The author, from Orefield, Pa., is a veterinarian with a master of business administration degree (MBA). He is a business development manager with Cargill Animal Nutrition Consulting Services.

I had two cows abort last week. What do you suppose is going on?"

That question comes up several times a year. Of course, the significance of two abortions depends on the size of the dairy. In any size herd, the economic loss associated with abortion is huge.

The term "abortion" usually means the death and expulsion of the fetus more than 42 days since conception. Lost pregnancies before that time are called "embryonic deaths." If pregnancy diagnosis is done early, around 30 days, we can expect that approximately 10 percent of all cows that are confirmed pregnant will lose that pregnancy before a full-term delivery. Roughly half will occur 12 days past a 30-day reproductive exam and half after that time. If we delay pregnancy diagnosis until later, then the number of lost pregnancies will appear to be lower, simply because many of the ones destined to be lost will never be diagnosed in the first place.

There is a great deal of variation in abortion rates between herds and within the same herd from year to year. I have observed smaller herds going a couple of years with no abortions and then have three or four within a few months. Our efforts to diagnose the cause of these abortions often come up empty.

What are the causes?
Individual cows can abort for a wide variety of reasons. A genetic defect in the fetus or secondary stress due to a systemic illness are two possibilities. When there are higher incidences in a herd, then we are usually dealing with either infectious disease or some type of toxin. Severe heat, overcrowding, or other stress factors may also affect enough animals to create a herd problem.

Common diseases that cause abortions include bovine viral diarrhea (BVD), infectious bovine rhinotracheitis (IBR), leptosporosis, and neospora. Vaccines can protect your herd against these agents. Work with your veterinarian to establish and administer a sound vaccination program. Be aware that some vaccines or combinations of vaccines may actually induce abortions. Toxins include nitrates and certain types of mycotoxins.

Making a definite diagnosis of the cause behind abortions can be extremely frustrating. By the time the fetus is expelled, it is often decomposing, making testing of tissues difficult.

However, our best chance of getting an answer still lies with submitting the aborted fetus to a diagnostic lab, along with some of the placenta. Blood samples from the dam, other cows that have recently aborted, and a few nonaborting herd mates should also be submitted. Even with all these samples, a definite diagnosis will be attained less than half of the time.

The best way to minimize your abortion rate is to follow sound protocols that will maximize herd performance and profit overall. These include minimizing stress by having good ventilation and cow comfort. Avoid feeding moldy feed or drought-stressed crops that may have high nitrate levels. Test if you are not sure.

Follow a sound vaccination program. Keep cows clean. Provide a well-balanced ration with adequate vitamins and minerals. Keep good records so that you can recognize if and when your abortion rate changes.

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