Effects of activated carbon, phenobarbital, and vitamins A, D, and E on polybrominated biphenyl excretion in cows.

Twelve cows environmentally contaminated with polybrominated biphenyl residues were in a balanced two-period changeover experiment. The treatments were activated carbon and sodium phenobarbital; sodium phenobarbital and injections of vitamins A, D, and E; activated carbon, phenobarbital, and vitamins A, D, and E; and control. A standard roughage and concentrate diet was fed. Average initial concentrations of polybrominated biphenyls in the milk fat ranged from 92 to 236 ppm. The experimental treatments did not affect significantly excretion of polybrominated biphenyls in milk and feces or the apparent half-life of residues in milk fat averaged 60 days but ranged from 36 to 301 days. The longer half-life in early lactation than in later lactation indicated an effect of change of body weight on half-life. Milk was the major route of excretion, averaging 6.5 times that of fecal excretion. Polybrominated biphenyl in milk fat, body fat, blood, and feces followed parallel concentrations troughout the study.