Detection of zeranol in the blood of ram lambs by a radioimmunoassay technique

Veterinary Research Laboratories, Stormont, Belfast, Northern Ireland.

Plasma separated from jugular blood samples from six weaned ram lambs was examined for zeranol after the lambs had been implanted, behind the left ear, with a 12 mg pellet. The results showed that the ipsilateral vein contained significantly more zeranol for up to 100 days after implantation; by 145 to 175 days the difference between the ipsi- and contralateral veins was no longer significant. Massage of the implant site did not increase the rate of release of zeranol from the residual mass.