Excretion, through milk, of ptaquiloside in bracken-fed cows. A quantitative assessment

Abstract

The content of ptaquiloside (ptaq), a major Pteridium aquilinum carcinogen found in milk from cows fed bracken in Venezuela, has been estimated quantitatively in its passage through bovines into milk. Six cows were given 6 kg/animal/d of fresh bracken fronds whose ptaq content was determined. Ptaq first appeared in milk 38 h after initially feeding this plant to the cows and continued to be excreted at a relatively constant level, after an induction period, for 62-70 h after the bracken diet had ceased. The average value of total ptaq excreted ([ptaq]e) from milk amounted to 8.60±1.16 % of the total ptaq ingested ([ptaq]i) during the entire feeding period. [ptaq]e was linearly dose dependent in the 2 400 to 10 000 mg/animal/d range of ptaq given to the test animals and the ratio [ptaq]e/[ptaq]i remained relatively constant at various ptaq dosages. In a two-pulse feeding sequence with a 72-h interlude when no bracken was given, a bimodal ptaq excretion curve was obtained. The implications to human health are discussed. © Inra/Elsevier, Paris.