Copper Sulfate and Ergot

The following letter from a reader was run in the June 8th Issue of The Blood-Horse, a sister publication to The Horse: Your Guide to Equine Health Care. The subsequent response is from Dr Jimmy C. Henning, Extension Professor of Agronomy at the University of Kentucky, and gives some insight on ergot.

Ergot Warning

I am writing this letter as a warning to anybody who has broodmares or cattle.
For the past three breeding seasons (1999, 2000, and 2001) I have lost one-third of my crop of foals mostly from late-season unexplained abortions. Many people said it was fescue, which we have always had with no problems, or the abundance of Canadian geese, which we also have had since the 1970s with no problems other than the mess.

My local veterinarian and the veterinarians in Kentucky went over all the records of the mares and had no suggestions other than "put the mares on antibiotics," which I was ready to do, even though I do not believe in using them unless necessary.

Then last spring, our feed man, whom we had contacted to see if there had been any change in the ingredients in our formula, called to say he thought he had discovered the cause of our problems. He told us that a farm near us had cattle whose feet had fallen off from a fungus called "ergot." When he researched ergot on the Internet, he discovered the symptoms in horses were exactly like ours. Apparently, ergot has always been known in the north, but it is now moving south, having been documented as far south as Alabama. It is prevented by fertilizing with copper sulfate, which we did and no mares have aborted this year.

From what I know about ergot, it can grow in any kind of grass, although it's more prevalent in fescue. It can also be in the hay, which we now test before buying. The symptoms are not quite the same as with mare reproductive loss syndrome, but the results are the same, though for me, more devastating as it happened for three years in a row before we knew what it was.

I urge everyone to have their fields checked and make sure he copper levels are high enough so that this lethal fungus cannot grow

Peggy Augustus
Keswick, Va.

Response from Dr. Jimmy C. Henning, Extension Professor of Agronomy at the
University of Kentucky:

In a recent letter to the editor of The Blood-Horse, a Virginia horse owner indicated that applying copper sulfate to their pastures seemed to alleviate an abortion problem, and strongly advocated that horse farm managers check their pastures/soils for copper. They recommended to 'make sure that the copper levels are high enough so this lethal fungus cannot grow.' The letter also implied that fertilization with copper sulfate will prevent problems arising from the ergot fungus.
UK does not recommend that horse farm managers apply copper sulfate in an attempt to minimize MRLS or the ergot fungus in pastures.
'Ergot' refers to a type of fungus and its chemical products, alkaloids, that are known to cause problems in horses. Ergot toxicity arises from fungal growth in the mature seedheads of grasses, and the ergot appears as visible black growths. This fungal growth appears later in the season (usually June), only in grasses with mature seedheads and then only under moist conditions. Mowing pastures to minimize seedheads should take care of this problem. Applications of copper sulfate as fertilizer will not prevent the growth of the ergot fungi in the seedheads of grasses.
Tall fescue infected with the endophyte can also produce ergot- type alkaloids, but these are always internal to the plant and are not eliminated by mowing pastures. These compounds have been measured in pastures as part of the UK MRLS Monitoring program since late February. These are either low are at seasonally expected levels. Some fields have had elevated levels of ergot alkaloids originating from tall fescue, but this pasture trait has not been correlated to MRLS.
Copper levels in many Kentucky forages can be low. Diets are commonly supplemented accordingly. Applying copper in fertilizer is not recommended because it will be tightly bound in the soil and therefore will not effectively increase copper in the diet of grazing animals. Applying large amounts can also be toxic, especially to sheep. In addition, horses that had early or late abortions in 2002 consistent with MRLS had normal copper levels in blood.
Making sure that copper requirements are met in the overall diet of horses is prudent. However, there is no real need to test soils for copper, and certainly no evidence that fertilizing with copper sulfate will minimize the occurrence of the ergot fungus or MRLS.
Dr. Jimmy C. Henning
Extension Professor of Agronomy
University of Kentucky
N222D Ag Science North
Lexington, Ky 40546-0091
859 257 3144

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More

Free Newsletters

Sign up for the latest in:

From our partners