Confirmation of pregnancy is a crucial aspect of managing beef cattle herds, especially to determine whether females are pregnant to artificial insemination (AI) or for culling purposes. Early and accurate identification of pregnant cows allows producers to make informed decisions that enhance reproductive efficiency and overall herd productivity. 

Among the various methods available, blood-based pregnancy detection has gained popularity due to its accuracy and ease of use. This article explores some common blood-based pregnancy tests on the market, what they measure, their effectiveness and the positive and negative aspects of these methods.

Several blood-based pregnancy tests are available for beef cattle, each with its unique features and benefits. Some common types, but not fully inclusive of all available tests, to producers include:

1. The initial blood pregnancy tests, such as BioPRYN^®, to enter the market were associated with detection of pregnancy-specific protein B (PSPB) in the blood of cows. Production of PSPB is by the placenta and can be detected as early as 30 days postbreeding.

2. Recent versions of blood-based pregnancy detection methods, such as Alertys OnFarm or DG29^®, detects pregnancy-associated glycoproteins (PAGs) in the blood. Production of PAGs is also by the placenta and can be detected as early as 28 days postbreeding. 

These proteins are produced by the placenta and are present in the blood of pregnant cows. The presence of these proteins indicates the cow is pregnant, while their absence suggests the cow is not pregnant.

Effectiveness of blood-based pregnancy diagnosis tools

Blood-based pregnancy tests are highly effective and accurate. Research has demonstrated sensitivity of the tests is usually 100%  or close to 100% accurate, whereas specificity exceeds 85% in detecting pregnancy in dairy cows. This means the tests are highly accurate at detecting nonpregnant cows. 

In some cases the tests may have false positives where the test will indicate a cow is pregnant, when in fact she may not be pregnant.  These false positives tend to be associated with females that were likely pregnant, but have undergone embryonic death or are in the process of undergoing embryonic death. Regardless, producers should have high confidence that the results effectively determine whether a female is not pregnant, with close to 100% accuracy, especially for determining pregnancy early in gestation.

Positive aspects of blood-based pregnancy detection methods

1. Accuracy: Blood-based tests are highly accurate, providing reliable results that help producers make informed decisions.
2. Early detection: These tests can detect pregnancy as early as 28 days postbreeding, allowing for early identification of pregnant cows.
3. Ease of use: Blood-based tests are relatively easy to administer. Producers can collect blood samples themselves and send them to a laboratory for processing or use chuteside tests for immediate results.
4. Noninvasive: Blood-based tests are less invasive compared to rectal palpation and ultrasound, potentially reducing stress on the animals.

Negative aspects of blood-based pregnancy detection methods

1. Cost: While blood-based tests are generally affordable, the cost can add up, especially for large herds.
2. Wait time for results: Laboratory-based tests require a few days for processing, which may delay management decisions. However, chuteside tests like Alertys OnFarm Pregnancy Test provide immediate results.
3. False positives: Blood samples collected too soon after calving may result in false positives due to residual PAGs from the previous pregnancy. It is advisable to only use blood-based pregnancy tests in cows at least 70 days after calving to ensure that residual PAGs from the previous pregnancy do not result in false positives.

While blood-based pregnancy detection methods offer significant advantages for livestock producers, they should not be viewed as a replacement for the expertise and comprehensive care provided by veterinarians. 

First and foremost, veterinarians bring a level of diagnostic skill that extends beyond simply confirming pregnancy. They are trained to recognize a variety of reproductive and general health issues that may be present but undetectable through a blood test alone. For example, a cow may test positive for pregnancy, but a veterinarian can also assess the animal’s overall reproductive health, identify signs of infection or abnormal uterine conditions and recommend timely interventions.

Additionally, veterinarians play a vital role in herd health management and biosecurity. Their routine visits allow for the early detection of contagious diseases, provision of vaccinations and implementation of herd health protocols that extend beyond reproduction. 

Relying solely on blood-based tests eliminates valuable opportunities for veterinarians to observe and address other health concerns during regular herd checks, potentially leading to missed cases of illness or suboptimal herd performance.

Another consideration is that blood-based tests, while accurate, are not infallible. Issues such as improper sample collection, handling errors or testing during the incorrect postpartum window can lead to inaccurate results. Veterinarians are equipped to interpret ambiguous results, retest as necessary and provide guidance on best practices for sample collection and timing. Their involvement helps producers avoid costly errors and ensures that reproductive management decisions are based on sound, holistic understanding.

The veterinarian-client relationship fosters ongoing education and support. Veterinarians advise on nutrition, breeding practices, calving management and animal welfare, all of which are critical to maintaining a productive and healthy herd. In summary, blood-based pregnancy detection methods offer a reliable and efficient way to identify pregnant cows early in gestation. 

With various types of tests available, producers can choose the one that best suits their needs. While these tests have many positive aspects, such as accuracy and ease of use, they also have some drawbacks, including cost and potential false positives. Chuteside methods provide quick and convenient options for pregnancy detection, allowing producers to make timely management decisions. These tests should complement — not replace — the indispensable expertise of veterinarians in our cattle operations.  

Editor’s note: Cliff Lamb is the animal science department head and a professor at Texas A&M University in College Station, Texas.