Variation in ptaquiloside content in bracken (Pteridium esculentum (Forst. f) Cockayne) in New Zealand.

AIM: To examine stands of bracken fern (Pteridium esculentum)
from throughout New Zealand for the presence and concentration
of ptaquiloside (Pta), and to compare the presence and/or
concentrations of Pta in areas where bovine enzootic haematuria
(BEH) and/or acute haemorrhagic syndrome (AHS) has been
known to occur with those where BEH/AHS has not been recorded.
METHODS: Stands of bracken fern were sampled from 275
sites throughout New Zealand. Sixty-two stands were from a
regional survey predominantly from the Waikato and Coromandel
regions, 27 were from a farm in the King Country where
BEH/AHS had been investigated previously, and 186 were from
a national survey of the North and South Islands. Sampling
sites were from a mixture of grazed paddocks, roadsides, and
forest and bush areas. Samples comprised whole young fronds,
the tops of unfurling young fronds, or, for the Regional Survey,
mature green fronds from the previous season. Pta was extracted
from the samples, and measured using high-performance liquid
chromatography. Information on the occurrence of BEH/AHS
at specifi c locations was obtained from published information
and records from animal health laboratories in New Zealand.
RESULTS: The 275 samples contained widely varying concentrations
of Pta. In the Farm Survey, concentrations ranged
from 280–13,300 (mean 3,800) μg/g (on a dry-weight basis)
in the 63% of samples that contained Pta. A high proportion
of samples from the Regional and National Surveys covering
large areas of the country contained no detectable levels of Pta.
The majority (61%) of samples from these two surveys which
contained Pta were from areas where BEH/AHS was reported to
occur. Combining data from all surveys, in areas with reported
BEH/AHS, 42% of samples collected contained Pta, compared
with 6% where BEH/AHS was not known to occur.
CONCLUSIONS: Concentrations of Pta in bracken in New
Zealand vary greatly, and in a high proportion of stands Pta
is not found. A higher incidence of Pta, and some very high
concentrations, are found in areas where BEH/AHS was known
to occur.