Yes, your cow herd probably has a mineral deficiency. Yes, even if you have a supplementation program.
That was the general message of Dr. Jeff Hall, professor of veterinary sciences and toxicology at Utah State University. He spoke at the Cattlemen’s College held during the National Cattlemen’s Beef Association annual conference on Jan. 31.
Mineral deficiency can be economically damaging to a commercial operation. Mineral-deficient cows often come up open and produce weak, unthrifty calves predisposed to illness because they lack the nutritional tools they need to thrive.
“It is a very common problem,” Hall said.
Copper deficiencies are the most common and widespread in the U.S. according to Hall.
“In some areas, we’ll see copper deficiency in 70 percent of the animals we test,” he said, adding that the best situation he’s seen was one state where only half of the animals tested were deficient.
Copper-deficient cattle tend to be unthrifty, poor-gaining animals with lighter-than-usual coats, and swollen, painful joints. Severely affected calves can have rear leg weakness or even paralysis. Affected females have difficulty getting pregnant.
Selenium deficiency is also widespread but is not as uniformly high as copper deficiencies. Hall said he had seen ranges of selenium toxicity in rare cases to up to 70 percent of a state’s tested animals being deficient.
Symptoms of selenium deficiencies include weakness, muscle tremors, lack of coordination, and general unthriftiness. In calves, “white muscle” disease occurs and heart and breathing issues can result. Hall said that white muscle disease can be observed in the calf’s tongue well before they show heart problems.
Other deficiencies Hall mentioned were zinc, vitamins A and E, and manganese, but these tend to be less common.
Hall told his audience that he often gets asked why the industry is seeing such widespread mineral deficiencies in recent years. The answer—we’re looking more and better able to measure things.
“It’s always been there,” he said, but also pointed out that we are asking more of our cows than we did in the past.
“Forty-five years ago, a cow was producing two calves every three years,” he gave as an example. “That means a cow was given a year off every couple years to build her system back up. How often do we let a cow do that today?”
Causes of deficiency
The most common cause of mineral deficiency is lack of mineral content in a cow’s feed and no or insufficient supplementation.
Even where the soil contains sufficient micronutrients, the grasses cattle graze don’t take up the minerals in the amounts cattle need. Similarly, just because the hay is good—possibly because it has a lot of protein—does not mean it has the necessary nutrients.
“I had one rancher tell me, ‘I do not supplement my cattle in the summer when they are on lush, green grass because they don’t need it.’ Bull! It doesn’t work that way,” Hall countered.
There are also environmental effects that can come into play with mineral deficiency. For example, Hall noted that the incidence of zinc deficiencies increases during and a few years after drought.
Hall added that cattle producers brought some of this on themselves through their management systems.
“We’ve altered nature,” he said, asking the audience when wild ruminants give birth.
“As a general rule, a wild ruminant will typically have their babies 30-60 days after spring green up. When are we asking our spring-calving cows to have their babies today? Thirty to 60 days before anything has a chance to turn green; from a physiological and nutritional point of view, the worst possible time to be dropping a baby.”
Another major cause of mineral deficiency is a lack of available minerals. Several chemicals, such as sulfur, can bind with available minerals and render them inaccessible to the animal’s digestive system.
In this case, the form of the mineral matters. Chelated minerals are more available on a chemical level than non-chelated minerals, for example. Chelated minerals are protected and can pass through the rumen and get absorbed in the small intestine where it is most effective.
Cows and calves
Mineral deficiencies are most obvious in young calves. However, the condition of a calf gives an indication of the state of its dam.
“Calves have to be born with higher body reserves than an adult animal,” Hall explained, pointing out that milk does not contain selenium and copper. This means a nursing calf is born with all the copper and selenium it will have until it starts grazing.
“The only way a calf is born without enough body reserves—a cow will deplete her own system trying to make sure that calf has enough—is that mama ran out.”
Hall said the last trimester of a cow’s pregnancy, and especially the last 30 days, are when most of this mineral transfer between dam and fetus occurs.
“The last 30 days are critical from mama’s standpoint because her immune system has to be highly functional in order to produce adequate antibodies into that colostrum.”
Measure, measure, measure
Hall echoed what effectively was the theme of the Cattlemen’s College; you can’t manage what you don’t measure.
“Even though you may be on a supplement plan, if you’re not testing to make sure your cows are in an adequate state they may not be. I find that very common.”
He challenged his audience, asking if they knew how much supplement their cows are eating.
When it comes to testing however, Hall pointed out that blood tests are not widely reliable for all minerals, copper in particular. Instead, he advocated liver biopsies. He acknowledged that they are expensive, but they are not as invasive as one might think.
Regardless, he repeated the point about mineral deficiencies: “If you don’t test, you’re not going to know.” — Kerry Halladay, WLJ editor
