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17 terms

Ionophore Feed and Water Related Toxicants - Toxicology

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What are the uses of ionophores?
anticoccidial in cattle, poultry and goats. growth promoter feed additive in cattle, reduction of bloat and rumen acidosis in ruminants, prevention of tryptophan-induced atypical bovine pulmonary emphysema.
What are ionophores?
Carboxylic acid derivative antibiotics, slightly soluble in water, organic solvents and oils. Form lipid soluble complexes with polar cations that are transported across membranes (Na, K, Ca, Mg). Include monensin, lasalocid, salinomycin, narasin, etc.
Which is the most common ionophore?
monensin
Which species is most sensitive to ionophore toxicity?
equines, followed by adult turkeys.
Concurrent administration of one of which 5 drugs increases ionophore toxicity?
cardiac glycosides, tiamulin, chloramphenicol, erythromycin, or sulfonamides
How much of ingested monensin is absorbed by ruminants? by monogastrics?
50% absorbed by ruminanats, monogastrics absorb most of it.
How is monensin metabolized/excreted?
rapidly metabolized in the liver and excreted in the bile. Except in equines, they can't metabolize.
Which species is most sensitive to ionophore toxicity?
equine, followed by adult turkeys
What is an ionophore's mechanism of action?
disrupt transmembrane electochemical gradients, main targets are mitochondria of highly energetic tissue. Influx of sodium-ionophore complex increasing intracellular sodium accompanied by increasing intracellular calcium. Sequestering of calcium means inhibition of mitochondria and decreased ATP/energy. Cell death, disruption of ion concentrations alters cell function.
What are the clinical signs in a horse with ionophore toxicity?
anorexia, profuse sweating, colic, depression, incoordination, hyperventilation, tachycardia, tachyarrhythmias, prostration, and death.
What are the clinical signs in poultry with ionophore toxicity?
anorexia, diarrhea, ataxia, resting on knees with wings and legs directed outward, decreased egg production.
What are the lesions associated with monensin toxicity in horses?
cardiac muscle lesions in horses (pale cardiac muscles, white streaks of necrosis in the myocardium), skeletal muscle lesions.
What is the method of lab dx of ionophore toxicity?
chemical analysis for ionophores, best sample is feed, method detects ppb levels.
What are your dfdx in a horse with signs of monensin toxicity?
colic, blister beetle ingestion (cantharidin toxicosis), azoturia
What are your dfdx in poultry with signs of monensin toxicity?
nutritional myopathy, coffee senna toxicosis, botulism, Na-water deprivation toxicosis, mycotoxicosis, round-heart disease, downer syndrome.
What is the treatment of monensin toxicity?
no specific antidote, remove source, decrease absorption with activated charcoal, mineral oil, saline cathartics. symptomatic treatment (fluids and electrolytes, monitor). Vitamin E and selenium may decrease muscle damage especially in cattle and swine.
What is the prognosis of ionophore toxicosis?
horses that survive may suffer myocardial scarring and necrosis, horses may not reach previous performance.