CASE NOTES
Investigating reproductive disease of beef cattle in the pastoral zone - a field clinician's perspective
Scott Parry, Contract DV - Western LLS, Silverback Vet Services
Posted Flock and Herd August 2025
Introduction
Given the inordinate amount of time I have spent loitering around the back end of a cow, rather than any great font of knowledge I possess, I have been asked to present to you today a clinician's perspective of the investigation and diagnosis of reproductive disease in beef cattle in the pastoral zone. So, without further ado, let's make a start.
What constitutes reproductive failure?
Failure to carry a pregnancy to pregnancy testing. Generally evidenced by a lower-than-expected pregnancy-tested-in-calf (PTIC) rate.
- Failure to conceive - disease, nutrition, bull failure
- Early embryonic death (loss of a pregnancy (embryo) prior to 42 days gestation) - disease, toxicity, genetic anomalies
- Abortion (loss of a pregnancy (foetus) after 42 days gestation) - disease, toxicity, genetic anomalies
Failure to bring a calf to branding or weaning. This syndrome can present as a drop off from pregnancy testing to branding/weaning or, in the case of herds that do not pregnancy test, it is just a lower-than-expected branding/weaning rate.
- Abortion
- Dystocia-related deaths
- Neonatal deaths - disease (scouring, BVDV, Lepto), predation, mismothering, environmental
Failure to keep adequate reproductive records
- Poor record keeping makes it difficult to determine if reproductive failure has actually occurred
- Can create the illusion of a problem when one may not actually exist
How do we detect reproductive failure?
At pregnancy testing
- Lower-than-expected pregnancy rates
- Detection of pathology - pyometra, recently aborted cows/heifers, mummified foetuses
- Abnormal conception pattern
At branding/weaning
- Previously PTIC cows showing up dry at branding/weaning
- In non-pregnancy tested herds it is far more difficult to quantify this syndrome. But if an owner has what they consider a lower than (historically) expected branding/weaning rate, it may raise a red flag.
Producer observations of late-term abortion, dystocia, neonatal calf deaths
- Relies on producer vigilance in monitoring calving groups
- In more intensively managed herds producer observation can yield good data and samples
- In more extensively managed herds these sorts of events may not be detected until mustering or when decomposed carcases are found
- Includes disease events such as Akabane with deformed and unviable calves
What level of infertility would trigger an investigation?
This value can be difficult to quantify in a cookie cutter manner.
What level of reproductive failure warrants an investigation varies between:
- Producers
- Veterinarians/advisers
- Type of enterprise - intensive/extensive levels of management
- Type of country - high vs low rainfall, hard vs soft country
- Type of cattle - indicus vs taurus, station bred/self-replacing vs trade mobs, heifers vs cows
- Type of season/nutrition/BCS at joining - reflects energy balance cows are in
Some guidelines I would suggest could be used to trigger a reproductive failure investigation - but these are open to alteration/adjustment for different situations. The exact trigger points can be endlessly debated, but the important thing is that we use SOME objective measurements to identify them.
Reduced pregnancy rate at pregnancy testing:
- <85% (90%?) PTIC to a 12-week joining in well-managed herds in inside-type country on reasonable nutrition
- <75% (80%) PTIC in well-managed herds in more extensively run, harder country
Pathology detected at pregnancy testing:
- Pyometras. Any incidence of active pyometra, in conjunction with a reduced pregnancy rate should trigger an investigation, regardless of enterprise or country. Trichomonas!
- Mummified foetuses & recently aborted females. I have a greater tolerance for these issues than pyometra. However, if 10% or greater of not diagnosed pregnant (NDP) females have a mummified foetus or you suspect have recently aborted, I would suggest some form of investigation.
Pregnancy testing to branding/weaning loss thresholds exceeded
- >5% (7%?) dry cows in well-managed herds in inside-type country on reasonable nutrition
- >7% (10%) dry cows in well-managed herds in more extensively run, harder country
- In non-pregnancy tested herds it is far more difficult to have exact thresholds for this syndrome. Relies a fair bit on “Mabo, the vibe…”
Producer observations of neonatal calf losses, late-term abortions and dystocia issues
- These numbers will be quite rubbery as it is unlikely that all incidences of losses at this stage will be detected/observed and recorded
- Level of detection that begins to approach 5% (3%) of an individual mob would start to raise suspicion that there is an issue that requires investigation
What are our usual differentials for reproductive loss in the pastoral zone?
