The biggest driver of profitability on any commercial cow-calf operation is reproduction, and more and more producers’ cow herds are experiencing problems with abortions.
Historically, the main culprit for abortions were diseases such as persistently infected BVD (bovine viral diarrhea) and leptospirosis. However, producers today are seeing increasing early-term abortions from recessive genetic defects as well as mid- to late-terms abortions from the protozoan parasite, Neospora.
Neosporosis is a relatively new problem, having only first been reported in a dairy herd in 1987. It has since spread into the beef industry. SEK Genetics did a survey of 5,800 beef cows in the Arkansas, Kansas, Missouri and Oklahoma region and found 8.9 percent positive for Neospora protozoa. Positive cattle will breed up at a normal rate but can abort up to 50 percent of their fetuses. There is no vaccination, and other than the higher rate of abortion, positive cattle generally show no other negative effects. Therefore, the only way to identify them is through testing.
The definitive host for the parasite is canines such coyotes, foxes and dogs. However, cattle are intermediate hosts and can become infected by consuming canine feces. If not aborted, 90 percent of progeny of Neospora-positive cows will be carriers of the parasite. According to Dr. Don Coover of SEK Genetics, this is how the majority of cattle contract it.
“The passing of the protozoa parasite from dam to progeny is what we refer to as vertical infection, while those that catch it from canine feces is horizontal infection,” Dr. Coover relates.
“Having tested thousands of cattle, we see very little horizontal infection, though it certainly happens. This means that herds with positive cattle can usually be cleaned up through testing and culling.”
Dr. Coover described a case study of effective testing: “Recently, we helped a producer blood test one of his herds for pregnancy status back in March. Most of the cows in this herd were 90 days or more into gestation when tested. The producer took the 121 pregnant cows in the group and moved them to a different pasture for the summer. He noticed a few cows showing estrus and decided in late June to see how many had lost their pregnancies. He again pulled blood samples on all 121 cows, and we retested all the cows for pregnancy status. Seven turned up open, a 6 percent pregnancy loss rate.
“After some discussion—ruling out other likely causes of pregnancy loss—he asked us to test the seven cows that lost the pregnancies for Neospora infection, and all 7 were seropositive, indicating they were all chronically infected. He then told us to test the other 114 cows in that group for Neospora infection, and 6 more were seropositive, for a total of 13 Neospora-positive cows out of 121—an 11 percent infection rate. Seven out of 13 Neospora-positive cows had aborted (or 54 percent of the Neospora-positive cows) and none of the 108 Neospora-negative cows aborted.”
The test is approximately $5 per head, so it is affordable. Dr. Coover gives the example that for a 100-cow herd their data indicates typically 9 percent can be expected to be positive. Of the nine positive cows, at least three can be expected to abort, which is a significant financial loss. With the test at $5 per cow, the cost to test the 100 cows is $500, so the test will pay for itself. Once a herd is clean, in Dr. Coover’s experience, all that is needed is to test heifers introduced from outside the herd to keep it clean.
Another less extensive way to cleanup a herd is to test any cattle that turn up open after pregnancy checking. It is important with any positive cattle that their dams then be tested to eliminate vertical infection.
In addition, producers marketing replacement heifers are also recommended to test for both Neosporosis and persistently-infected BVD (PI-BVD). It is insurance that a producer is marketing a top-quality product that doesn’t introduce problems into their customers’ herds.
Dr. Coover also emphasizes the need for seedstock producers to test recipient cows in an embryo transfer program.
“Producers doing embryo transfer are dealing with high-price genetics. Often the recipients are poorly identified as to their background, so it pays to test them. It is important to note that calves born alive from Neospora-infected recipient cows have a 90 percent chance of being positive themselves. For $5 a test, this is an unnecessary risk.”
Avoiding abortions in commercial herds is becoming ever more important with a number of genetic conditions, diseases like persistently-infected cattle for BVD, and now Neospora, that will all cause abortions. To make money in the commercial cow-calf business starts with a live calf. Therefore, all cost-effective “tools in the toolbox” that will result in a higher percent calf crop weaned should be employed by producers.
Dr. Coover sums it up, “There is a lot of things that can cause abortions in beef cattle but cleaning a herd up for Neosporosis is low hanging fruit.” — Dr. Bob Hough
