CASE NOTES

Virginiamycin and ad lib Sodium Bicarbonate
in the Treatment of Grain Poisoning in Sheep

Tony Morton , District Veterinarian,
Hume Livestock Health and Pest Authority

HISTORY

A mob of 562 merino ewes sheep that were supplemented with barley in the weeks before consignment were sent to agistment 09.01.2009.The mob was reported to have 55 dead on the evening of 12.01.2009. A count a few days later revealed 73 sheep had died with a further 14 unaccounted for. After delivery, the sheep were agisted on stubbles.

When the property was visited on 13.01.2009 there was evidence of grain spills (wheat) and access to a small area of thin unharvested triticale. In my experience and that of other DVs it is extremely unlikely that a thin standing crop would cause a massive mortality due to grain poisoning.

It was an extremely hot day with the car thermometer registering between 40-44c during the visit which meant even sheep in healthy mob sent to agistment at the same time were lethargic. In the heat of the day it was assessed that at least 50 -70 had symptoms of depression &/or scouring & /or sore feet. When the temperature dropped and the sheep were driven the number affected was clearly much higher.

POST-MORTEM FINDINGS

The vast majority of dead sheep were decomposing making a definitive PM impossible. A very dead sheep with the rumen split open had massive amounts of grain in the rumen.

PM of the freshest dead sheep was a classical chronic grain poisoning with severe rumenitis and marked inflammation of the overlying omentum but there was very little whole grain remaining in the rumen (impossible to say if wheat or triticale) as the intake would have been Friday and I investigated Tuesday. Autolysis was too advanced for confirmation of the diagnosis by histopathology.

TREATMENT / CONTROL

The afternoon (night) of my visit as conditions cooled the owner moved the mob and realised nearly half the mob were ill. He drenched the worst 220 head with Eskalin (2 sachets made up to 3 litres per 100 head and dosed at 10 ml per head) to suppress the production of acid from the fermenting grain. This is an off-label use requiring a veterinary prescription. Starting at 7.00pm this was all that could be achieved in the way of treatment before dark.

The following morning the worst half of that group were again drenched with Eskalin and given a shot of LA tetracycline IM to control infection in the damaged rumen wall.

Both groups of sick sheep (2 x 110) were provided with sodium bicarbonate in loose licks as well. The owner decided to use calcium molasses blocks as a decoy to get the sheep to the bicarb and within 30 seconds of licking the block they were avidly licking the loose bicarb.

The less severely affected 110 ate considerably less bicarb. The owner reported only two sheep died post treatment.

DISCUSSION

I do not recall ever seeing a significant grain poisoning when sheep were given access to standing crop (e.g. the header couldn't go under trees or near rocks or gullies were too wet) and that has been the experience of many other DVs with the exception of heavy grain spillage from the standing crop, massive rice crop (10tonne/hectare) and one case based on the farmers report (several DVs including myself report diligent searching has found grain spills in these cases). I believe the source of the grain poisoning was the spills detected and possibly other spills we did not find.

In an extraordinary example of 'nutritional intelligence' or self medication the owner reported the worst affected mob of 110 ate about half a bag (10 kg) of bicarb that day. This is close enough to 100g/head/day which is a much bigger intake than you could readily give (drench) even a small number of sheep.

In recent years when confronted with grain poisoning in sheep (usually at a much earlier stage than this) I have adopted the strategy of immediately drenching the whole mob with Eskalin to prevent further production of acid, providing sodium bicarbonate as a loose lick which sheep will often voluntarily consume and then attend to the worst affected sheep with individual additional drenches of sodium bicarbonate and long acting injections of oxytetracyclines to control infection in the rumen wall. Farmers using this Eskalin drench /sodium bicarbonate ad lib strategy have all reported good results since I started using it in 2006. Similarly other DVs have reported favourable results.

This case and the experience of other district veterinarians gives further evidence of the usefulness of drenching with Eskalin and providing sodium bicarbonate as a loose lick for grain poisoning outbreaks. The strategy had also been used with success in cattle (pers com Shaun Slattery, DV Narrabri).

 

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