Ask the Vet

By Dr. Ken McMillan, Contributing Columnist

Question

For 37 years I've run 25 to 40 cows, mostly black Brangus. I've fed them minerals on and off, but last year I started keeping minerals out year-round. After a few months I noticed the hair along the cows' backs turning a reddish brown tint. I was told this could be a sign of copper deficiency. What does that mean, and is it something I should be concerned about?

Answer

I have seen similar occurrences on black cattle before, but because we never observed any production issues related to it, I never really explored it further.

True copper deficiency is most common in growing animals. A change in coat color is the sign of copper deficiency that most people point to because it's easy to see. But real copper deficiency can cause what I call "pocket book changes".

Copper is a critical component of hemoglobin production and a properly functioning immune system. Signs of a real deficiency often include diarrhea, generalized unthriftiness, reduced weight gain or weight loss, anemia and lameness. We have documented a few incidences of copper deficiency in our area. Many of our Southeastern soils are low in copper. In the West, an excess of molybdenum often interferes with copper uptake into plants.

When I look at minerals, my concern is more focused on who made the mineral and whether or not the cows eat it. Percentages and PPMs (parts per million) mean little in the big picture, if cows do not consistently consume the right amount of mineral.

Another issue can be the form of the minerals. Often the oxide forms are not as available as other forms. Additionally, one mineral can affect the availability of another mineral. An excess of iron or molybdenum can interfere with copper and other minerals. So in my mind, the reputation of the company manufacturing the minerals is a whole lot more important to me than what the tag on the bag says. A reputable company or supplier will always stand behind their product.

I believe every farm needs a good mineral program designed for that particular operation. Some people recommend different minerals at different times of the year and for different classes of cattle, but there needs to be a complete and balanced mineral available at all times.

Work with your veterinarian, Extension agent or farm supply store to develop a mineral program that fits your farm. Unless the mineral you were using contributed to a problem you already had, I doubt using it on an occasional basis made much of a difference.

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