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| Flowering bog asphodel |
Farmers and
land managers have been in touch with the Heather Trust over the past few
months to express their concerns about the links between sheep disease and wet
ground.
Yellowses has a number of regional names like saut and plochteach, but it
is widely known for causing painful symptoms resembling extreme sunburn, as
well as the complete loss of sensitive extremities like ears. In extreme cases,
sheep are blinded and lambs are killed. Research suggests that the disease is caused
when sheep ingest toxins which attack the liver and cause dangerous chemical
build-ups in the body, and the culprit responsible for these toxins is widely
believed to be bog asphodel.
Asphodel is
a native plant found on wet hill ground with a pretty yellow flower which shows
mainly after midsummer. Sheep feeding on asphodel during the early summer months
are most likely to show symptoms, and the only treatment is currently to
restrict grazing where possible. Seriously affected animals can be brought into
the shade where their sunburn-like symptoms are less of a problem, but this is
seldom practical in the summer months on hill farms where sheep should be
getting the benefit of the grass and indoor housing may be unsuitable or
non-existent.
The precise
relationship between asphodel and yellowses is not totally clear, and many
sheep are grazed happily on wet, asphodel-covered hill ground all summer
without any ill-effect at all. At the same time, some of the worst areas in
Norway can see up to 50% of lambs killed during sunny summers, and the disease
can be a real problem for many upland farmers. The picture is confusing, but
asphodel has been linked to other diseases in sheep and cattle over the years,
and the plant’s latin name (Narthecium
ossifragum) reflects the traditional belief that eating it would give sheep
brittle bones, although modern thinking tends to relate this symptom with a
general shortage of Calcium in the kind of environment where asphodel thrives.
As land
managers are encouraged to engage with important peatland conservation and
restoration work, the likelihood is that wetter moors will increase the amount
of asphodel available for sheep, and research is underway to learn more about
how the disease impacts on livestock. At the same time, wetter moors might also
be linked to increased challenges to heather coverage, including the prospect
of heather beetle outbreaks which are sometimes linked to moisture content. If
we are aiming for a wetter future in the uplands, now is the time to find out
what the knock-on effects may be for other land uses.
More
information on yellowses is available in an article written by the SRUC’s Davy
McCracken in the Heather Trust’s annual report from 2016.
