Distribution of conjugates of alkylphenols in milk from different ruminant species.

Conjugated alkyphenols in milk constitute a reservoir for species-related alkylphenols in dairy products. The distributions of conjugated alkylphenols between different conjugation pathways (sulfation, phosphorylation, and glucuronidation) were determined in cows', sheep's, and goats' milk. Species-related p- and m-cresols and 3- and 4-ethylphenols were found to be mostly conjugated with sulfate with minor amounts associated with phosphate and glucuronide conjugates in all milks. Similar distributions were observed for alkylphenols in the urine and milk from the same ewe. Phenol was present in minor amounts distributed sporadically between different conjugates in the milks. Sulfate-conjugated phenol was not detected in the ewe's urine, which included equal amounts of glucuronide and phosphate conjugates. The amounts of alkylphenols were different in sheep's milk from different sources suggesting that there were effects of feed, breed, and individual animal variation on the metabolism of alkylphenols.