A calf is born dead. The cow needed assistance. The calf was big.
Case closed?
Maybe not.
A difficult birth is an obvious place to look for answers, but it isn’t necessarily the whole story. A calf can die around birth for reasons that aren’t immediately apparent from the calving itself. Sometimes the clues are in the cow’s history. Sometimes they’re in the circumstances surrounding the birth. Sometimes they aren’t visible until the calf is examined after death.
Recent beef cattle research is taking a closer look at those clues. When a calf is born dead, how much can we learn by looking beyond the calving event?
Stillbirth Risk Varies Across Beef Herds
One place to start is with the herd itself.
Researchers studying Japanese Black cattle analyzed 94,569 calving records from 24,821 cows across 1,001 farms in Kyushu. The overall stillbirth rate was 1.91%, giving the researchers enough data to look for patterns that might be difficult to see in an individual herd or a handful of calvings.
Several factors stood out:
- First-calf cows had greater stillbirth risk than cows in later parities.
- Winter calving was associated with higher risk.
- Previous stillbirth was associated with recurrence.
- Herd size was associated with stillbirth, with smaller herds generally showing lower rates.
- Sire also appeared to influence risk, with noticeable differences among individual sires.
The previous-stillbirth finding could be particularly useful in practice. A cow that has already lost a calf may warrant more attention during her next calving rather than having that loss treated as an isolated event. The researchers specifically suggest enhanced calving management for these animals and considering previous stillbirths when making replacement decisions.
The sire finding is more complicated. Stillbirth had a heritability estimate of just 0.037, meaning additive genetics accounted for a relatively small portion of the overall variation. The researchers therefore emphasized environmental management as the primary opportunity for reducing losses.
Still, individual sires did not all look the same. Of 43 major sires evaluated, seven had stillbirth rates more than one percentage point above the overall 1.9% average, while 13 were more than one point below it.
Genetics may not determine the outcome, but they may shift the odds.
Dystocia Doesn’t Explain Every Calf Loss
The next question is harder to answer: What actually killed the calf?
A 2020 study of beef herds in Orkney approached perinatal mortality from that direction. Researchers collected calving data from 11 herds, covering 1,101 calves, while 23 herds in total contributed calves for postmortem investigation.
Among the 54 calves submitted for investigation, researchers reached a definitive diagnosis in 85% of cases. Parturition-related death was the largest category, accounting for 20 calves. But the investigators also identified 13 intrauterine infections, six congenital malformations and six postpartum infections.
However, all of those calves ultimately end up in the same broad category: perinatal loss.
The circumstances of birth also mattered. Male calves had 2.5 times the odds of perinatal loss compared with females, while twins had 3.5 times the odds of singletons. Births requiring hard assistance, veterinary assistance or cesarean section had 3.2 times the odds of loss compared with unobserved births.
The postmortem findings add another layer. Among the parturition-related deaths, investigators found evidence of bradytocia, trauma, malpresentation and twin birth. The intrauterine infections included Bacillus licheniformis, Aspergillus species, Aeromonas hydrophila, E. coli and Leptospira hardjo.
Dystocia clearly remains an important pathway to calf death, but this work makes it harder to treat dystocia as the default explanation for every loss.
Genetics May Shift Calf Mortality Risk
The Japanese study raises another question. If individual sires differ in stillbirth rates, what is behind that variation?
A large Irish genomic study provides some context. Researchers examined Angus, Charolais and Limousin sires representing 5.87 million calving events and identified genomic regions associated with direct calving difficulty, maternal calving difficulty and perinatal mortality. Most of the associations were breed- and trait-specific.
Some of the strongest signals involved the myostatin (MSTN) gene region in Charolais and Limousin cattle. But MSTN wasn’t the whole story. The researchers identified multiple genomic regions associated with calving difficulty and perinatal mortality, with most of the genetic variation appearing to come from many variants with relatively small effects.
The Charolais results offer an especially interesting wrinkle. Several genomic regions remained associated with perinatal mortality after researchers accounted for genetic merit for direct calving difficulty. SCN4B, a gene related to sodium channel location and function, emerged as a novel candidate associated with perinatal mortality but not dystocia.
That doesn’t mean there is a simple set of “stillbirth genes.” The Japanese study’s low heritability estimate argues against that. Instead, the findings suggest that genetic risk for calf mortality can involve more than the genetics of an easy or difficult birth.
Look for Patterns After a Stillbirth
None of these studies produces a single formula for preventing stillbirth. What they offer is a reason to pay closer attention to patterns that can disappear when every loss is simply recorded as “stillbirth.”
When investigating a loss, useful questions might include:
- Has the cow experienced a previous stillbirth?
- Are multiple losses occurring in the same herd?
- Are losses associated with a particular sire?
- Did the calf die despite an apparently normal calving?
- Did the calf have unusual physical abnormalities?
- Are losses clustered by season or parity?
- Is there evidence of infection rather than trauma or anoxia?
The answers won’t necessarily point to one cause. They can help determine whether a loss looks isolated or whether it belongs to a larger pattern that deserves a closer look.
