has paid off. You’ve been diligent in your preparations. You’ve followed the protocols to a T. You’re excited and yet nervous. You hope for the best and, still, you prepare yourself for the worst. Then, the verdict comes in. The cow is … open. Ugh! It’s a moment of utter frustration! You shake your head in disbelief and wonder why, when, how?
Reproductive efficiency on a dairy is an important factor in overall profitability, and a sizeable amount of labor is involved in the synchronization or estrus detection and insemination
of cows and heifers. That is why an open cow at pregnancy check is so frustrating. Time, money, and other resources have resulted in a negative note on the checklist.
A frustration I have heard voiced several times is not knowing when or why cows lose pregnancies. Unfortunately, the list of possible whys is long and, more than likely, somewhat specific to your farm’s location, climate, etc. What we can narrow down a bit, is the WHEN.
Common Methods of Pregnancy DetectionThe rate of pregnancy loss is variable among farms, as is the method of pregnancy detection used. There are several methods of pregnancy detection employed on progressive dairy operations including:
• Monitoring cattle for return to estrus
• Rectal palpation
• Ultrasound
• Blood or milk sample to test for pregnancy
associated glycoproteins (PAG)
When are Embryos Most Likely to Die?
Timelines and reasons for embryonic loss are variable, with lactating dairy cattle representing a unique niche of cattle suffering from prolonged periods of embryonic and fetal loss.
Generally speaking, embryonic loss occurs from fertilization to day 42 of gestation, and fetal loss occurs from day 42 of pregnancy to calving (Nomenclature, 1972). The rate of embryonic loss is debated, but it has been estimated that up to 40% of embryonic loss occurs before day 15 of
gestation (Thatcher et al., 2001; Berg et al., 2010). A recent study reports a 5-10% loss between 14 and 18 days of gestation, and an additional 5-10% loss from days 29 to 42 of gestation (BonDurant, 2007).
When to Check for Pregnancy?
With those numbers in mind, the next question is, when is the best time to pregnancy check? The goal of an efficient pregnancy detection system is to identify open cows as soon as possible, so they can be rebred in a timely manner. The strategic scheduling of pregnancy checks, and if applicable, the continued tail chalking of pregnant pens, can assist in locating open cows sooner.
The first pregnancy check is focused on detecting the cows that are open following an insemination. We know that the majority of embryonic deaths occur before a pregnancy check is possible (less than 25 days), so the sooner the first pregnancy check occurs, the sooner cows can be re-inseminated. This
typically means between 30-40 days post-insemination for a palpation or ultrasound herd, but can be as quick as 28-29 days if chemical pregnancy tests are implemented.
The second pregnancy check should be focused on finding cows with embryos that were lost between the first pregnancy check and approximately 65 days post‑insemination. Research shows that the rate of embryonic death is still continuing to decrease sharply between days 42 and 56 post-insemination,
but levels off and decreases by only a few percentage points from days 56 to 98 (Santos et. al., 2004). The placenta is also beginning to form functional placentomes (the placental connection between the fetus and the uterus) around day 42 of pregnancy, which is attributed to lower risk of embryonic loss.
While gaining a better understanding of when cows and heifers experience pregnancy loss may not quite erase the frustration upon hearing the word “open” at pregnancy check, it may make you feel a little better knowing there’s statistical analysis regarding when loss occurs and when pregnancy checks are most beneficial.
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