The middle of summer is not the time when many cattle producers think about pregnancy testing. However, for producers that have yearling heifers that were bred early this spring, many of those heifers are far enough along to be pregnancy tested.
The minimum length to identify a positive pregnancy diagnosis is approximately 26 to 30 days post breeding utilizing either an ultrasound machine or a blood test. The minimum length to identify pregnancy through rectal palpation requires that heifers be at least 35-45 days post breeding.
Potential Advantages of Early Pregnancy Diagnosis
• Heifers that are not pregnant can be identified and managed differently than their pregnant herd mates.
• Non-pregnant heifers that are going to be retained can be implanted, improving average daily gain and feed efficiency.
• Non-pregnant heifers could be moved off grass resources and sold.
• Historically July, August and September are seasonally strong markets for feeder cattle, with prices tending to trend down in the fall. Early identification of non-pregnant heifers allows for selling into this market.
The best method for early pregnancy diagnosis will vary based on goals, costs and resources available. A combination of methods may be used under some circumstances to identify pregnancy.
For example, consider a group of heifers that were artificially inseminated and then exposed to a clean-up bull for 30 days. Pregnancy testing 30 days after the bull was removed would mean heifers that conceived to artificial insemination on the first day of the breeding season would be 60 days along. Heifers that conceived on the last day of the breeding season to the bull would only be 30 days pregnant. Heifers that conceived early in the breeding season could easily be identified with palpation. Those that conceived late in the breeding season would require either a blood test or ultrasound in order to be confirmed as pregnant.
In this situation, if palpation was being used to identify pregnancy, heifers identified as not being pregnant could have a blood sample drawn while still in the chute and sent off for analysis to verify the non-pregnant designation. It is likely that some of the heifers that were identified as non-pregnant through palpation are indeed pregnant, but are not far enough along to be recognized. The blood test would identify which heifers were non-pregnant and which are very early on in their pregnancy.
There are a number of blood test options available on the market today. The following are three that are currently available.*
• IDEXX Bovine Pregnancy Test and Rapid Visual Pregnancy Test
Potential Disadvantage of Early Pregnancy Diagnosis
Producers should realize that stress to heifers early in pregnancy can result in embryonic loss. Research has shown a pregnancy loss of 1-3.5% when palpation or ultrasound are used for pregnancy diagnosis at 40 - 75 days of gestation.
Currently, this author is not aware of any studies that have evaluated the incidence of pregnancy loss using blood testing compared against either palpation or ultrasound for early pregnancy diagnosis. The stress of handling cattle through the chute with blood testing for pregnancy diagnosis could also contribute to early embryonic loss.
In conclusion, early pregnancy diagnosis can provide opportunities to improve profitability. It has some risks associated with it in terms of potentially causing early embryonic loss. Evaluating all of the potential costs and benefits of early pregnancy diagnosis can help producers evaluate whether or not to utilize this in their operations.
For more information on the potential advantages and risks of early pregnancy diagnosis see the web video “Early Pregnancy Diagnosis” (http://beef.unl.edu/early-pregnancy-diagnosis).
*Identification of names of blood test options for pregnancy diagnosis in this article is not intended to imply recommendation or endorsement of these products.