"Dirt-osis" (Dirt toxicity in cattle)
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. Steers on a high grain diet will often chew on wood fences and lick the ground when they have rumen acidosis (grain overload). 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.
All feedstuffs contain ash. Ash is comprised of the minerals normally found in plant tissues, but also comes from soil contamination at harvest or during feeding. Excessive ash intake may lower feed intake, disrupt digestion, and may have a negative impact on health. Cattle may struggle to sort foreign objects (dirt, sand and gravel particles, or objects that cause hardware disease) from normal feed. Common sources of dirt or rocks in feed could include:
- Gravel or sand at the base of bunker silos or silo bags inadvertently mixed in the feed.
- Gravel, sand and rocks that stick to the bottom of bales during storage.
- Window mergers that roll the windrow across the ground. Mergers that physically pick up and carry the forage will accumulate less dirt.
- Mud tracked into bunkers during harvest and compaction.
- Harvesting forages with the cutter set too close to the ground.
- Rained on forages or harvesting in wet conditions.
- Mud from tires at feeding.
- High-producing dairy cows may eat bedding, including sand, because there is insufficient feed in the bunk or because they have an underlying health problem (acidosis?).
It is nearly impossible to eliminate, or remove, all dirt from the diet. Blowing dust, soil accumulated during harvest, and cattle that eat from the ground will be exposed to small amounts of dirt. Diet ash values ranging between 5 and 10% are common; however, we have observed a much wider range in the field. Dry hay, silage, and some by–product 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% 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).
- A non-responsive or “depressed” attitude.
- Decreased amounts of manure that is stiff and contains mucus.
- “Downers” that are unable to rise due to weakness, electrolyte imbalances, starvation.
- Normal or increased respiratory rate with some ‘grunting’.
|The small intestine of a dairy cow
filled with pea-sized gravel.
Click photo to enlarge.
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, such as Clostridium sp., Salmonella sp., and Listeria monocytogenes.
Published in Dairy Star September 12, 2009