Pathologic changes associated with experimental lasalocid and monensin toxicosis in cattle

Area of Science:

• Veterinary Toxicology
• Animal Science
• Pathology

Background:

• Ionophores like lasalocid and monensin are commonly used in cattle feed.
• Understanding their toxicity is crucial for animal health and safety.

Purpose of the Study:

• To investigate the acute toxicity of lasalocid and monensin in Holstein steers.
• To identify gross and microscopic lesions associated with ionophore toxicosis.

Main Methods:

• 36 Holstein steers were administered single oral doses of lasalocid (1-100 mg/kg), monensin (25 mg/kg), or rice hulls.
• Animals were monitored for 32 days, followed by necropsy and microscopic examination of multiple tissues.

Main Results:

• Lasalocid was lethal at 50 and 100 mg/kg; monensin was lethal at 25 mg/kg.
• Both ionophores induced cardiomyopathy, characterized by gross (dilated heart, hemorrhages) and microscopic (myocyte necrosis) lesions.
• Early deaths (<3 days) showed pancreatic acinar cell degranulation.

Conclusions:

• Lasalocid and monensin exhibit significant acute toxicity in cattle at high doses.
• Cardiomyopathy is a primary pathological outcome of lasalocid and monensin toxicosis.
• Pancreatic changes may indicate early toxic effects of these ionophores.