In 2010 we had a severe outbreak of Botulism on two of our clients’ farms.
In all, 22 animals were lost.
These were dairy cows grazing contaminated pasture, and beef animals of all ages strip grazing fodder beet.
Botulism is a poisoning caused by the ingestion of neurotoxin contaminated food.
The neurotoxin is produced by Clostridium Botulinum.
Disease in cattle is primarily due to types C and D, which will only grow and produce toxin in decomposing carcasses or vegetation.
Poultry litter is an ideal environment for this, but it also grows in dead rats, birds, and maggots in silage, hay and other feeds.
These are the most potent toxins known, with just a few nanograms (less than one millionth of a grain of sugar) needed to cause illness.
The dust from contaminated litter can be dangerous for cattle if spread on a windy day.
Small pieces of carcase can be transferred onto pasture and neighbouring lands by scavenger animals such as foxes, dogs and crows.
The toxin, once ingested by cattle is carried by the bloodstream to the peripheral nerve endings, where it blocks the passage of signals down the nerves.
This results in a flaccid paralysis, which usually starts in the hind quarters, moving forward to the front quarters, neck and head.
Cattle of all ages are susceptible to botulism.
The clinical signs include sudden death, knuckling, tongue paralysis, drooling, rumen stasis, bloat, slowing of the heart rate, diarrhoea, constipation, pupillary dilation, decrease in muscle tone of the tail, decrease/ absence of pedal reflexes and anal reflexes and sweating.
It must be remembered that all of these signs will not appear in each animal, nor indeed in each outbreak.
Affected animals lie down and are unable to rise, even under severe provocation.
Death occurs within 24 hours to several weeks, depending on the amount of toxin ingested.
There are no specific post mortem lesions.
Laboratory confirmation is difficult and rarely achieved.
There is no practical treatment in the bovine, and euthanasia is indicated on welfare grounds.
There is no vaccine available.
For a veterinary surgeon, it is not a legal requirement to report suspect cases of botulism, as it is not a notifiable disease.
However, it is best practice to notify the local DVO.
While samples can be taken and frozen within the first hour after death, it is best to record clinical signs in the live animal, and take blood samples for laboratory analysis.
Best practice indicates that we try to identify possible sources of toxin, and urge the client to remove all animals from the area where the toxin is believed to be, as a matter of urgency.
There a number of precautions that should be taken by a farmer who is dealing with chicken litter.
These are specified in a publication by the Department of Agriculture, entitled “Good Farming Practice”.
These precautions are aimed at keeping scavangers away from carcases and giving guidelines on the safest methods of spreading chicken litter.
Notably it should not contain carcases, nor be spread on a windy or warm day.
It should be deep ploughed into arable ground immediately.
Do not use the land for grazing cattle, harvesting silage or hay within twelve months of the spreading of litter.
There should be a three-year interval between spreading of litter.
In certain regions, there is now a practice of storing this chicken litter in special scavenger-proof houses, and incinerating it to heat the chicken house for the next batch of chickens.
This sounds like a very practical solution to the problem.
In any case I think it is against all animal welfare practice to continually allow innocent cattle undergo the horrendous suffering and death inflicted upon them by negligent spreading of chicken litter.
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