NADIS disease bulletins are written specifically for farmers, to increase awareness of prevalent conditions and promote disease prevention and control, in order to benefit animal health and welfare.

Farmers are advised to discuss their individual farm circumstances with their veterinary surgeon.

Urea (ammonia) poisoning in cattle

There are two potential ways in which cattle can get access to urea. Firstly, urea is fed to cattle as a cheap source of nitrogen for the microbes in the rumen as an alternative to expensive rumen-degradable protein. Secondly, cattle can get access to poorly stored urea fertiliser. If urea is fed incorrectly in feed or cattle eat large amounts of urea fertiliser toxicity problems can occur.

Urea poisoning occurs when the cow takes in too much urea too quickly. Normally, bacterial enzymes convert urea to ammonia which is then taken up be the bacteria to produce amino acids, the building blocks of proteins. However if too much urea is eaten, the conversion to ammonia still occurs but much of the ammonia is not taken up by the bacteria. This ammonia is then absorbed across the rumen into the cow’s bloodstream. Most is dealt with by the liver, but if sufficient urea is fed the liver’s ability to detoxify the ammonia can be exceeded and toxicity results.

Clinical Signs

The signs are usually seen within an hour of eating the excess urea. The higher the dose the faster the signs develop.

¨ Salivation

¨ Frothing at the mouth

¨ Bloat

¨ Bellowing

¨ Twitching

¨ Abdominal pain

¨ Collapse

¨ Death

Diagnosis

The clinical signs are not definitive.

If your cattle are being fed urea or may have had access to fertiliser and they start showing strange signs get veterinary involvement as soon as possible.

There is no routine test that will identify urea poisoning. Ammonia testing of blood will confirm suspicions but the test is rarely done, difficult to do, and requires either fresh (<1 hour) or frozen samples.

There are no specific changes post mortem, however a proper examination post mortem will eliminate several other diseases that could cause these signs

Treatment

Severely affected cattle, particularly if they are recumbent, will not respond to treatment.

For less severely affected cases drench the cattle with 5L of vinegar followed by 20 to 40L of water. This will reduce the absorption of ammonia. It can be repeated daily until signs have disappeared

Prevention

Prevent access to urea fertiliser.

If feeding urea make sure that you:

1) Mix the urea supplement effectively

2) Feed the correct amount of urea – all calculations should be checked by at least two people.

3) Allow the animals to adapt to urea feeding by starting low and building up gradually.

4) Feed the urea continually without breaks.

5) Feed a high grain diet alongside the high urea diet as the carbohydrates enhance the conversion process from nitrate to microbial protein

Richard Laven PhD BVetMed MRCVS