Urea poisoning in Ruminants

Fig: Urea poisoning in a cattle

To review, urea is a common source of non-protein nitrogen (NPN) used as a feed supplement in ruminants. The rumen microflora utilize the nitrogen in urea released as ammonia to make protein which then is absorbed and utilized by the animal for growth metabolism.
Because ammonia is toxic, balancing the ration with the appropriate amount of urea is essential. Slight excesses of urea can be handled in normal ruminants as the ammonia absorbed from the rumen will be converted back to urea in the liver and then secreted by the kidneys into the urine. The trouble arises when this safety mechanism is overwhelmed and ammonia accumulates in the blood to dangerous and often lethal levels.
Depending on the level of excess urea in the feed, illness may appear within minutes to several hours following ingestion. Onset and progression may be so rapid that animals may simply be found dead. Clinically ill animals may display twitching of facial muscles and ears, teeth grinding, excessive salivation, bloat with abdominal pain, and forced breathing that often progresses to weakness with a staggering gait and later, recumbence with terminal convulsive episodes.
A strong presumptive diagnosis of urea toxicity can be made during necropsy soon after death by the distinctive odor of ammonia when opening the rumen and an elevated rumen pH of greater than 7.5-8. Other post mortem lesions may include obvious bloat, pulmonary edema, and epicardial/endocardial hemorrhages.

Fig: Urea poisoning, Epidemiology, toxic dose,clinical and postmortem findings, diagnosis and treatment.

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