Published Date: 1997-09-05 23:50:00
Subject: PRO/AH/PL> Sorghum ergot - Australia
Archive Number: 19970905.1908

SORGHUM ERGOT - AUSTRALIA
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A ProMED-mail post
Date: Thu, 4 Sep 1997 11:49:00 +1000 (Report issued 3rd September 1997)
From: Barry Blaney <BlaneyB@prose.dpi.qld.gov.au>
[see
Sorghum ergot (02) 970303142501
Sorghum ergot (03) 970429143535
Sorghum ergot (04) 970430160434
Sorghum ergot (05) 970502160414
Sorghum ergot, international meeting, 2-7 June 1997 970501155853
Sorghum ergot - Brazil, Argentina, Bolivia, Colombia, 970228151822
Sorghum ergot spreading - Americas 970725113446]
Sorghum ergot (_Claviceps africana_) associated with feed refusal and
impaired milk production in pigs and cattle in Queensland: research also
shows toxicity to chickens.
Sorghum ergot (_Claviceps africana_) was first identified in Australia in
April 1996, and within 6 months had been found in all sorghum-producing
regions in Queensland and New South Wales. Sclerotia of _C. africana_
produce a different range of alkaloids than the ergot of rye (_C. purpurea_),
the latter causing reduced growth and milk production in livestock and,
through impaired circulation, producing gangrene of the extremities. The
main alkaloid in _C. africana_ (dihydroergosine), has been reported to be
much less toxic to laboratory animals than rye ergot alkaloids. No
information was available on the toxicity of sorghum ergot to livestock, and a
request was made to this Department to investigate.
Ergot-infected grain was obtained in mid 1996 and incorporated into pig
grower diets that were formulated as well as possible to balance fibre and
predicted digestible energy (DE). Thirty-six pigs of each sex and two breeds
(LW and Duroc) were stratified by live weight and divided into six groups.
Each group was randomly allocated to one of six diets containing up to the
equivalent of 5% sclerotia by weight and fed these diets for 28 days in a
growth trial monitoring pig performance. The alkaloid concentration in the
5% ergot diet was about 0.005%, predominantly (>90%) dihydroergosine. Pigs
were bled on days 0 and 28 of the trial, and the samples analysed for
prolactin and general biochemical parameters. Feed consumption and live
weight were individually monitored.
There were no clinical signs of illness in the pigs, apart from one pig with
a mild abrasion of the footpad. Reductions in feed intake and poor feed
conversion was observed over the first 7 days with diets containing more than
0.6% sclerotia by weight, but some tolerance appeared to develop over time.
Over the full period of the trial, growth was reduced by 30% in pigs
receiving 5% sclerotia, largely as a result of poor feed intake and poor feed
conversion. A much more significant finding was that blood prolactin
concentrations were significantly depressed in pigs receiving 0.62% sclerotia
or greater and by >80% in pigs receiving the highest ergot level, clearly
indicating a potential to interfere with lactation.
At the same time as the prolactin results became known (mid-August 1997),
reports were received from piggeries in central Queensland, of severe feed
refusal and death of piglets. The extent of feed refusal varied from farm to
farm, at worst depressed by about 50%. Sows were reported as farrowing
normally and producing apparently healthy piglets but failing to lactate.
Apart from one report of possible still-births on one farm, and one abortion
on another at about the time the sorghum ergot was fed, most piglets walked
and breathed but could not access milk and died within a few days. Samples
of grain from these piggeries contained from 1-5% by weight of sclerotia.
Concentrations of alkaloid in the diets were around 0.002-0.004%,
predominantly dihydroergosine. At least 6 piggeries were affected. One farm
that continued feeding ergot lost 12 litters, while others that replaced the
feed within 2/3 days minimised losses. The affected sows had completely
empty udders and recycled to the boars. In conjunction with the experimental
evidence of reduced prolactin levels, it appears to be proven that sorghum
ergot can have the same affect in reducing milk production as rye ergot.
This was not expected in view of previous publications indicating that
sorghum ergot had no effect on lactation in mice.
At the same time and the same area in central Queensland, several dairy farms
reported feed refusal and drops in milk production associated with sorghum
ergot feeding. Ergot in the grain portion of the ration also ranged from 1-
5%, but the animals received the bulk of nutrients from rye grass pasture.
Because of other variables, the actual role of ergot requires further
investigation. In a preliminary trial with beef cattle grazing a sorghum
crop in which ergots comprised about 0.3% of the total dry matter intake, no
clinical signs associated with ergot alkaloid poisoning were observed and the
animals maintained liveweight. However, there were inconsistent but
significant reductions in blood prolactin, indicating the potential for
reduced milk production by cattle.
No reports have been received of problems with sorghum ergot in commercial
chicken flocks, but [only?] one feeding trial has been performed. Meat
chickens were fed the equivalent of up to 5% ergot sclerotia from 3 to 23
days of age. Diarrhoea was observed in up to 31% of the birds fed 5%
sclerotia, and mortality at this concentration was 21%. In a few cases,
death was preceded by apparent gasping for breath. Growth of surviving birds
was reduced by about 8% compared to controls. Diarrhoea was also significant
in birds fed 2.5% sclerotia, but reduction in growth overall compared to
controls was slight. Diarrhoea is among the effects noted in cocks dosed
with ergotamine and related alkaloids, and gasping for breath has been
reported in rodents given ergosine and related alkaloids. However, these
effects have not been reported to occur with dihydrogenated derivatives such
as dihydroergosine.
As a conservative interim measure pending more observations, a level of 0.3%
sorghum ergot has been inserted in Queensland Stockfood Regulations.
Observations to date indicate that crops planted at the recommended time in
Queensland have very low levels of contamination, perhaps 1-10 sclerotia/kg
grain (0.002 - 0.02%). The problems in piggeries and dairies appears to be
localised to a few very late-planted crops which flowered during cool weather
in April. Grain from these crops had relatively high levels of sclerotia (1-
5%). Early-planted crops in southern Queensland, which flower between
December and mid-March are expected to escape the worst of infection, but the
disease will restrict cropping practices such as flexible planting dates and
ratooning in central Queensland. Further research will be carried out to
determine the impact of ergot on pregnant and lactating sows, dairy cattle,
laying and broiler chickens and feed-lot cattle.
---
Barry J. Blaney & Malcolm Ryley
Queensland Department of Primary Industries,
Locked Mail Bag No. 4
Moorooka, Queensland 4105
Australia
e-mail: <blaneyb@dpi.qld.gov.au> or <ryleym@dpi.qld.gov.au>
..........................................................................chc
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