Mexico's Ministry of Agriculture, Livestock and Fisheries (SAGARPA) has identified the cause of death of 600 head of cattle in Actopan, in the central-eastern region of the country, as high levels of urea in the feed, reports ProMED.

The source of the urea was thought to be poorly processed poultry litter, which is an acceptable feed ingredient for ruminants when properly processed, and is reported to have been included in the feed blamed for the deaths.

The ProMED moderator comments that much of the nitrogen in poultry litter is in the form of non-protein nitrogen (uric acid, urea, and ammonia), which is converted into protein by microorganisms in the rumen.

The same commentator adds that urea toxicity may be a problem in cattle if it is fed at excessive levels.

Whilst not wishing to cast doubt on the official findings, there is another possible explanation which has not yet been ruled out, according to these reports.

Botulism is a potentially fatal disease of cattle, caused by toxins produced by the bacterium, Clostridium botulinum. It has frequently been associated with the consumption of poultry litter, which has either not been properly processed or where the cattle or sheep have grazed pasture on which untreated litter had previously been spread.

In Northern Ireland last year, there was a series of cases of botulism in cattle and one in a sheep. Tests carried out by the Agri-Food and Biosciences Institute’s (AFBI) Veterinary Sciences Division (VSD) provided strong circumstantial evidence that broiler litter was a risk factor for many of these outbreaks.

C. botulinum bacteria are commonly found in the environment and will grow to high levels in decaying organic matter, including animal and bird carcasses. It is believed that contamination of broiler litter with the carcasses of chickens that have died from various causes during production can render the litter dangerous for ruminants, commented AFBI.

Cattle and sheep of all ages are susceptible to botulism, which is characterised by a progressive muscle weakness (paralysis). Affected animals may be weak, stagger about, or go down.

Cattle characteristically display flaccid paralysis and occasionally protrusion of the tongue. In most cases, the disease is fatal.

Other cases of botulism in recent years have been reported in north-west England, western England, and in Australia in New South Wales. The authorities in Queensland warned about the possibility of the disease following the floods there a year ago.

The investigation of the cattle deaths in Mexico is continuing, according to a federal official with the agriculture ministry there.

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