Abortion outbreaks are often one of the most frustrating and difficult cases for cow-calf producers and veterinarians to deal with.
In many situations, the inciting cause of the problem may have happened weeks or months prior to being discovered, and obtaining a diagnosis at the laboratory can be challenging.
To make matters worse, there is often little that we can do to mitigate the problem in the current year, and we often can only put strategies in place that will prevent the same problem from occurring in future breeding seasons.
I was fortunate to attend a recent seminar by Dr. Yanyun Huang, who is a veterinary pathologist and chief executive officer of the Prairie Diagnostic Services in Saskatoon.
Huang presented some findings from a recent pilot study that he and his team had carried out on fetal abortion cases submitted to the diagnostic laboratory, which was funded by the Beef Cattle Research Council.
The project involved evaluating 48 fetuses from abortion cases in which a diagnostic pathologist did a standard post-mortem, evaluated tissues under the microscope, performed traditional bacterial cultures and evaluated trace mineral and vitamin levels on the fetal liver.
In addition, each of these workups used a next-generation genetic sequencing diagnostic panel known as BovReproSeq. This test allows the pathologist to identify 17 different bacteria, viruses or protozoa that are associated with bovine reproductive failure, all within one test process.
Genetic sequencing could have helped diagnosis rate
One of the most remarkable findings in this pilot study was that using this particular diagnostic strategy provided a category diagnosis in 73 per cent of the cases, with only 13 of the 48 abortion cases going undiagnosed.
An exact cause of the abortion was identified in 62.5 per cent of cases. This is much higher than the diagnostic rate reported in many other studies, which is often in the 40 to 50 per cent range, perhaps partially due to the use of the BovReproSeq test in all these cases.
What was even more remarkable was that if a placenta was submitted in addition to the fetus, 88 per cent of the time a diagnosis was determined, compared to 61 per cent when a placenta was not included.
We have long known that sending a piece of placenta along with the fetus is valuable for abortion cases, but this pilot study proves that the odds of getting a diagnosis are much higher if placenta is submitted to the lab, even when using sophisticated diagnostic testing.
Another interesting finding was the breakdown of the various causes of abortion in these cases.
Infections were still a major cause of abortion, with 44 per cent of the abortions being caused by bacteria and 10 per cent by viruses.
Viruses such as infectious bovine rhinotracheitis virus and various bacteria were identified in 26 of the 48 cases. Congenital causes, nutritional causes and fungal causes made up 10, six and two per cent of the cases, respectively.
One of the novel parts of this study was that the laboratory evaluated the fetal liver for trace minerals and vitamins and was able to obtain a blood sample from the dam to evaluate its trace mineral and vitamin status.
It is important to recognize that these are two different tissues (liver in the fetus and blood in the dam) and so some of the comparisons between the two can be complicated. However, the trace mineral findings in the fetal livers are noteworthy.
The most striking deficiency noted was copper, with 77 per cent of the fetal livers being deficient or marginal.
We have had several studies demonstrating widespread copper deficiencies in Canadian cattle, including from the Canadian Cow-Calf Surveillance Network, and this smaller pilot study has shown a similar trend.
Marginal or deficient levels in vitamin A and E were also common in fetal livers at close to the 50 per cent rate, but this is to be expected because the calf receives a great deal of those vitamins through the colostrum and less via the placenta.
There is a great deal that we can learn from this small pilot study. The value of submitting the placenta is certainly one lesson that we can take home, but it is understandable that obtaining diagnostic material from aborting cows is often a significant logistical challenge for the producer and the veterinarian.
John Campbell is a professor emeritus in the department of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine and is originally from Wingham, Ont.
