It has recently come to my attention that we have had two cases in surrounding counties of livestock death. Both cases were due to a toxic plant in pastures or a toxic insect in hay. Please make sure you are aware of potential problems in your livestock feed!
Cattle in a nearby county were killed after eating significant amounts of perilla mint. This plant is toxic to all livestock species and might be selectively grazed by your animals. It can be particularly problematic in late summer and early fall, when it has developed seeds. Perilla mint is a warm-season annual broadleaf plant, with square stems and a distinct smell. The green, heart-shaped leaves have a hint of purple on the underside. It is often found in shady areas and cattle (or any livestock) exhibit respiratory issues. Signs will present themselves within 24 hours of significant consumption and loud, open-mouthed breathing is a common symptom. The symptoms are similar to pneumonia so it important to have a clear diagnosis from your veterinarian. In terms of removal, if only in a small area, it may be acceptable to pull weeds from the ground and discard them. Herbicides may be useful, check the label to be sure it is labeled for this toxic weed. Scout the areas in late spring or early summer to eradicate from your pastures.
A local horsewoman called me a few weeks ago with a concern about blister beetles. She had heard about a load of alfalfa hay from out west that had been brought to NC, sold to local owners, and is linked to the death of 6 horses. The blister beetles can be very toxic to horses, especially if they are found dried and dead in hay. The beetle harbors a toxin called cantharidin which is released when the beetles are crushed in the hay making process. As little as 5-10 beetles can be fatal to a horse; symptoms include colic, diarrhea, kidney damage, blisters on the mouth, and several more. If your horse is exhibiting any of these symptoms, it is important to contact your veterinarian as soon as possible. These beetles feed on alfalfa so if this is a common forage source for your horse, make sure you buy it from a clean, reputable source. Midsummer alfalfa is more likely to contain blister beetles than first-cutting or late cuttings because the adults are only active during the summer months. Dividing your alfalfa hay into “flakes” and inspecting before feeding can help reduce the risk of your horse ingesting blister beetles. Discard any hay that contains beetles, simply removing them from the hay does not make it safe for consumption!
As fall is approaching, I have one more word of caution: frost damaged forages can be toxic to livestock. Pay particular attention to sorghum, sudangrass, and johnsongrass. Removing your livestock for a few days after a frost can help prevent prussic acid poisoning associated with these forage types.
This article is not meant to scare you but simply to make you aware of potential problems. Please call the extension office at (919) 731-1525 if you have any specific questions or concerns.