Plants Associated with Congenital Defects and Reproductive Failure (3-Mar-2004)

Considerable livestock losses occur annually as the result of toxic plants that cause embryonic death, abortion, and fetal abnormalities [1-3]. Plant toxins also interfere with reproduction through their effects on male fertility, especially by affecting spermatogenesis. The plant species that have been historically associated with abortion and infertility in livestock are listed in Table 8-1. Those plant toxins capable of causing fetal death or deformity are referred to as teratogens. To be a teratogen, a plant toxin must readily cross the placenta at a high enough dose and be present at a specific time in gestation to exert its effect on the developing fetus [3,4]. In addition, susceptibility to a plant teratogen depends on the animal species, because not all species are equally susceptible to teratogens. In general, the fetus is most susceptible to teratogens during the first trimester of pregnancy. The western false hellebore (Veratrum californicum) is a classical example of a teratogen because it only induces the cyclops deformity in lambs if the pregnant ewe eats sufficient quantity of the plant during the 13 14th days of gestation [5]. Other than plant teratogens, viruses, nutritional imbalances and deficiencies, chemicals (nitrates), and radiation may also be teratogenic and must be considered when determining the cause of congenital deformities. The plants that have been confirmed or suspected of being teratogens in animals are listed in Table 8-2.