Optimizing Mineral Supplementation for Beef Cattle Grazing

The ardent greens of spring are upon us! The wonder of new growth and life never ceases to overwhelm me in the Spring. As we move through this glorious season though, it is important to consider how we will manage the blessing of the forage to continue to reap its bountiful rewards.

As I considered this article, the typical warnings of the "spring flush" were my complete intent. And, truly, managing our beef cattle during the early grazing season is important. Many experienced graziers recognize, and likely have a story or two related to, the importance of magnesium supplementation this time of year. Young forages have abundant potassium. Potassium and magnesium are antagonistic to one another in the animals' body. This means we must increase the amount of magnesium we feed during the spring months to cattle. This is especially important to combat the excess amount of potassium that can reduce magnesium absorption and result in a condition known as grass tetany.

Not too long ago, Drs. Aaron Berger and Mary Drewnoski from the University of Nebraska published an article in Beef Magazine warning that tetany, while most often considered a problem in the spring, can occur in cattle fed winter stored forages as well. These authors cited that analyses of grass, alfalfa, and cereal hays fed from winter storage must be tested, with mineral analysis, in order to ensure what they dubbed "winter tetany" does not crop up in the beef herd.

When I was a young, undergraduate student at the university they taught us to feed cattle a 1:1:1 ratio of magnesium oxide : trace mineral salt : grain at least 2 weeks before cattle were put to pasture. The grain ensures that all cattle consume the supplement and the ratio allows a producer to continue to use the mineral of their choice by just blending in the additional magnesium on their own. The reality is that the solution to either grass tetany or winter tetany situations would simply be to feed a mineral with elevated magnesium, often referred to as HiMag mineral, year-round. And, fortunately, this form of prevention is fairly inexpensive and easy to come by. There is no real disadvantage to the cow herd and the insurance it provides is relatively effective.

One of the challenges that I see in our grazing systems is that we want to operate on a set-it-and-forget-it mentality with supplementation. If I purchase 4 or 5 bags of mineral, HiMag or otherwise, at the beginning of the month, I want to just set it out there and forget about it until next month. While many of the readers that have heard me speak recognize that I often use the "university answer" of It Depends! In this instance, I will state outright, with no university answer, that the set-it-and-forget-it mentality for minerals is the Wrong mentality.

Minerals are reactive compounds. We want and need them to be. That's why they are effective as coenzymes in many systems throughout the body, impacting everything from energy metabolism to nitrogen excretion to reproduction. This means, that if we simply set out our minerals once a month, they will break down and they will change. This process in the scientific community has a fancy name called oxidation. We no doubt have all discussed it more simply as weathering. But, regardless of how we discuss it, the point is that minerals that are set and forgotten, may not be as effective.

In addition to their efficacy, by law, every mineral tag lists feeding directions. If we don't pay attention to those directives we may realize challenges…perhaps not immediately, but maybe after calving when the cow does not clean out (pass the afterbirth), or at rebreeding when our breed back is not what it ought to be, or at weaning when we do not have as many pounds of calf to sell.

Well then, what should be done? My recommendation is to start by reading your mineral tag. Be honest with yourself and do the math. If the tag says to feed 4 ounces and you put out a 50-pound bag, you better be feeding 200 cows that day. If you only have 40 cows at home and the recommended feeding is 4 ounces per cow per day, then those cows only need 10 pounds of mineral each day, or a 50 lb bag every 5 days. If they consume more than expected, you can relocate the mineral feeder, for example, by increasing the distance to the waterer, to reduce intake. If they consume less than expected or required, you can move the mineral closer to the water source or mask the required mineral with a little bit of grain to encourage intake. But, don't overdo the grain; and, make sure the cows have plenty of space if you're using grain so that they can all access the supplement at one time. Generally, less than half a pound of grain is enough to encourage intake.

The distance to the water is often overlooked but critically important. Water can alter mineral intake because most mineral supplements rely on salt to regulate intake. I always use the potato chip analogy in my classes. At some point, when we're eating potato chips, we get thirsty. If we do not have access to a beverage, we likely will stop eating the potato chips. But, if we have a beverage in our other hand, we'll take a drink and keep eating potato chips….if you're not following, the minerals are the potato chips and the water source is the beverage. Adjusting the distance between the mineral feeder and the water source may help you manage the mineral intake.

The moral of the story is, as you head into this grazing season, don't just set it and forget it. Don't just think about the HiMag you need this spring and miss the opportunity to optimize supplementation for the rest of the season. You cannot manage what you do not measure. If you have never closely monitored mineral intake, the time to start is now. Better to find out if the cattle are deficient because you aren't putting out enough or if the whitetail deer are just eating all your expensive supplement!