Investigation of the persistence of triclabendazole residues in bovine milk following lactating-cow and dry-cow treatments.

Triclabendazole is a flukicide used in the treatment of liver fluke in cattle. However, its use in the treatment of liver fluke is prohibited in dairy cows. In this work, two independent studies were designed to investigate the persistence of triclabendazole residues in milk following the administration of 10% Fasinex® as dry-cow and lactating-cow treatments. In the dry-cow study, 36 in-calf dairy cows were treated with a commercial product, 10% Fasinex®, at drying-off and three triclabendazole residues (triclabendazole, triclabendazole sulphoxide and triclabendazole sulphone) were monitored in the milk following calving, approximately 60 days post-treatment. No residues were measurable in the milk of the 36 cows tested – the LOQ of the method was 1.00 µg kg−1. In the lactating-cow study, the persistence of four triclabendazole residues was investigated in the milk of six dairy cows. The highest levels of triclabendazole, triclabendazole sulphoxide, triclabendazole sulphone and keto-triclabendazole residu...