– Neighborly Advice –
Minerals matter
A practical guide for Tennessee cattle producers
By Josh Zeltwanger, Ph.D., ProTrition Ruminant Nutritionist
Forage, protein, and energy usually get the spotlight in cattle nutrition, but minerals often determine whether the whole program works as intended. Minerals support immune function, reproduction, growth, milk production, hoof and bone strength, and overall thriftiness. In the southeast, mineral nutrition deserves special attention because pasture mineral content can shift with soil type, fertilization practices, rainfall, and stage of plant growth. Even a good-looking pasture may not consistently meet the animal’s mineral needs, especially during late gestation and early lactation. Why mineral programs pay
Mineral deficiencies and imbalances rarely announce themselves with one clear sign. More often, they show up as “background problems” — lower conception rates, weaker calf vigor, higher sickness pressure, reduced weight gains, or inconsistent performance from pasture to pasture. These issues can be expensive, and they’re difficult to correct quickly because minerals influence body systems over time.
Balance matters as much as amount. Calcium and phosphorus are tied to bone, growth, and milk production. Trace minerals like copper and zinc are closely linked to immunity and reproduction. Selenium and iodine play important roles in muscle function, thyroid activity, and calf health. Another reason mineral programs are worthwhile is that minerals can interact. For example, high levels of sulfur or iron in the diet (or water) can reduce the availability of certain trace minerals, particularly copper. Since most operations don’t routinely test every forage source and water supply, a well-designed mineral program helps reduce risk when conditions change.
Balance matters as much as amount. Calcium and phosphorus are tied to bone, growth, and milk production. Trace minerals like copper and zinc are closely linked to immunity and reproduction. Selenium and iodine play important roles in muscle function, thyroid activity, and calf health.
Complete mineral vs. trace mineral salt Many producers only utilize trace mineral salt because it’s easy to find and inexpensive. The limitation is it’s mostly salt, with added trace minerals, and it often does not provide enough of the “macro” minerals that forage-based cattle frequently need — especially calcium, phosphorus, and magnesium. It also may not include vitamins (A, D, and E) that can be limited when cattle consume stored forages or when pasture quality is inconsistent.
A complete free-choice mineral is formulated to fill common gaps in pasture and hay diets and to deliver nutrients at a predictable intake level (often listed as ounces per head per day.) Compared to simple trace mineral salt, a complete mineral typically offers:
• Broader coverage: macro minerals plus trace minerals, and often vitamins.
• More dependable delivery: it’s designed so cattle reach a target daily intake rather than just “licking salt.”
• Better fit to the season and class of cattle: products are commonly tailored for bred cows, lactating cows, or growing calves.
In practical terms, a complete mineral is more likely to support reproduction, immunity, and performance because it addresses what the forage may be missing — not just salt cravings. High-magnesium mineral is important in Tennessee High-magnesium (hi-mag) mineral is a type of complete mineral formulated with elevated magnesium to help prevent grass tetany (low-blood magnesium). Grass tetany is most often seen in lactating cows grazing lush, cool-season pasture. It can progress quickly — often with minimal warning — and may lead to muscle tremors, staggering, collapse, and death if not treated promptly.
Tennessee conditions can increase risk because spring growth of tall fescue and other cool-season grasses can be low in magnesium and often high in potassium. Those factors can reduce magnesium intake and absorption right when cows’ magnesium demand is high. Risk tends to be greatest in older cows, heavy milkers, and cows in early lactation. Cool, wet, cloudy weather and rapid pasture growth can further raise the odds.
Magnesium is not stored in the body in large, readily available reserves. That means prevention is far more effective than trying to “catch up” after problems begin. Therefore, timing is critical: hi-mag mineral needs to be in the cow before she enters the high-risk window.
• Start feeding hi-mag about 2-4 weeks before spring green-up.
• Continue through the main risk period when cows are grazing lush, rapidly growing cool-season pasture.
• Pay extra attention when cows are calving and entering peak lactation, or when grazing small grains or heavily fertilized cool-season fields.
For more information about effective mineral programs, visit with your local Co-op feed specialist.