Endophytic fungi (A. coenophialum and A. lolii) which infect grasses produce
ergot alkaloids that serve as the grasses' chemical defenses and enhance the vigor of
the grass. Turf-type tall fescue with high endophyte levels has been deliberately
developed to produce a greener, more vigorous, pest-resistant turf. Consumption of
endophyte-infected grass causes various toxicity symptoms in livestock.
Cattle in the southeastern and midwestern United States, where tall fescue is
grown on 14 million hectares, often develop signs of toxicosis during summer months
from grazing plants in fected by A. coenophialum. A more severe form of the
disease, fescue foot, has been associated with cold environment and reported in late
fall and winter months not only in the southeastern United States but also in the
northwest United States. In New Zealand, where perennial ryegrass is grown on 7
million hectares of pasture, sheep often develop a condition called ryegrass staggers
from grazing plants infected by A. lolii. New Zealand reports economic losses
grazing plants infected by A. lolii. New Zealand reports economic losses associated
with the sheep industry of $205 million per year. In the United States, economic
losses associated with the beef cattle industry alone is estimated at $600 million per
year.
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 (EV) (appendix 1) and lolitrem B (appendix 2), associated with the
diseases of fescue foot and PRGS respectively. Fescue foot was experimentally
induced in cattle under barn studies in the spring with 825 ppb ergovaline. The
ergovaline contaminated feed was given for a period of 42 days. Similar barn
studies in sheep in spring to early summer did not produce clinical fescue foot with
up to 1215 ppb. Field studies of natural fescue foot in a herd of sheep were
conducted, (ie 540 ppb) values of ergovaline in the feed, but clinical disease was not
produced in late fall through winter. A case study from a herd of sheep revealed 813
ppb dietary ergovaline had produced fescue foot in the months of fall (November).
Fields of perennial ryegrass (PRG) where sheep received 2,135 ppb lolitrem B
toxin were associated with clinical cases of PRGS in 42 sheep of 237 sheep (18
percent incidence rate) in the Willamette Valley of Oregon. Three months later,
sheep on this same field which then had 1,465 ppb lolitrem B, did not have PRGS.
These were the first range finding experiments undertaken in this locale to document
threshold levels of endophyte toxins associated with fescue foot and PRGS. / Graduation date: 1994
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35887 |
| Date | 13 August 1993 |
| Creators | Tor-Agbidye, John |
| Contributors | Craig, A. Morrie |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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