Transfer of tropane alkaloids from maize silage contaminated with Datura stramonium to milk of dairy cows

Datura stramonium, a poisonous plant producing toxic tropane alkaloids (L-hyoscyamine and scopolamine), is increasingly spreading on agricultural crop land used for feed production. To examine the transfer of tropane alkaloids (TAs) from feed to milk, four high yielding dairy cows received a total mixed ration containing maize silage naturally contaminated with Datura stramonium for ten days with a daily mean TA dosage of 0.12 mg/kg body weight. TA content of individual cow composite milk was measured at each milking using liquid chromatography-mass spectrometry. L-hyoscyamine was detected in milk with a mean of 0.90 µg/kg, corresponding to a steady-state transfer rate of 0.039% ±0.007%. D-hyoscyamine was detected in neither silage nor in milk, indicating no evidence for natural racemisation. Scopolamine remained below the limit of detection in milk. Health parameters of the experimental cows were monitored by clinical investigation and using a digital sensor system monitoring rumination. No clinical signs of intoxication were observed. Feed naturally contaminated with Datura stramonium can lead to TA occurrence in milk, which may contribute to consumer exposure. In the contaminated maize silage, Datura seeds and remaining plant parts were analysed separately to determine their contribution to total TA content. Total TAs in maize silage originated mainly from the Datura plant parts. Therefore, maximum levels based on the total TA content of animal feed instead of Datura seed weight may be more appropriate to protect animal and human health alike.