Beware of dirt toxicity in cattle

By Noah Litherland, University of Minnesota Extension, and Jeremy Schefers, University of Minnesota Veterinary Diagnostics Lab

Cows are not birds. They do not have gizzards and they do not need to eat dirt (gravel, sand, or soil) to physically digest the feed offered them. Yet, cattle eat dirt. Why? What happens when they do, and how much is too much?

Cattle that actively seek out and eat dirt are likely missing something important in their diet. In some cases, the missing ingredient may be effective fiber (long-stem hay) and these cattle will explore their environment to try and provide some relief. In other situations, cattle will eat dirt when they are deficient in minerals (salt, potassium, calcium, etc). Cattle that actively eat dirt or sand are likely foraging for sources of minerals to meet their nutrient requirements.

It is nearly impossible to eliminate, or remove, all dirt from the diet. With blowing dust and soil accumulated during harvest, cattle that eat from the ground will be exposed to small amounts of dirt. Diet ash values ranging between 5 and 10 percent are common; however, we have observed a much wider range in the field. Dry hay, silage, and some byproduct feeds tend to be the main contributors of ash to dairy cow diets.

Cattle that consume large amounts of dirt or rocks and have clinical “dirt-osis” may have blocked abomasums that are unable to move feed to the small intestines. The onset is usually slow and progressive over several days, perhaps a week, and up to 10 percent of the cattle in a group can be affected. Cattle may develop electrolyte imbalances because important electrolytes (chlorine and potassium) pool in the abomasum and cannot be pulled back into circulation by the small intestine. Ultimately, the cattle will perform poorly and lose weight.