Feed & water related toxicants: Ionophore Dr. Shokry Flashcards
What are ionophores?
Most common?
carboxylic acid derivative antibiotics
anticoccidial in cattle, poultry (except turkeys) & goats
growth promoter feed additive in cattle, improves milk efficiency in dairy cattle
Monensin, lasalocid
susceptible spp
sensitive spp
all spp
horses most sensitive then turkeys
equines eating cattle dose not toxic
toxicokinetics of monensin
distributed thoroughout body but blood & tissue levels relatively small
rapidly metabolized by P-450 enzymes in liver. Horses have lowest oxidative demethylases of domestic sp. so slow metabolism by horses
Excreted in bile (Horses have no GB!)
MoA of monensin toxicosis
main targets = mitochondria of high energy tissues (myocardium, skeletal & kidney)
incr intracellular Na accompanied by incr of intracellular Ca2+⇒ inhibition of mitochondria, decr ATP, incr cytoplasmic Ca = cell death
catecholammine release→ free radicals causing sarcolemmal membrane damage
Acute onset = Acute death like NPNs
CS of monensin toxicity
horses: severe GI & cardiac
cattle: GI
poultry: GI & CNS
dogs: CNS
lesions of monensin toxicity
mainly cardiac lesions in horses
mainly skeletal muscle lesions in sheep, swine & dogs (pale muscles)
both skeletal & cardiac mm lesions in poultry
diagnostics for monensin toxicity
Lab:
best sample is feed
GI contents, liver & feces may also be taken
Clin path: may see elevated CPK, ,AST (muscle damage indicators)
incr LDH & AlkP & PCV
may see decr Ca2+ & K during 1st 12 h but then normalizes
Ddx on monensin toxicity
Horses: Colic, Blister beetle ingestion (canthraidin toxicosis)
Cattle: Vit E/selenium def, poisonous plants (Coffee senna, Taxus spp, Vetch, Oleander, milkweed
Poultry: coffee senna, botulism, mycotoxicosis,
Tx for monensin toxicity
Px?
no specific antidote!
Decontamination/symptomatic
Vit E/selenium ? may help decr mm damage
POOR
