Ask the Vet

By Dr. Ken McMillan, Contributing Columnist

READER: 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?

DR. McMILLAN: 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.

READER: Would you please explain any risks of feeding mature wheat hay to cows?

DR. McMILLAN: Wheat can make excellent hay. Cut in the boot to very early head-emergence growth stage, it can have a high nutrient content. Yield may be increased by waiting until early milk stage of the grain, but it will be lower in quality. I recommend forage testing as a quick, easy way to assess quality. It will help you decide if supplements are needed based on the life stage of cattle you're feeding.

There are concerns with wheat hay. Always ask why the wheat was cut for hay and at what stage. I'd be concerned if this were drought-stressed wheat harvested for hay as a salvage measure. High temperatures, low moisture and low relative humidity (especially if combined with high nitrate fertilization) can cause nitrate concentrations to build up in plants. If there is any concern about nitrate toxicity, testing is advised. Also, consider that some fungicides, insecticides or herbicides may have restrictions on grazing and forage use.

Lastly, remember there are many varieties of wheat. Some were developed for grazing, hay or silage, but most are grown for grain. Those varieties developed for grain production have rough awns to aid in harvesting. These rough-awned varieties may cause soreness and irritation to the mouth, lips, gums and lower surfaces of the tongue in cattle. Ensiling rough-awned varieties can reduce this problem, as can harvesting at the late-boot stage rather than the dough stage.

Please contact your veterinarian with questions pertaining to the health of your herd. Every operation is unique, and the information in this column does not pertain to all situations. This is not intended as medical advice but is purely for informational purposes.

Write Dr. Ken McMillan at Ask The Vet, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email vet@progressivefarmer.com.

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