Reproductive efficiency is central to herd health, productivity, and economic sustainability in large animal systems. When infertility, pregnancy loss, or abortion occurs, veterinarians must identify the underlying cause to prevent further reproductive losses and protect overall herd health.
In a recent podcast episode of Diseases and Diagnosis, produced by the Texas A&M Veterinary Medical Diagnostic Laboratory, TVMDL, veterinary diagnostician Semira Mancill, DVM, DACT, discussed diagnostic approaches for large animal reproduction.
A multifactorial clinical challenge
In large animals, reproductive failure and abortion are rarely attributable to a single cause. Multiple factors should be considered, including estrous cyclicity, conception success or early embryonic loss, and evidence of disease. In addition, influences related to management, nutrition, and toxicity should also be investigated.
“With these factors in mind, a targeted diagnostic plan should be formed,” Mancill said.
The role of TVMDL in large animal reproduction
TVMDL plays a critical role in investigating reproductive issues by offering tools that assess both parental and offspring factors.
“We want to test both the maternal side as well as the fetal or placental side,” Mancill said. “And the sire’s infertility is certainly an important factor not to be overlooked.”
Maternal and paternal diagnostic evaluation may include serology, hormone profiling, and microbial culture swabs to assess endocrine function and infectious disease status, while fetal and placental tissues can be examined using histopathology, PCR, culture, and toxicologic testing.
By combining these diagnostic tools, veterinarians can more confidently pinpoint the cause of reproductive problems and guide decisions that protect animal health and improve herd outcomes.
Sample collection: Maximizing diagnostic yield
Accurate diagnosis begins long before samples reach the laboratory. Proper sample collection, labeling, and documentation are essential to maximizing diagnostic yield.
When submitting a sample, providing an accurate and thorough case history is vital. Key details can make a significant difference in the lab’s ability to interpret results accurately, including:
- Species and breed
- Gestational age
- Reproductive history
- Vaccination history
- Relevant herd trends
“It is also best practice to ensure the samples provided meet requirements for the desired tests and that any cross-contamination is avoided,” Mancill said. “The TVMDL test catalog provides in-depth information on sample types for each test.”
Careful preparation and documentation give the laboratory the best chance to provide precise, actionable results.
Abortion panels
One of the most valuable resources available through TVMDL is the large animal abortion panel, offered for cattle, sheep, and goats. These panels are designed to detect common infectious causes of abortion and typically combine pathology, microbiology, molecular diagnostics, serology, and, when indicated, toxicology. The specimen required for submission varies depending on the specific panel selected.
Common pathogens tested in large animal abortion panels include:
- Brucella spp.
- Leptospira spp.
- Neospora caninum
- Bovine Viral Diarrhea Virus (BVDV)
- Herpesviruses
- Chlamydia spp.
- And other relevant infectious agents
Pregnancy confirmation across species
TVMDL also supports reproductive management through lab-based pregnancy diagnostics. In cattle and several ruminant species, pregnancy can be confirmed by detecting pregnancy-specific binding protein (PSBP) using an ELISA assay on serum or plasma. This non-invasive test is validated in cattle, sheep, goats, and numerous wildlife and exotic ruminants, and can detect pregnancy as early as 28 days post-breeding in some species.
For horses, pregnancy testing is offered through several hormone-based assays. Measurement of equine chorionic gonadotropin (eCG) is most reliable between days 50 and 100 of gestation and is particularly useful when ultrasound is unavailable.
Estrone sulfate testing, reliable after 60–90 days of gestation, can be complemented by equine pregnancy panels that include progesterone to further enhance diagnostic accuracy.
Male reproductive evaluation: Testosterone testing
Assessment of the sire is a critical, and sometimes overlooked, component of reproductive diagnostics. Testosterone testing can help identify reproductive tissue in geldings suspected of being cryptorchid and explain unexpected stallion-like behavior.
“The test may be performed as a baseline measurement or as part of a dynamic endocrine evaluation using human chorionic gonadotropin (hCG) stimulation,” Mancill said. “The hCG stimulation test is often preferred over a single baseline measurement because it increases diagnostic accuracy by challenging the endocrine system and revealing functional tissue that might not be apparent with baseline levels alone.”
In cases where testosterone results are equivocal, alternative assays such as anti-Müllerian hormone (AMH) testing may be recommended.
Key takeaways
Large animal reproductive diagnostics are inherently complex, with causes of infertility, abortion, and pregnancy loss often spanning multiple factors in both the dam and the sire. While abortion panels, pregnancy confirmation assays, and testosterone evaluation provide critical insights, they represent just a portion of the broader diagnostic toolkit.
“Good breeding soundness exams on males and females may identify issues beyond hormone and infectious disease testing,” Mancill said. “Examining semen quality is vitally important as well.”
Overall, thoughtful, integrated reproductive diagnostics empower veterinarians to address underlying issues, optimize interventions, and ensure healthy, productive herds.
Clients seeking detailed guidance on reproductive diagnostics can visit tvmdl.tamu.edu or call the College Station laboratory at 888.646.5623 or the Canyon laboratory at 888.646.5624 to consult with a veterinary professional.
