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.
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SAMPLING TALL FESCUE AND PERENNIAL RYEGRASS FOR ENDOPHYTE TOXIN ANALYSIS

Concern about endophyte-infected tall fescue and perennial ryegrass seed straw has generated repeated questions about submitting samples of straw for "endophyte testing." Straw samples are analyzed for toxin content, not for endophyte presence. These chemical analyses are only as good as the straw sample provided. In others words, a toxin test will accurately represent a lot of straw only if the sample is truly representative. The following guidelines will ensure that the samples are as representative as possible.

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.

Use a 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. A minimum weight of 50 grams is needed for adequate testing of replicates in the assays we perform.

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.

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.

Bales within a lot of straw should be sampled at random. Random means that you have no precise reason for selecting or rejecting a specific bale to sample.

Here are two ways to guard against biasing: 1) sample every forth or fifth bale going around the stack (or truck) or driving down the row in the field, or 2) take a least 5 random samples from each of the four sides of the stack.

Place the entire sample in a polyethylene freezer bag and seal it tightly. Be sure to label the sample with your name, phone number, sample identification, and assay you want performed either on the bag with a permanent marker or on a piece of paper (a business card is ideal) enclosed with the sample. Commercial clients should use the website to generate appropriate labels for their samples.

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. Other wise, clipping plants at ground level will be sufficient.

Proper samples should be submitted to the following address:

Oregon State University
Endophyte Service Laboratory
Oak Creek Building, Room 139

3015 SW Western Blvd.
Corvallis, OR 97331

The laboratory phone number is (541)737-2872 if you have any questions.

Personal communication from Shigeru Miyazaki, Ph.D. May 2008
Team Leader, Safety Research Team
National Institute of Animal Health, NARO Tsukuba, Ibaraki 305-0856, Japan

Animal weight (kg) @ 1000 ppb Lolitrem B @ 1500 ppb Lolitrem B @ 2000 ppb Lolitrem B
100 1.2 kg/day 0.8 kg/day 0.6 kg/day
150 1.5 kg/day 1.2 kg/day 0.9 kg/day
200 1.8 kg/day 1.6 kg/day 1.2 kg/day
250 2.1 kg/day 2.0 kg/day 1.5 kg/day
300 2.4 kg/day 2.2 kg/day 1.8 kg/day
350 2.8 kg/day 2.7 kg/day 2.1 kg/day
400 3.2 kg/day 3.0 kg/day 2.4 kg/day
450 3.6 kg/day 3.3 kg/day 2.7 kg/day
500 4.0 kg/day 3.6 kg/day 3.0 kg/day
550 4.4 kg/day 3.9 kg/day 3.3 kg/day
600 4.8 kg/day 4.2 kg/day 3.6 kg/day
650 5.2 kg/day 4.5 kg/day 3.9 kg/day
700 5.6 kg/day 4.8 kg/day 4.2 kg/day

Based on 12 micrograms / kg body weight threshold recommended for Wagyu.

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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.