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 fibre (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 five and 10 per cent 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 per cent 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.
Cows suffering from dirt-osis can have one or more of the following signs: Off feed (anorexia); non-responsive or “depressed” attitude; reduced, stiff, mucus-like manure; inability to rise due to weakness, electrolyte imbalances, starvation; normal or increased respiratory rate with some “grunting.”
There are no specific tests for dirt-osis. Measuring the major electrolytes in blood often reveal low chloride, low potassium, metabolic alkalosis and sometimes low sodium. Cattle with low blood electrolytes are usually in the later stages of disease and have a poor prognosis.
One method to screen the herd is to grab feces with a gloved hand and feel for gravel or sand. Another method would be to put feces in a palpation (AI) sleeve, add a few cups of water, mash it up, and hang the sleeve with the fingers pointing down. If the tips of the fingers accumulate sand after a few hours, there may be a problem that requires further investigation.
Efforts to prevent large amounts of dirt will prevent losses to dirt-osis. Limiting the amount of dirt in feed through proper forage harvesting, storage and feeding will also reduce the consumption of bacterial pathogens commonly detected in dirt.
For a more detailed article on this subject, visit the University of Minnesota Extension dairy website at www.extension.umn.edu/dairy and look for the article titled “Dirt-osis: dirt toxicity in cattle.”