University of Missouri researchers found that tall fescue growers may
be able to reduce endophyte toxin concentrations by making hay or
ammoniating hay vs. feeding livestock green chop or silage or grazing
Tall fescue infected with endophyte at greater than 80% was harvested
in autumn at the University of Missouri Southwest Experiment Station
near Mt. Vernon. The fescue was fertilized with nitrogen at 75 lbs/acre
in August, then was clipped in mid-October. Four treatments were
studied, including green chop, ensiled forage, hay and ammoniated hay.
The green chop forage was frozen immediately after clipping. Ensiled
forage was allowed to wilt to 55% moisture, then was wrapped in
air-tight plastic bags and stored for six weeks. Hay was allowed to
sun-cure to 16% moisture, then was baled. Ammoniated hay was made by
sun-curing hay to 16% moisture, wrapping dry hay in air-tight plastic
bags, treating with 3% anhydrous ammonia, and storing for six weeks.
The green chop tall fescue contained 1,240 parts per billion (ppb)
ergot alkaloids and the ensiled tall fescue contained 972 ppb ergot
alkaloids. The hay and ammoniated hay contained much lower levels.
Ergot alkaloid concentrations in normal hay averaged 373 ppb, a level
lower than typical spring hay. The researchers speculate that this was
probably due to its lack of endophyte-containing stems and seed heads.
Ergot alkaloid concentration in ammoniated hay was 247 ppb and
statistically similar to the non-ammoniated hay.
Though this study did not include a feeding trial, other research
indicates that endophyte-infected tall fescue is toxic when ergot
alkaloid concentrations reach these high levels. Tall fescue produces
symptoms of toxicosis when ergovaline, the most highly concentrated
ergopeptine alkaloid, reaches 200 to 300 ppb.
The high concentration of ergot alkaloids in silage offers an
explanation for poor performance when calves are fed ensiled
endophyte-infected tall fescue. In addition, it indicates that an
entire class of alkaloids is preserved in the ensiling process, because
concentrations in the silage were similar to those in the green chop.
The low concentration in the ammoniated hay partly explains why
livestock consuming ammoniated endophyte-infected tall fescue hay show
few symptoms of fescue toxicosis.
Follow-up studies are under way to determine if spring-harvested hay
and ammoniated hay contain significantly different concentrations of
Source: Craig Roberts, Nick Hill and Robert Kallenbach, University of
Missouri and University of Georgia, as reported in University of
Kentucky Forage News.