Metabolism of halofuginone in rats and sheep fed excreta from poultry administered halofuginone orally

The fate of halofuginone and its metabolites from poultry when they were refed to rats was investigated. During a 6 d accumulation period rats excreted .607 uCi or 53.8% of the administered dose in the feces. The urinary output accounted for .157 uCi or 13.7% of intake. The rats respired 1.5% of the administered 14 C. Level of radioactivity in the tissues after the accumulation period was not significantly different from that found in control animals.

After the accumulation period the withdrawal pattern of halofuginone was investigated using two withdrawal times, 5 and 10 d. During the 5 d withdrawal period the rats excreted .105 uci in the feces and .03 uCi in the urine, or 9.5 and 2.7% of intake, respectively. By 24 h post-withdrawal, levels in the feces did not differ significantly from the controls. The amount of radioactivity in the urine, however, remained higher (P<.05) than in control animals. The greatest amounts of 14 C were found in the kidneys but tissue levels did not differ from levels in control animals. During the last 5 d of withdrawal fecal excretion accounted for 1.2% of intake with the urine contributing .7%. Levels of 14 C, significantly higher than the control, continued to be excreted in the urine. The kidneys contained modest amounts of radioactivity, although not significantly different from the control. By d 10 of the withdrawal period, 92.3% of the 14 C intake had been accounted for in the rat study.

A sheep study was conducted using wether lambs consuming a silage composed of 60% excreta, 20% ground hay, 10% ground corn and 10% dry molasses. The feces contained detectable levels of the drug. Sheep were slaughtered after a 16 d accumulation period. None of the analyzed tissues except the eyes contained halofuginone. When the remaining sheep were started on a withdrawal period, the halofuginone disappeared from the feces between d 3 and 4. No traces of halofuginone were found in tissue samples from sheep slaughtered 5 and 10 d post-withdrawal.