Natural plant toxicants in milk: a review

Elimination of plant toxicants via milk by lactating animals is considered a minor route of excretion; however, it may be important when the health of the neonate or food safety in humans is considered. Among plant toxicants excreted in milk is tremetol or tremetone, the toxin in white snakeroot (Eupatorium rugosum) and rayless goldenrod (Haplopappus heterophyllus). These plants have been responsible for intoxication of cows and their suckling calves and for many human poisonings. Other plant toxins excreted through the milk that pose a toxicity hazard include pyrrolizidine alkaloids in Senecio, Crotalaria, Heliotropium, Echium, Amsinckia, Symphytum (comfrey), Cynoglossum (hounds tongue) and Festuca (tall fescue); piperidine alkaloids in Conium, tobacco and others; quinolizidine alkaloids in Lupinus; sesquiterpene lactones of bitterweed and rubber weed; and glucosinolates in Amoracia (horseradish), Brassica (cabbage, broccoli, etc.), Limnanthes (meadowfoam), Nasturtium (watercress), Raphanus (radish) and Thlaspi (stinkweed). Many plants such as Astragalus, Oonopsis, Stanleya, Xylorrhiza, Aster, Atriplex, Sideranthus and Machaeranthera accumulate selenium and may cause intoxication when grazed. Selenium is found in the milk at concentrations relative to the amounts ingested by the lactating animal. Excretion of selenium via the milk is important in the deficiency state, but when in excess it may cause toxicity to offspring.