Sorghum Diseases in India

Experimental feeding of the suspected toxigenic
material to pregnant and lactating sows clearly
implicated the ergot sclerotia, contaminating the
grain at the rate of approximately 1-2%, in reproductive
failure due not to any detectable effect
on the foetus in utero, but to inhibited
mammary function leading quickly to starvation
of normal piglets born at normal term. Evidence
of peripheral vascular disturbance, commonly
associated with the classical ergot fungus of
temperate cereals and grasses (Claviceps purpurea)
was never expressed.
Most of the pharmacological properties of ergot
sclerotia (Claviceps spp) can be attributed to
the ergolene alkaloids derived biosynthetically
from a common pathway of secondary metabolism
commencing with the condensation of tryptophan
with the isoprene precursor dimethylallyl
prophosphate. Claviceps purpurea elaborates
the most complex derivatives of lysergic acid,
but C. fusiformis completes only part of the pathway,
the clavine alkaloids, agroclavine and
elymoclavine accumulating instead as endproducts
occurring at about 0.3% (w/w) of the
sclerotial tissue and as trace amounts even in the
honeydew exudate associated with sphacelial
fructification. Pure alkaloids of this type, extracted
from sclerotia grown on pearl millet or produced
by the fungus in fermentation, exhibit
negligible peripheral pharmacology but are
potent central stimulators (Mantle 1968a). For
example, mice given daily approximately 0.5 mg
agroclavine in food became obsessively hyperactive,
tearing blotting paper on which they
were bedded into minute shreds. Sheep given 40
mg agroclavine subcutaneously persistently
licked the walls of the pen for 2 to 3 hours, an
expression of quite atypical behavior. In contrast,
at a dose of 350 mg day -1 (which elicited no
overt signs), pregnant mice failed to prepare for
lactation and pups died of starvation. At a lower
dose, lactation was almost switched off, being
sufficient only to support one grossly malnourished
pup whose eyes were still closed at 4
weeks of age and whose weight was less than
one fifth of the weight of a normal animal at 3
weeks of age. When the higher dose was given
to lactating mice, lactation was switched off and
the pups ceased to thrive. When a similar dose
was given to mice on days 3, 4, and 5 after insemination
blastocysts failed to implant and
pregnancy did not establish (Mantle 1969).
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These findings pointed to an endocrine-mediated
mechanism which logically results from
central (hypothalamic) stimulation causing, in
the mouse or rat, a diminution of prolactin release
from the pituitary gland and the consequent
paucity of lactogenic stimulus. Prolactin
being also a luteotropic hormone in these experimental
animals, its absence leads in turn to insufficient
progesterone to prepare the uterus
wall for blastocyst implantation.
Striking though these effects are in the mouse
or rat, without eliciting any overt signs of altered
behavior, it was not possible to produce
similar agalactia in either the goat or the cow
where relatively small changes in lactation performance
are comparatively easy to monitor.
Further, the known differences in mechanisms
of endocrine control of pregnancy in laboratory
rodents and the human do not allow confident
prediction that any notable reproductive hazard
could be ascribed to lightly ergotised millet as a
human food. Although apparently no experiments
on the effect of clavine alkaloids on lactation
in the pig have been reported, the close
mimicking of the Rhodesian porcine agalactia by
the mouse implies that the pig is at least sensitive
to the inhibition of prolactin release with
respect to its role in initiating and maintaining
lactation. The conclusion, therefore, is that while
ergotised millet may be undesirable for human
consumption, any effects are not likely to involve
serious hazard. Nevertheless, what might
be assumed to be a potentially reasonable outlet
for substandard grain, namely as pig feed, is
certainly contraindicated for pregnant (near
term) or lactating sows. Since species other than
pigs (e.g., buffalo, goat, donkey) may be more
usually available in millet-growing areas subject
to ergot epidemics, there is a clear need for the
results of research on their tolerance of ergot to
be published in the most relevant scientific literature.
An even wider market concerning feed
for poultry or fish could well be explored to advantage.
Ergot has acquired a toxigenic image
which is partly well justified (Mantle 1978) but
which must not be allowed to be a basis for unreasonable
and unscientific extrapolation across
the whole range of Claviceps spp. While Claviceps
purpurea deserves the maximum caution, C. fusiformis
on millet commands less concern unless
contamination exceeds about 1%. There are
grounds to believe that ergot disease of sor-