Ask The Vet

Common Causes of Lost Calves

Nutritional deficiencies are just one possible reason for a stillborn calf. (Progressive Farmer image by Victoria G. Myers)


We have had two stillborn calves here in central Texas lately, and I was wondering what causes this problem. The cows are Black Angus heifers. They are on fair to good pasture and are cubed daily with 20% Hi-Energy cubes, and are fed 3 to 4 pounds. They also have a molasses lick trough free-choice at 32% protein. I'm wondering if they are getting too much protein?


An abortion or stillbirth is like a slap in the face for cattlemen. You can see the lost calf and the profit with your eyes. Unfortunately, diagnosing the cause of abortions or stillbirths can be difficult and costly. It is never wrong to investigate these occurrences, but many experts recommend aggressive diagnostics only after loss rates exceed 3 to 5%. Others put that at a more conservative 1 to 2%. It's an operation-by-operation judgment call.

Common causes of loss include calving difficulty and disease (bacterial, viral, fungal and protozoal). Nutritional deficiencies are another common reason for loss.

I doubt excessive natural protein is your problem. Most cubes, tubs and liquid feeds contain nonprotein nitrogen (NPN), typically in the form of urea. This provides nitrogen, which rumen microbes combine with carbohydrates to manufacture proteins. Some lower-quality supplements may contain high levels of NPN.

My question would be whether between the cubes and the lick tanks, your cattle could be taking in too much NPN? Within the rumen, NPN is broken down into ammonia. With low-quality forage and/or hay, rumen microbes may be unable to digest the forage into enough carbohydrate to utilize the ammonia. This can lead to ammonia toxicity.

The first sign seen of ammonia toxicity is often dead cattle. You may see ear twitching, pupil dilation, rapid eye blinking, difficult breathing, excessive salivation, frequent urination/defecation, staggering and convulsions. Some experts feel milder, subclinical cases of ammonia toxicity can lead to abortions or stillbirths. Let me say here, this is very controversial. I bring it up because you ask if your feeding program could be behind these stillbirths, and this would be the only way I could see it. I have my doubts.

If you continue to have these problems, please get with your veterinarian. Begin with a thorough review of your herd health and biosecurity programs. Blood work, including paired serum samples to detect changes in antibody levels, PCR-ELISA (polymerase chain reaction-enzyme linked immunosorbent assay) testing can be helpful. Your veterinarian may want to collect samples of any dead calves or submit the whole body to a diagnostic lab. Try to collect and preserve the placenta, as this is a valuable, often overlooked tissue.