Recognizing toxicosis in cattle

Poisoning in food animals is infrequent occurrence but often explosive in scope, says Stan Casteel, DVM, PhD, Dipl. ABVT, University of Missouri. Speaking at the 2011 Annual Western Veterinary Conference, Casteel discusses some toxic substances that are often implicated in cattle poisoning, and their clinical signs that might point a veterinarian to a toxic cause of illness or death.

Lead can be found in batteries, paint (pre-1960) (burning concentrates Pb), solder, weights, bullets near joints, and industrial sources such as lead smelters, mine tailings, and perhaps used motor oil.

Lead poisoning has an onset of days to a week. Central nervous system (CNS) dysfunction is a hallmark in cattle with lead poisoning, and cattle can also display gastrointestinal signs. Death from lead poisoning can occur in 1-10 days.

Differential diagnosis: Thiamine responsive polioencephalomalacia, water deprivation, meningitis.

Arsenic can be found in insecticides (arsenates), herbicides (arsenites, monosodium methanearsonate), defoliants/desiccants, fungicides, wood preservatives and CCA treated wood.

Arsenic toxicity onset is typically in 6-12 hours of ingestion. It can cause sudden death from cardiovascular collapse in some cases. Most affected animals show colic, weakness, trembling, salivation, subnormal temp, rumen atony, watery diarrhea dehydration, prostration, rapid heart rate and respiratory rate, and terminal seizures. Occasionally just a "depressed loner" might be observed.

Organophosphate and carbamate insecticides
Organophosphates (OP) are derivatives of phosphorous used as insecticides on plants and animals and nerve gases. Several dozen are currently in use. Carbamates are derivatives of carbamic acid and are in insecticides used in plants and animals. A few dozen are in use.

Clinical signs of OP or carbamate poisoning include muscarinic effects such as bronchoconstriction, salivation, bradycardia, urination, diarrhea, bloating and miosis. Nicotinic effects such as muscle fasciculation, stiffness, ataxia, weakness and paralysis. CNS effects (primarily OP) such as restlessness, stimulation then depression especially of respiratory center can also be observed.

Sodium Chlorate
Sodium chlorate is a non-selective herbicide used as soil sterilant and cotton defoliant. Its salty taste is attractive to cattle.

The onset of sodium chlorate toxicity can occur in several hours. Clinical signs include dyspnea, coli, methemoglobinemia, hemoglobinuria, prostration and terminal convulsions.