Considerations for cattle mineral nutrition provided
Mineral metabolism plays many roles in the beef cattle body including immune function, bone and muscle growth, feed efficiency and reproductive performance. Mineral nutrition can be a complicated subject, and many producers seek opportunities to increase their knowledge on the subject.
Professor of Beef Feedlot Nutrition at Iowa State University, Dr. Stephanie Hanson, breaks down why minerals are an essential part of cattle diets, the sources of minerals and how to strategically supplement beef cattle in the July 9 Cattlemen’s Webinar Series presented by the National Cattlemen’s Beef Association (NCBA).
Macro vs. micro minerals
Hanson breaks cattle mineral requirements into macro minerals and micro or trace minerals.
Macro minerals, such as calcium, magnesium, phosphorus, potassium, sulfur and sodium make up approximately one percent of the diet, but are not stored in large, easily accessible quantities in the body. For this reason, macro minerals must be consumed in constant supply.
“We generally don’t worry about being sulfur deficient,” Hanson shares. “In fact, it’s often just the opposite. Same with potassium.”
Magnesium, phosphorus and potassium are minerals producers should keep an eye on, along with sodium, because it is important for driving mineral intake, according to Hanson.
“Luckily, most of our forages are going to be really good sources of these minerals,” says Hanson.
“Micro or trace minerals can easily become deficient and negatively affect cow performance,” Hanson notes. “Two micro minerals we think about a lot in the beef industry are copper and zinc, because our forages tend to be deficient in them.”
“However, iron is something we typically don’t need to think about supplementing because our forages are plenty high in iron and generally run two to three times higher than cow requirements,” says Hanson. “In fact, iron is an antagonist to some of the other critical trace minerals like manganese and copper.”
In contrast to macro minerals, trace minerals are more easily stored in the body.
Hanson shares, “One of the cool things the ruminant does is store these trace minerals, and they can have slightly more inconsistent intake and be able to utilize some of that storage for later.”
Forage mineral content
Mineral content of forages varies greatly, even within a geographical location and can be influenced by species, soil characteristics and fertility, plant maturity and climate conditions. Hanson recommends testing both forages and water if producers mix their own mineral supplements.
“All of these conditions will change how forages want to take up or are able to take up minerals,” notes Hanson. “The net effect of this is when a cow consumes the forages, she is getting a different mineral composition in each mouthful.”
“Some minerals such as phosphorus can be affected by forage maturity,” she shares. “The phosphorus in producers’ pastures is likely decreasing right now as forage matures.”
“Trace mineral content of forages can vary considerably,” Hanson adds. “Very consistently across the U.S., survey data would suggest our forages are moderately to severely deficient in copper and zinc.”
“In general, calcium in a pasture is often sufficient for gestating and lactating cow performance, but phosphorus can be very variable,” says Hanson. “Producers need to consider calcium and phosphorus together because the metabolism of one effects the metabolism of the other.”
The recommended calcium to phosphorus ratio is no less than 1:1.
Hanson also stresses the concentration of a mineral in the diet does not always guarantee adequate status in the body. An example is grass tetany, where a magnesium deficiency is created because high potassium and nitrogen interferes with magnesium absorption in the rumen.
When asked when producers might be running into a mineral deficiency, Hanson shares, “If producers notice poor pregnancy rates unrelated to a heat stress event or artificial insemination error or unexplainable weight loss, most likely they have a mineral deficiency of some type.”
Hanson explains poor pregnancy rates could be a deficiency in copper, magnesium or zinc, while weak newborn calves could be deficient in selenium or iodine, as well as vitamins A and E. Placenta retention can also be attributed to selenium deficiency.
Hanson also shares if feedstuffs or soils are known to be deficient in a mineral, cattle will be deficient unless supplemented.
In terms of self-regulating nutrition, Hanson believes cattle cannot make their intake choices based on mineral requirements.
“Palatability, not a demand for cobalt or zinc, is the factor driving mineral intake,” she explains. “For most free choice minerals, salt will be the intake driver.”
Hanson also notes producers have the ability to manipulate mineral intake to a degree.
“There is evidence animals will select a diet that tastes really good, but is not good for them, even to the point of death,” says Hanson.
Minerals added to complete a total mixed ration (TMR) are an easy way to assure the best mineral intake to meet the needs of animals, according to Hanson. While not an option for every operation, a TMR is usually the best strategy utilized by feedlots.
Backgrounding operations heavily rely on minerals added to a corn or distillers’ grain supplement and often ignores forage mineral value. Minerals are provided in self-feeding situations in free-choice supplementation.
“The biggest challenge with free-choice mineral is intake varies considerably. The boss cow is there all the time, while less dominant cows will have a hard time getting into the feeder,” Hanson notes.
“No mineral is an island,” Hanson explains. “We can’t ever try to fix the problem with just one mineral supplement. Take a holistic approach when coming in with a supplement program.”
Averi Hales is the editor for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.