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Please pass the salt

Woody Lane for Progressive Cattle Published on 23 April 2021

Salt, minerals … minerals, salt … aren’t these the same things? Everyone, it seems, has a question about minerals, like “Why do some mixtures contain only 4 percent salt while others contain 90 percent salt?” or “Why won’t my animals eat it?”

This topic is like a Byzantine market, with all sorts of ballyhoo and potions. Well, let’s just dive in.

First, I’ll try to clear up some jargon. In the feed store and in farmer/rancher parlance, the word “salt” means sodium chloride – simple white salt. One atom of sodium combined with one atom of chlorine. NaCl – the same stuff you put into soups. Actually, the rest of the chemical industry uses the word “salt” to mean nearly any combination of positive- and negative-charged ions, such as magnesium sulfate or potassium chloride or calcium carbonate. But for agriculture, let’s stick with simple sodium chloride.

The term “minerals,” on the other hand, means a mixture of things: salt (NaCl) and other compounds containing elements such as magnesium or potassium or iron or copper, usually combined in a lick block or in a bag of loose minerals. That’s what you see when you walk into a feed store. But this farm definition would greatly displease a chemistry teacher because in chemistry the word “mineral” generally applies to many types of inorganic substances such as magnesium or rock phosphate or borax or diamonds. And in certain areas of the country, some ranchers even call white salt their “mineral,” which makes everything as clear as mud.

Here, I’ll refer to the mixture of salt plus other minerals as a “trace mineral mix” (TM mix).

Get a taste for it

One main principle underlies all strategies for mineral nutrition: Animals crave salt. That’s why livestock lick those unappetizingly concrete-like mineral blocks – because they’re trying to consume salt. Cattle don’t necessarily like pure magnesium or selenium or potassium – in fact they usually avoid those chemicals. But feed companies know animals want salt, so they add the less palatable trace minerals into a mixture with salt and call it “trace mineral salt” or a “trace mineral mix.”

How much salt should be in a TM mix? Well … I’ve seen successful mixtures that contained anywhere from 4% salt up to 90% salt. There’s nothing magical about the level – animals are very good at regulating their own intake of salt. They’ll eat what they need. If a mixture contains less salt, animals will eat more of it. Companies design their trace mineral recipes to balance the intake of trace minerals with the anticipated intake of salt. But we live in an economic world, so here is a no-nonsense bottom-line logic: Feed companies that make mineral mixes only make money when they sell bags of minerals. The more bags they sell, the more money they make. Animals will eat more mineral mix if the salt percentage is low. Therefore, how much salt should companies put into the mix? It’s their judgment call.

However, when the TM mix is used to deliver drugs or certain elements – such as selenium or Bovatec – the consumption level is critical. Variations of intake will alter the dosage. Feed companies will sometimes try to stabilize mineral intake at a relatively high level by including palatable ingredients in the mix. How many times have you heard someone say, “My cattle really liked that mineral.” Look at the feed tag – it probably lists things such as molasses or distillers grains or other flavor enhancers.

Learn some portion control

But what about the flip side? What about the times when animals don’t seem to eat enough mineral mix?

Usually this occurs because we’ve offered a second source of salt at the same time. Sometimes we do this to “add some variation,” and sometimes we do this without even realizing it – a theme with infinite permutations. I call this problem “Double Trouble.” For example, have you ever offered your animals a standard TM mix and also a bloat block at the same time? Or put white salt out next to the trace mineral mix? Or fed a commercial protein supplement or protein block that contains molasses, urea and 20-some other ingredients, including salt? Read the label. In this situation, animals will happily lick that protein block and ignore the nearby TM mix which contains selenium or a drug.

Or let’s say you buy hay for the winter, feed it and observe that your animals don’t seem to eat the mineral mix. Are you using salted hay? This is a technique that may be foreign to some folks, but salting hay is often used in the Pacific Northwest as well as other places around the country. When ranchers make hay and know the small bales are too wet to store without risk, they sometimes sprinkle white salt on the bales to draw out the moisture. Salting hay has saved a lot of barns from burning down around here, but … when that hay is fed months later, the animals also receive a nice dose of white salt along with their hay. (Don’t ever salt hay with a TM mix. Not only is the mixture more expensive than white salt, but the extra trace minerals can be toxic to animals).

Throw in some selenium

And then there is the problem of selenium. Offering a free-choice TM mixture is a good, FDA-approved method of getting selenium into animals and preventing white muscle disease. Back in the 1970s, the FDA limited selenium levels in free-choice TM mixtures to 20 parts per million (ppm) for cattle and 30 ppm for sheep, based on extensive research on experimental farms. This looked OK on paper, but it was a disaster in the field. Producers fed those TM mixtures and still saw lots of cases of white muscle disease. An entire generation of farmers concluded that feeding selenium in TM mixtures in fact didn’t work, and they returned to their tried-and-true use of selenium injections.

The real culprit turned out to be the lower-than-expected intakes of the TM mixtures, which occurred either because of large variations in intake (“The mineral ran out, and we didn’t get a chance to refill the feeder”) or the use of multiple sources of salt. Either way, if the TM mixture was the only source of selenium, the animals did not get enough of it.

In 1987, the FDA recognized this flaw and raised the selenium limits in TM mixtures to 120 ppm for cattle and 90 ppm for sheep. Reports of selenium deficiency dropped off immediately. The extra selenium provided a cushion that allowed for typical intake variations on a farm or ranch. These higher selenium limits are still in effect today.

So the next time you buy a trace mineral mix, read the feed tag … and add some spice to your day. end mark

Woody Lane, Ph.D., is a livestock nutritionist and forage specialist in Roseburg, Oregon. He operates an independent consulting business and teaches workshops across the U.S. and Canada. His book, From The Feed Trough: Essays and Insights on Livestock Nutrition in a Complex World, is available through Woody Lane.

Woody Lane, Ph.D.
  • Woody Lane, Ph.D.

  • Lane Livestock Services
  • Roseburg, Oregon