Testing for mineral deficiency provides opportunity to supplement cattle properly

Mineral deficiencies result in poor conception rates, non-breeders, open cows at pregnancy checking, white muscle disease, poor growth, immune impacts and more.

Utah State University’s Jeffrey Hall spoke to attendees of the 2018 Cattle Industry Convention and National Cattlemen’s Beef Association trade show, explaining the impacts and importance of managing for mineral deficiencies.

Finding deficiencies

“I had one rancher tell me he doesn’t supplement his cows during the summer because they’re on green grass and don’t need it. It doesn’t work that way,” Hall said, noting he has had ranchers tell him they supplement with alfalfa or other things and don’t need to supply other mineral. “That’s not true, either.”

Hall continued hair coat is also not a good indicator of copper deficiency.

“Everybody talks about hair coat color change, but I’ve seen severely copper deficient cows that were shiny black,” Hall said. “That doesn’t work either. A hair coat abnormality may be a copper deficiency, but zinc deficiency can also cause a blanching of the hair, too. Just because they don’t have it, though, doesn’t mean they don’t have a deficiency.” 

At the same time, Hall continued, “I also see guys that have a mineral plan and poor conception rates.” 

When the cattle were tested, 100 percent showed severe copper deficiencies.

“Even though a ranch may be on a supplement plan, if we aren’t testing our cows to make sure are in an adequate state, they may not be,” he said. 

Adequate consumption

While some ranches may be supplementing their cattle with minerals, Hall said many ranchers don’t know how many pounds of supplement each cow receives. 

“Now is a great time to do that, as we’re figuring our taxes for the year,” he said. “Calculate the number of pounds purchased last year, subtract what is left in the barn and multiply it by 16 to get the total number of ounces used in a year. Divide that by 365 days and the number of cows to get how many ounces per head per day was fed for the entire year last year.”

Hall emphasized, “Over half the guys I talk to find out their cows are eating significantly less than what the label says they should be.”

“Oftentimes, it’s not that we have a bad supplement. It’s that the cows aren’t eating enough of it or it doesn’t have a high enough amount of absorbable mineral,” he said. “If we don’t test, we won’t know.”

Sampling

When sampling, the liver is the most ideal sample site. 

“For some minerals, blood testing is adequate,” Hall said, noting selenium is present and can be easily tested in the bloodstream. “For copper, blood testing does not work.”

As an example, in a group of 10 cows, liver biopsies showed 100 percent copper deficiencies, but only one of 10 had blood tests confirming low copper levels. 

“The way I interpret blood test is, if I see one in 10 has a copper problem, it’s a whole herd problem,” he said. “If I see two out of 10, this herd is significantly copper deficient.”

Blood serum is also a poor indicator of zinc deficiencies. 

When herd testing, Hall recommended testing groups of animals, rather than single animals. 

“We need to always test groups of animals,” he said. “A single animal does not give us good results.”

Hall also encouraged testing normal animals that die of causes other than health reasons. 

“If we have a cow that breaks a leg and needs to be put down or is hit by a car, take a liver sample, put it in the freezer until we get two or three and send them in for sampling to get an idea of where the herd is,” he said. 

Testing cull cows is also appropriate, if those cows go directly to slaughter. 

“Don’t test animals that have been put in a feedlot for 60 days before slaughter because they’re not going to be representative of the herd,” he said, “and don’t test animals that have been sick, were treated with everything under the sink and then died, because they’re also not going to be representative of the herd status.”

Feeding

Hall also noted, when supplementing for minerals, it is important to not cut the mineral with salt to reduce their intake. 

“I may have a product that has a four ounce per head per day intake and it probably works – if they get it 365 days a year,” he explained. “If they haven’t had any for the last four months, we have to let them rebuild their system.” 

He continued, “I have never seen a case where cows have ingested an excess of copper in a free-choice supplementation program.” 

While Hall has seen a few isolated incidents of overconsumption of copper in animals in feedlots fed high chelate concentration supplements or in dairy cattle, it is not common in range cattle. 

The chemical form of the mineral can also make an impact on the nutritional status, explaining, at identical concentrations, one form of a mineral can be absorbed more quickly and more efficiently, and it remains in the body longer. 

However, often, the form of mineral that is most easily absorbed is more expensive.

“The chemical form can make a difference on how effectively a mineral is absorbed and utilized,” Hall said.

For vitamins A and E, Hall said testing is very expensive, so supplementation is often the most cost-effective route. 

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at saige@wylr.net.