Frequently Asked Questions

CORRELATION OF ENDOPHYTE TOXINS (ERGOVALINE AND LOLITREM B) WITH CLINICAL DISEASE:
FESCUE FOOT AND PERENNIAL RYEGRASS STAGGERS

Dr. A. Morrie Craig and Dr. Linda L. Blythe
College of Veterinary Medicine
Oregon State University

Fescue foot, summer syndrome, and ryegrass staggers are all diseases of livestock related to endophyte toxins in pasture grasses. Range finding experiments and case studies of fescue foot and perennial ryegrass staggers (PRGS) were conducted on cattle and sheep under grazing and barn conditions. The main objective was to determine threshold levels of the endophyte toxins, ergovaline and lolitrem B, associated with the diseases of fescue foot and ryegrass staggers, respectively.

Clinical disease of fescue foot was produced with 825 ppb dietary ergovaline in a period of 42 days in cattle but not in sheep. Field and barn studies of natural fescue foot in a herd of sheep were conducted and clinical disease was not seen at 1215 ppb.

Lolitrem B toxin at 2135 ppb in perennial ryegrass was associated with clinical cases of ryegrass staggers in 42 of 237 sheep (18% residue rate) in the Willamette Valley of western Oregon. These were the first range finding experiments undertaken in this locale to document threshold levels of endophyte toxins associated with fescue foot and PRGS.

CONCLUSIONS: THRESHOLD LEVELS FOR FESCUE TOXICOSIS AND PERENNIAL RYEGRASS STAGGERS

With the scientific knowledge available as 2014, toxicosis is induced in livestock as follows

	Ergovaline	Lolitrem B
Horses	300-500 ppb*	Not determined
Cattle	400-750 ppb	1800-2000 ppb
Sheep	500-800 ppb	1800-2000 ppb

* should = 0 ppb for brood mares.
Related Content: Japanese Wagyu Recommended Feeding Regimen

SAMPLING STRAW AND OTHER FEED MATERIAL FOR ENDOPHYTE TOXIN ANALYSIS

Concern about endophyte-infected feed/forage materials has generated repeated questions about submitting samples for "endophyte testing." Feed/forage samples are analyzed for toxin content, not for endophyte presence. These chemical analyses are only as good as the sample provided. In other words, a toxin test will accurately represent a lot of straw or feed/forage material only if the sample is truly representative. The following guidelines will ensure that the sample(s) submitted are as representative as possible:

• Sample weight: A minimum weight of 50 grams is needed for adequate testing of replicates in the assays we perform. Feed/forage samples have widely varying density, so if you are unable to ensure at least a 50 gram sample with a kitchen scale, we suggest (at a minimum) fully stuffing a sandwich-sized plastic bag with the dried material.
• Sample consistency: Once you have obtained your sample using one of the sampling methods below, it is recommended that you air dry your sample out of direct sunlight before shipping. If your sample is not dry, it is not acceptable for testing and should not be submitted.
• Random sampling: Bales within a lot of straw, subsamples from an entire pasture, handfuls from a lot of pellets or other methods of defining a given collection of feed/forage material should be sampled at random. Random means that you have no precise reason for selecting or rejecting a specific portion of the feed/forage material to sample. Here are two ways to guard against biasing: 1) sample every fourth or fifth bale going around the stack (or truck) or driving down the row in the field/pasture, or 2) take a least 5 random samples from each of the four sides of the stack/batch of pellets.
  • A lot of straw should represent straw from one variety, harvested from the same field. If two lots of straw are in a stack, sample them separately. A truck load of straw may be considered a lot if there is no information to the contrary.

• Sampling methods and techniques:
  • Core sampler: Commercial forage samplers are available through farm supply sources. You can attach a core sampler to a brace or 2-inch drill for easy sampling. Your county Extension agent can help you locate a supplier. Ideally, the sampler should have an exterior diameter of ½ inch and a sample length of at least 12 inches. Minor deviations from these measurements are acceptable. Sample a bale by centering the core sampler in the end of the bale and drilling horizontally. Take at least 20 cores (1 per bale) for each lot of straw or other feed material. 
  • Pasture sampling: To take a pasture sample, randomly select 20 separate sites within the pasture. At each site clip a handful of grass just above the ground. If your animal typically pulls the plant up by the roots and eats the entire plant, you may wish to pull up a handful of plants at each site. Otherwise, clipping plants at ground level will be sufficient.
  • Pellet sampling: Obtain 20 random samples (handfuls) from the batch of pellet material to be tested.

Place the entire sample in a polyethylene freezer bag. Commercial clients should use the commercial client website to submit their samples, placing the automatically generated sample submission form into the bag and sealing it tightly. Non-commercial clients should follow this link to fill out an electronic form then follow the instructions for shipping detailed therein.

Please contact the laboratory at (541) 737-2872 if you have any questions!

What to consider when deciding which test or tests to request

When possible, try to determine the type/species of plant material you have. Is the feed material a type of fescue, ryegrass, a mix of both or something else?

• If you have fescue, an ergovaline test is recommended. Lolitrem B is not typically produced by the endophyte fungus found in fescue.
• If you have ryegrass, both ergovaline and lolitrem B can be present. If you would like to have only one test performed, a test for lolitrem B is recommended. The endophyte fungus that may be present in ryegrass is different than the one that may be in fescue, and tends to mainly produce lolitrem B. However, you need to be aware that ergovaline is usually produced in smaller amounts which may be a cause for concern in feed. Therefore, a test for ergovaline may additionally be requested for ryegrass.
• If you have both types of grass, tests for both ergovaline and lolitrem B are recommended.
• If you don't know the type/species of plant material in your feed, but reproduction and/or vasoconstriction issues are of concern, a test for ergovaline is recommended. If staggering is of concern, a lolitrem B test is recommended.

If you would like assistance deciding what test(s) are appropriate, or if you believe you may have an ergot problem, please call the Endophyte Service Laboratory at 541-737-2872 for consultation.