Minerals can play a vital role in ensuring a cow is healthy throughout her lifetime and while raising calves, but knowing if your cow herd has the proper minerals and when to supplement can be more of a challenge. Mary Drewnoski, beef systems specialist at the University of Nebraska, says testing for macro and trace minerals in feedstuffs is a start to knowing where extra supplementation is needed.

“Copper and zinc are the most commonly deficient minerals, but others like sulfur and potassium are very important as well,” Drewnoski says. Macro-minerals needed in cattle include calcium, magnesium, phosphorus and sodium. Trace minerals needed include cobalt, copper, iodine, manganese, selenium and zinc. The body has requirements, and some of these can be stored in the body and don’t require constant intake.

Health challenges

Drewnoski says a lack of certain minerals can lead to health problems. This is seen with grass tetany in early spring, when a lack of magnesium or low amounts of calcium can lead to milk fever, especially in fresh-calved cows. Deficiencies in one mineral can also cause problems with others, causing a secondary deficiency. Sulfur can cause a deficiency in copper and lead to the need to feed more copper.

“We usually will see proper minerals in feedstuffs, but that is also why it’s important to test hay and silage for these,” she says. “Even the trace minerals should be high enough in forages, but we need to know they are.”

The goal of supplementation is to prevent subclinical deficiencies, especially those for which symptoms are not easily observed. When trying to ensure against a deficiency, a mineral shot could help — but it’s not the only answer. It’s important to know how long these injectable sources last and how much is needed when.

Mineral supplementation is also important for calf performance. A cow’s milk provides macro-minerals but is deficient in the micro-minerals. Calves rely on their livers to store the needed micro-minerals during early life. Maternal immunity decreases with time, so it’s important for the cow to have the needed minerals when the calf is in utero.

The cow’s needs changes throughout the cycle, and grass also has different mineral numbers through the grazing season. Mineral availability will vary within geographical location also, as well as by plant species, soil characteristics, soil fertility, stage of plant maturity and climatic conditions.

Mineral sources

“Testing your own forages to develop a supplementation program can be very cost-effective,” Drewnoski says. “Cattle do not have the capability to balance their own diets. They will eat what is palatable, which is salt.” Mammals, in general, will select a palatable but poor-quality diet in preference to unpalatable, nutritious diets. Palatability and not metabolic demand is the factor controlling mineral consumption by beef cattle, which is why in most free-choice minerals, salt is the intake driver. She says mixing loose salt with loose mineral can help with consumption.

Salt can be used as a tool to help with intake. Other ingredients that can be added to the mix to improve intake include molasses or distillers grains; however, those are not as economical. These can especially be needed when feeding a high-magnesium mineral mix due to the bitterness of magnesium oxide. She does caution about having too much salt available, as once cattle meet salt intake, they consume less of the mineral mix. These needs can also change throughout the year.

Through a free-choice mineral offer, important factors include weatherization of the mineral, number and location of mineral feeders and the frequency of refilling feeders. “If a mineral mix is supposed to withstand weather because the feeder does not protect the mineral from wind and rain, addition of salt can reduce effectiveness of the weatherization feature,” Drewnoski says. “An option instead of adding salt is to move the location of feeders. Try placing them closer to water or loafing areas to increase intake and further away if needing to reduce mineral intake. A good rule of thumb is one feeder per 30 cows.”

To avoid overconsumption of mineral when the feeder runs out, she suggests offering straight salt out for a day or two before offering the mineral mix again. This will help cows to meet salt cravings first. When the mineral mix is reintroduced, straight salt should be removed.

In general, knowing what minerals are available in feedstuffs through testing will help decipher what supplementation is needed to avoid deficiencies.