Synthetic phytohormones, phenoxy derivatives of fatty acids used as herbicides.
Animals most affected
Dogs, cattle, (other animals).
Compounds in this category
2,4-D, 2,4-DB, 2,4-MCPA, 2,4-MCPB,
2,4,5-T, dichlorprop, fenoprop, mecoprop.
Very widely used translocated selective herbicides; used for the control of weeds
in cereal crops, grasslands and meadows, and to clear undergrowth. Available in the
form of concentrated emulsions or soluble concentrates for dilution in water.
Poisoning can occur for one of two reasons:
Direct poisoning: through accidental ingestion of the agrochemical product itself;
recently treated vegetation, however, is of low toxicity and when the compound is
applied according to the manufacturers' instructions, it is not considered to be
harmful to animals.
Indirect poisoning: by ingestion of toxic plants which have been treated with
phenoxy acids. This unusual situation arises because:
the chemicals render more palatable plants which are normally avoided by grazing
animals (e.g. colchicum or autumn crocus, dog's mercury, etc.), or cause the
dried toxic plants to loose their bitter taste;
they increase the potency of the toxic principles in plants (e.g. increase the
levels of nitrate in beet).
Generally of low toxicity; for specific information
see individual compounds. Practically non-toxic to fish.
anorexia, ruminal atony, occasionally
depression with muscular tremor (often
of the hind limbs).
symptomatology varies slightly from that
described for ruminants, with anorexia, occasionally vomiting and diarrhoea;
apathy, ataxia and sometimes paralysis
of the hind quarters.
Death may occur once the animal has become
comatose or prostrate.
congestion of the gastrointestinal tract;
hepatic and renal degeneration;
petechiae on the conjunctivae, heart and brain.
No antidote. Symptomatic care only, promote
hepatic protective agents;
gastric or ruminal contents;
samples of urine or plasma.