The problem with trace mineral blocks is not what’s in them; it’s getting what’s in them into the cow.
Dr. Shane Gadberry, University of Arkansas livestock nutrition specialist, said the trace mineralized salt block does not do a very good job of taking care of mineral deficiencies, based on their lab’s analysis of forage mineral composition.
“The majority of the content of that block is going to be salt,” he explained. “Those blocks tend to contain a very low concentration of trace minerals. And the other thing that we’ll often find on the tag is that they’re using forms of trace minerals that aren’t very available biologically to the animal.”
For example, Gadberry said if the product uses copper oxide derivatives, the availability of the copper in it is only around 4 percent; with the cow only taking up an ounce from the block per day, that doesn’t account for much copper intake.
With loose mineral, the problem may be overconsumption.
“Very good minerals aren’t cheap, so we may choose to put out a week’s worth of loose mineral at a time,” Gadberry said.
The solution can be to put out a white salt block, so the animal can satisfy its craving for salt when the limited mineral supply is gone. Salt should also be made available free-choice with molasses-based supplements, which typically don’t contain that mineral. Gadberry said producers need to read the label on the molasses products. Loose mineral, he said, is the best way to address deficiencies.
“With the loose mineral, we’re generally going to have a greater intake throughout the year than what we would have with the mineral block,” he said. “The complete loose mineral will generally have major minerals at a higher level than what we want with the mineral block. Generally we’re not going to find that block fortified with any decent level of magnesium or phosphorus, so that mineral block is not going to help us with grass tetany situations.”
Trace mineral deficiencies can also be rectified with the new formulations of molasses licks, but Gadberry said that is the most expensive alternative.
“The real problem with blocks is getting them to consume enough to be truly beneficial to the animal,” Andy McCorkill, regional livestock specialist with University of Missouri Extension, told Ozarks Farm & Neighbor. “There are some types of mineral blocks and tubs that are better than the old fashioned, red trace mineral salt blocks, but generally speaking a loose mineral is the better option.” He said several companies produce softer, more palatable mineral blocks and tubs that can do a better job of achieving the consumption levels needed to meet the animal’s requirements.
It’s important that cattle get adequate amounts of calcium, phosphorus, copper, zinc, manganese and selenium year round. McCorkill said when cattle are grazing standing pasture for most of their feed, the vast majority of their mineral needs are generally met by the grass they are eating.
Research done at the MU Forage Systems Research Station at Linneus, Mo., showed that a 50-50 mix of loose trace mineral salt and calcium phosphate will meet the needs of the cow herd for most of the year.
“Through grass tetany season, the addition of magnesium oxide at the rate of one-fourth the mix should be included,” McCorkill said. “Magnesium oxide has a chalky, metallic taste that tends to deter cattle from consuming it, so to get over that it may be necessary to add some corn and dried molasses to the mix to sweeten it up a bit.”


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