Always plan to look for horses, but don't forget that zebras do exist as well. Over time, some zebras mutate to horses. I would suggest that Trichomonas has lost its stripes over the past 15 to 20 years.
The usual suspects - the horses
- Leptospirosis
- Vibriosis
- BVDV
- Trichomoniasis
- Nutritional
- Bull failure
- General poor management
The less usual suspects - the Zebras and Przewalski horses
- Environmental and weather-related events - heat, cold, floods etc.
- Arbovirus events - Akabane and BEF
- Neospora
- Management failures - perishing, untimely handling (mustering and yarding)
- Macro and micro mineral imbalances - P, Se, Cu etc.
- Toxicities such as nitrates
How do we investigate these possibilities?
Investigation of reproductive failure in the pastoral zone is often somewhat hamstrung by a combination of:
- Distance and scale of enterprises
- Cost of mustering stock to collect samples
- Nearly always operating retrospectively and the view through the retrospecto-scope is often blurred
- Variable (often limited) amount of good data and numbers to work with. Record keeping is improving with more people using EID and associated software.
The importance of a taking a good history.
The starting point for any disease investigation, including reproductive failure, is to gather as comprehensive a history as possible. A practitioner who has a longer-term, ongoing relationship with a client has a significant head start. If you are doing the pregnancy testing, bull testing and other work for an enterprise, you will have a greater understanding of the operation, its historical reproductive performance, levels of management and biosecurity profile. So many answers can be found in the history.
It is beyond the time constraints of this presentation to set out a comprehensive check list for history taking for these investigations. However, for both LLS and private vets, the use of standardised checklist is useful to standardise history taking and make sure important information is not missed. I assume a lot of practices and LLS offices have such SOPs in place?
- Leptospirosis - MAT on serum, PCR/Histo/Dark field microscopy on body fluids and tissues. Generally test females.
- Vibriosis - ELISA on vaginal mucus detects exposure. Is a herd-level test. Good screening test. Generally test females. Culture on bulls tends to be finicky and you need serial testing to ensure accurate results (tendency for false negatives).
- Trichomoniasis - PCR on bull preputial scrapings works well. Have also detected it in active pyometrons in cows.
- BVDV - AGID testing on females assesses exposure and gives an idea of when it occurred. PACE/Hair testing - detects Antigens/PIs. Other tests available but these are the main ones I use in the majority of investigations. AGID is good to use when animals have been vaccinated - vaccine doesn't affect results, so can still assess natural exposure.
- Various macro- and micro-mineral tests. Liver biopsies arguably better for copper especially, but tend to use serum most of the time.
- Arboviruses, Neospora - antibody ELISA on serum works well for most investigations for screening.
- Bull testing - physical and crush-side testing as well as laboratory-based morphology. Crazy if you don't assess morphology in reproductive failure cases.
- The better understanding you have of an individual enterprise/operation, the better chance you have of getting to the bottom of a reproductive failure problem.
- Good data and a comprehensive history are key to success.
- It is worth having a good look at what data you can gather before launching into a full-blown investigation with thousands of dollars of lab work. A problem may not even exist or may obviously be a management issue.
- Be careful jumping to conclusions based on lab work alone. It doesn't always tell the whole story and people don't always interpret it correctly.
- Laboratory results are useful, even if they come back negative - can rule out a lot of possibilities and help you focus on where to look.
- Northern trade cattle rarely perform as well as people think (hope) they will.
- Everyone wants a silver bullet cure - a virus or a deficiency that can be cured by a single 'magic shot' preferably. The majority of problems are multifactorial and not a deficiency or virus….
Laboratory testing in a reproductive failure investigation. There are a limited number of disease entities that can be practically and economically tested for at a laboratory level. These include:
Interpretation of these results needs to be done with a good understanding of the disease, the tests themselves and the individual situation. This stage is where vets really should “own” the space as they are uniquely situated to cover all of these aspects.
A few final thoughts to leave you with - Parry's pontifications on piss-poor repro performance in cattle.