Making sure your cattle keep their tails: Watch for ergot on pasture

Farm Forum

Almost every summer I get calls about cattle losing their tails. It seems like a strange reason to call the vet, doesn’t it? After all, cattle can function without their tails. It might be a bit more challenging to swat flies, but other than that I can’t think of too many reasons not having a tail would prove debilitating.

But why would tails fall off of cattle? First, I should better define the problem. It’s not the whole tail that falls off. Usually it involves just the tip that holds the tail switch. The lack of a switch makes it look like the cow is sporting a broom handle from the back end. Usually only a few cattle in a herd are affected.

Why would a cattle producer worry about some lost tail switches? For commercial cow-calf producers it might not be a big deal. But for those raising show calves, bulls, or heifers to sell, the loss of a tail means the loss of a sale. It has nothing to do with the reproductive worth of the animal, but to buyers it’s an undesirable defect. A high-dollar show calf transforms into a feedlot critter with the simple loss of a tail switch.

We racked our brains for an answer to this problem for a long time. These cases typically showed up in late summer, so we focused on pasture conditions. Selenium toxicity, trauma, tail mites, and ergot toxicosis were all on the list, but we could never come up with a smoking gun.

Then we had a case come through the diagnostic lab a couple summers ago that steered us toward a cause. A South Dakota producer feeding yearling bulls during the summer had 12 out of 100 lose their tail switches. The bulls were being fed a grain ration and brome hay. Analysis showed that the grain ration contained ergot.

Ergot is a mold. When it infects plants, it forms an “ergot body” in place of the seed in grasses and grains (brome grass, wheat, barley, rye, etc.) This ergot body is dark brown to black and resembles a mouse or rat dropping growing in place of the seed. Once you see it, you’ll recognize it easily thereafter. Infected grains fed to animals, as in this case, can present problems for animals being fed, while pasture grasses that have headed out can cause problems for grazing animals.

Ergot’s connection with tail loss is that it contains toxic alkaloids that constrict blood vessels in the animals’ extremities (e.g. the tail). Those tissues are starved of blood flow. A dry gangrene can result, and the withered body part falls off. In severe cases, the feet and ears can also be affected.

Cool wet springs followed by warm weather are good conditions for ergot body growth. Therefore, problems vary from year to year and among locations. On a recent trip to Pierre from Brookings, I found ergot in the roadside bromegrass in one location, but not in two others.

What to do, if anything, about ergot exposure is the immediate question for cattle producers. For commercial producers not hung up on cosmetics, it might not be worth worrying about. For show calf or purebred producers, the stakes are much higher.

As with any toxic substance, problems with ergot depend on the dose – and remember, the ergot is only present in the seeds, or heads, of the grasses. Pastures grazed such that most grass never heads out are low-risk. Ergot exposure is more likely when cattle are turned into pastures where the grass has headed out already. It’s hard to know how much ergot on pasture represents a risk, but producers raising show calves or sale animals should scout those pastures before turning those animals out. Better safe than sorry. It’s also worthwhile to check grain and hay sources too.

Unfortunately there is no vaccine or antidote for ergotism, nor is there a test in the animal to diagnose it. Awareness of the problem and avoiding contaminated feed are the only defenses we have. Also, tail problems can come from other causes too. Your local vet is the best person to help you sort out those issues.

Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University. He can be reached via email at or at 605-688-5171.