Dean Kreager, OSU Extension Educator ANR, Licking County
(Image Source: Lugtenburg et al., 2016)
In2021 we were able to live by the motto, “if it can happen, it will.” Back in August and September, I heard reports of area farms having animals diagnosed with ryegrass staggers. Not being familiar with this condition, I did some research and went out to visit one of these farms.
Just as a reminder, this was the same time that many farms in this part of the country were also battling fall army worms in hayfields and pastures. These are both uncommon occurrences in our area, but appeared at nearly the same time.
If you have never heard of ryegrass staggers, I’m not surprised. This issue is usually reported in Australia and New Zealand, but Ohio is near or at the top of cited cases within the United States. While staggers have been associated with some species of warm season grasses, the culprit here is perennial ryegrass.
This cool season grass can be a high-quality forage in Ohio, as it does well in cool moist areas.
Endophytes
When I think of endophytes, which are organisms that live in plants, I think of Kentucky-31 Tall fescue. Endophytes are not all bad and can provide benefits to their host plant, such as insect and disease tolerance. However, some endophytes have negative impacts on livestock.
Perennial ryegrass can contain an endophyte capable of causing ryegrass staggers. Neotyphodium lolii is the endophyte in perennial ryegrass that can produce compounds called tremorgens, which can have neurological effects on some animals.
These compounds are at the highest concentration near the base of the plant and in the flowering stalk. The toxicity of these tremorgens in baled hay has been shown to maintain for at least two years.
Symptoms
Ryegrass staggers is known to affect cattle, sheep, horses, llamas and alpacas. Reported cases I heard about in Ohio this year appear to be largely in alpacas. Close intensive grazing in the late summer to fall is often associated with this problem.
According to the University of Kentucky, symptoms may start with tremors in the head, neck and shoulders and progress to staggering, salivation, collapse and seizures. When removed from contaminated pastures, animals usually recover within a week or two.
Death is not common, but can happen. Often it is due to accidental injury, such as head trauma or drowning related to lack of body control. The only known effective treatment is to remove the animals from the infected area.
Prevention
Prevention of ryegrass staggers typically involves reducing the amount of toxin the animal consumes. Moving animals to pastures with less potential contamination can reduce the amount of toxin consumed. Since cases in Ohio tend to be in late summer or fall, potential problem areas could be grazed in the spring to mid-summer.
If possible, maintaining a higher grazing height will also reduce consumption of the higher toxin concentration portions of the plants. Like fescue, there are novel endophyte varieties of perennial ryegrass that have been developed and are successful at preventing ryegrass staggers.
Most of this work has taken place in Australia and New Zealand, so locating seed sources could be challenging. Terminating a pasture area and then reseeding with a novel endophyte variety or an alternative forage are also options.
With the case I visited, at first it appeared that the pastures were dominated with fescue, but upon further investigation it became apparent that the alpacas did not like fescue and would search out the tender smaller ryegrass to preferentially eat.
Even though there was a lot of fescue present, the animals were able to find enough infected ryegrass to eat. At least a few animals were affected to some extent, and one was severely affected.
While “if it can happen, it will” proved true in many locations this year, it is also true that “with experience comes wisdom,” and as we experience situations like these, we become more aware and better prepared to stop them early the next time they appear.