“I dunno, I guess there’s sumthin in it they need.”

In the early 1960s, shortly after I began a vet practice in Missouri, I was called to treat a sick animal on a hill country farm NW of town.  The owner, Glenn, had called me several times in the past, so I was somewhat familiar with Glenn and his operation.  This time, as I was getting ready to leave, he said, “If you have time, I’d like to show you something interesting.” I said “Sure”, and we climbed into his 4WD pickup and drove up into the hills on the back side of his farm.  We came to a ravine or coulee several yards wide, and with almost perpendicular walls, you could easily see the different layer that made up the soil profile. Several cows were in the gully and some were licking at one of the layers. Glenn pointed out that this layer had been stripped out to the depth of a cow’s tongue. 

Glenn said that every spring, when he first turned out his herd they would all congregate in this gully and lick on one narrow layer of the clay walls. They would occasionally visit the gully during the grazing season.  The exposed layer did not look much different than the rest or the walls but 0bviously had a great appeal to the cattle.

As this was several years before I encountered the concept of self select minerals, I was at a loss to understand what I was seeing. I asked Glenn, “Why do you suppose they do that?” He answered, “I dunno, I guess there’s sumthin in it they need.”  


Looking back, that’s a pretty good explanation and still valid today when someone asks, “Why do animals eat what they do?’. All our nutritional knowledge is no match for the nutritional wisdom of our animals. 

I never did find out the ingredient the cattle were after.  It could have been a layer with a high level of an essential mineral or more probably it was a particular type of clay similar to bentonite, attapulgite or montmorillonite clay. It is not uncommon for cattle or horses to eat plain dirt (probably for its clay content) to alleviate digestive problems.  Many different types of clay have a long history of use in humans and animals. Some of the effects and benefits follow: 

  • Clays physically bind to acids and toxic substances in the stomach and digestive tract. 
  • Clays provide a source of silica, essential to all body tissues. 
  • Clays absorb heavy metals. 
  • Clays detoxify by reducing mineral imbalances.  
  • Clays bind aflatoxins, mold and fungal toxins, de-wormers, and antibiotics.
  • Clays have antidiarrheal properties and may work by adsorbing the diarrheal pathogen. 

If you do not have a source of clay on your farm, I suggest you provide some clay products for your animals.  The health benefits may surprise you.   

For a natural, nutritional clay product,

check out  “MOP”  from 

Advanced Biological Concepts -