Feed and water related toxicants

[Bovine Toxicology]

Abstract

Seventy-two cattle were fed Rumensin at levels up to 100 g/ton for 160 days and no changes indicative of toxicity were observed for hematology, serum chemistry, urinalysis, or organ weight parameters. No gross or microscopic tissue changes relating to treatment were observed. The 100 g/ton level did, however, reduce gain.
Oral single doses of Rumensin fed to cattle has caused mortality at 55 mg/kg of body weight which is 80 times the recommended dose of 30 g/ton. However, no mortality ocurred at the 30 g/ton level.
The evidence has accumulated that feed containing 279 ppm monensin is lethal to horses and that 125 ppm may be toxic but not necessarily lethal. Feed with 31 ppm monensin did not cause any clinical changes, aside from partial anorexia in the horse. The single-dose toxicity studies indicate the LD50 of monensin for horses is between 2 and 3 mg/kg of body weight.