Effect of terbufos poisoning on the blood cholinesterase and hematological values in a dairy herd.

This report describes the effects of a sublethal dose of terbufos (counter 15G formulation) in a dairy herd. Ingestion of terbufos depressed whole blood cholinesterase activity. No recovery of this enzyme was evident until 30 days after ingestion after which a constant rate (0.65%/day) increase was observed.There was a good correlation between blood cholinesterase levels and clinical signs. Normal cholinesterase levels were reached at approximately 150 days after exposure. Cholinesterase levels in animals, ill prior to exposure, were slow to recover, while levels of healthy cattle surpassed those of control animals. Anemia was observed in some cows at approximately 30 days after exposure. The degree of anemia paralleled the severity of poisoning. The increase in packed cell volume paralleled the return of blood cholinesterase activity.