BOZEMAN - -Our understanding of the mineral needs of cattle is changing rapidly, but one recommendation is likely to be constant: "Know thy forage."
"Know what you have," says Ray Ansotegui, a beef cattle researcher at Montana State University. "Analyze your forage and feeds. Whatever we learn about cattle mineral needs, producers will need to know what their own resources are delivering."
The main minerals producers should pay extra attention to during the winter are phosphorus, copper, zinc, magnesium and selenium, says Ansotegui. Symptoms of deficiencies in these minerals range from reduced conception to lower disease resistance.
A common problem is zinc deficiency, because range grass is deficient in zinc by mid-winter. Deficient levels of zinc can reduce reproductive performance, disease resistance and feed intake. Feeding either alfalfa hay and grass hay doesn't necessarily help, because both hays are usually zinc deficient.
However, researchers don't yet know how quickly cattle lose minerals. If a cow's diet had enough magnesium when grazing in June, did it retain the magnesium into the fall and winter when grazing usually would not supply enough of that mineral? Such questions are part of Ansotegui's research, and he expects to begin getting answers yet this winter.
Another question that needs answering is how many Montana producers use supplements already? MSU's Animal and Range Sciences Department sent a survey this fall to producers who had received a series of departmental newsletters. Seventy-four percent of those people who responded said they would purchase a mineral supplement this winter. However, those same producers had earlier received a newsletter that described the mineral deficiencies of various forages and feeds, so they do not represent a random sample.
Over the next few months and years, other research will fine-tune much of what we know about mineral supplementation of cattle. Some of what we learn initially may be confusing, says Ansotegui, because minerals interact with each other.
For instance, you can feed what appears to be adequate amounts of copper, but if you have high levels of molybdenum in your soils, which is frequent in Montana, your cattle still could be very copper deficient. Another common situation in eastern Montana is for cattle to get high levels of sulfate and iron from the water, and that also can contribute to copper deficiency.
"That's one of the real problems with minerals," says Ansotegui. "You can go across the fence and the requirements change because of the mineral interactions. But the starting place for producers is to begin gathering information by having forage from different areas analyzed."
However, producers shouldn't have to spend a fortune getting all ranch forages analyzed.
Roger Brownson, MSU Extension beef cattle specialist suggests that producers select samples from fields that have different growing conditions. Some feed companies can analyze forages, or producers can send the samples to MSU-Bozeman's Chemistry Analytical Lab, McCall Hall, Bozeman, MT 59717.
Most analyses should be self-explanatory. If not, Brownson said producers can call him at (406) 994-3414.
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