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Ergot Poisoning

Ergot is a serious problem in feed this year. This parasitic fungus of the Claviceps genus starts its damage in the field, replacing one or more kernels in a mature grain head with a hard, dark mass called a sclerotia. In addition to reducing yield, the fungus produces a number of poisonous alkaloids toxic to cattle, pigs, poultry and horses.

Cool, wet weather favours ergot. So it’s not surprising that reports of higher than normal levels of contaminated grain are showing up right across the Prairies. It was almost guaranteed by last year’s wet spring combined with a prolonged flowering period for grasses and cereals.

Wind blown spores infect flowering grains and grasses. Rye and triticale are most susceptible but ergot also shows up in barley, wheat and oats. As a result screenings purchased for feed may contain abnormally high levels. Some grasses can also be infected. Grasses around the headlands of fields are the most likely source of spores that carry the infection over from one year to the next.

The poisonous alkaloids produced by ergot affect animals in several ways. Pregnant females can abort and ergot related abortions have been reported in cattle, horses and pigs. Laying and breeder hens are also affected. The tolerance for ergot in pregnant or breeding animal rations is zero.

Toxic levels in rations will reduce the performance of growing and finishing stock, but the losses may not become apparent for six to eight weeks.

The classic signs of ergot poisoning are the effects it has on peripheral circulation. Sustained intake causes vasoconstriction, or shutting down the blood supply to the extremities. Over time, this results in gangrene and sloughing of the tail, ear tips and hooves. In chronic cases an entire foot or claw will be lost. Blood-starved extremities freeze in cold weather, compounding the problem. It is unlikely that animals affected to this extent will ever recover and animal welfare becomes an overriding concern.

How much is too much? There is no clear answer. Some nutritionists say the limit for pigs is zero. For all other species, it is one kernel per thousand or 0.1 per cent by weight (10 ergot bodies per litre of grain). Cattle will usually tolerate up to 12 grams of ergot per day with no adverse effect (10 ergot bodies weigh about one gram).

Some feed mills will not accept grain with ergot levels above 0.04 to 0.06 per cent (four to six ergot bodies per litre of grain). The risk associated with selling contaminated complete feeds and pelleted rations is high.

If you swath graze there is no easy way to assess the degree of ergot infestation. Barry Yaremcio, a beef forage specialist with Alberta Agriculture, advises producers to evaluate swaths field-byfi eld. Pull them apart and start counting ergot bodies, then make an educated guess. If a swath looks like it may contain borderline toxic levels, dilute it by feeding forage that doesn’t have any ergot. “When in doubt dilute it,” he says. “It’s better to be on the safe side.”

Ergot is a bane of human and animal health dating back to ninth century Europe when the fungus caused ergot epidemics. Today, almost 1,000 years later, it still remains a potential threat in Western Canada. Be especially careful in 2011.

About the author

Columnist

Dr. Ron Clarke

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).

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