By Karl Wolfshohl
Want healthier livestock? Look at their diet. If you are supplementing it with a trace mineral mix that isn't tuned to local pastures, you could be robbing your livestock of some of their health and reproduction potential.
"When it comes to minerals, one size does not fit all," notes Warren Gill, a Tennessee specialist who has studied minerals in pastures along with Clyde Lane, a Tennessee animal scientist.
How do they differ? Let us count the ways, or at least a few.
Selenium is often deficient in Tennessee forages. On the other hand, in parts of the Dakotas and California, where soils are more basic (having a higher pH) there may be so much selenium that it actually is toxic to cattle.
Sandy soils in south Georgia and Florida tend to need extra sulfur and potassium. Elsewhere you'll sicken cattle by adding sulfur because there is so much in the soil already. In fact, too much sulfur in the forage in some places ties up selenium and copper, putting these in short supply for livestock. Excess sulfur is often a problem in pastures located down wind from coal-fired power plants.
"It's almost always an interaction between one mineral and another that causes the problem," Gill says. "Sulfur is the big bully here, beating up copper and selenium."
Potassium is another bully in some places. It may raise its ugly head in early spring, tying up magnesium, so cattle may get what's called "grass tetany" on early spring forages. That's a life-threatening malady.
How do you get too much potassium? One way is by fertilizing pastures with the old standard triple 19 fertilizer, without taking a soil test first and adding specifically what a pasture really needs.
Is this truly a problem? Absolutely. Gill says one-third of the samples they test for potassium in the spring are above 3%, which is considered the maximum tolerable level.
"If there's a bit of advice, it's to work with the companies to see how they've manufactured minerals to fit your area," Gill says. "Good ones will adapt their mix locally. I don't believe I'd use a company that has a one-size-fits-all product. Also, check your state land grant university's animal science Web site for what they recommend."
And here's one of Gill's big pet peeves: Using trace mineral salt—an old standard nearly everywhere—without some local adaptation. "It's inexpensive but it's pretty much just a colored salt," Gill says. "It does not have enough calcium, phosphorus, copper, or selenium for Tennessee, for instance. The color comes from iron oxide. Healthy cattle rarely have an iron deficiency, and you should normally avoid high-iron products."
Functions of minerals