The wet weather we have been dealing with for most of this year has brought with it several challenges for livestock producers throughout southwest Missouri. Wet and cold weather led to increased calf losses early this year, and wet fields have not allowed farmers to harvest hay crops that appear plentiful to the average person driving down the road. But I have observed another problem this year affecting horses and cattle. While I don’t have scientific proof or hard statistics to prove my theory, it is my opinion that I have had a number of cases where the problem seemed to stem from access to tall fescue, and I am concerned that fescue toxicosis could be a significant problem this year.
Tall fescue is probably the most prominent grass in our area. Fescue is also the home to a symbiotic fungus called Neotyphodium coenophialum. This fungus appears to enhance the disease resistance and productivity of tall fescue, but it also has properties that make it in certain instances, highly toxic to cattle and horses.
In addition to the foot problems caused by decreased blood flow to the hoof and surrounding tissue, weight loss and poor thrift are common findings with consumption of endophyte infected fescue. Reproductive problems are also significant. In horses, agalactia in mares, laminitis, and foaling problems are common occurrences.
With my cattle patients this spring, the most common finding I have noticed is actual cases of fescue foot. This appears as a swollen foot that is very painful, and often will develop deep cracks in the skin and underlying tissue due to loss of blood to the extremities. This is caused by the alkaloids produced by the fungus in fescue. While it is not uncommon to find these cases every summer on pastures that are considered to be “hot," I do not normally see multiple cases in April and May. I have also noted many animals that are not shedding winter hair coats quickly and showing symptoms of heat stress even before summer has really begun.
What really caused me to consider the severity of fescue toxicosis this year is the number of cases of laminitis in horses I treated this spring. I would estimate that I have examined and treated as many cases of “grass founder” this year during April and May as I have seen in the past several years. All the animals I have suspected suffering from grass founder had been turned out on lush pastures and became quite lame within a matter of days. Basic treatment for laminitis combined with removal of the affected animals from pasture has resolved most of my cases. I have also treated multiple cases of equine dystocia involving extremely large foals. This is a phenomenon seen with fescue toxicosis in mares.
So why so many problems with fescue this year? I believe the amount of rain is having a direct effect by allowing the grass to produce large seed heads (the most toxic part of the plant). With lush conditions, most livestock owners are supplementing with hay less than in past years when pastures have been quite short. Furthermore, high grain prices are probably leading to decreased supplementation of cattle on pasture. Curing the problem probably involves supplementing feedstuffs other than fescue, considering sowing legumes into fescue stands to dilute intake of fescue and decrease the effects of the fungus, and cutting pastures short and removing cattle for the summer.
Mike Bloss, DVM, owns Countryside Animal Clinic with his wife, Kirstin Bloss, DVM, in Aurora, Mo.