Effects of copper pretreatment upon toxicity of selenium in ponies

Thirty-four adult ponies were used to determine the effects of single oral doses of copper (Cu) supplements (0, 20, and 40 mg of Cu/kg of body weight) on the toxicity of oral doses of selenium (Se) supplements (0, 2, 4, 6, and 8 mg of Se/kg of body weight) administered 24 hours after the copper was given. Signs of Se toxicosis-sweating, diarrhea, tachycardia, tachypnea, mild pyrexia, lethargy, and colic-developed in ponies given 6 and 8 mg of Se/kg of body weight without Cu pretreatment. Two of 4 ponies given 6 mg of Se/kg and both ponies given 8 mg of Se/kg without Cu pretreatment died within 36 hours after being given the Se. All ponies given either 20 or 40 mg of Cu/kg were unaffected by the subsequent Se supplement, regardless of dosage. The Cu pretreatment did not seem to inhibit absorption of Se, based on serum Se concentrations, but hastened the disappearance of the Se from the serum.