Abnormal, defective offspring are a significant problem in livestock as well as in humans. Congenital malformations have been observed since ancient times and were once thought to be primarily of genetic origin. Knowledge relating to congenital anomalies has greatly increased in recent years. Numerous hazardous plants are abundant on many of the ranges grazed by livestock. Many of the plants, when ingested during certain stages of gestation, induce congenital defects. The defects can vary from minor changes to striking abnormalities. The final manifestations of abnormal intrauterine differentiation and development are death, resulting in reabsorption or abortion, malformation, suppression of growth, and disordered function. It appears that the type of malformation induced in a conceptus depends more upon the developmental stages in which the injurious agent operates than upon the type of the agent. The etiology and pathogenesis of congenital defects are complex. With time, and additional studies, other plants will probably prove to be teratogenic. Teratogenic studies and findings in animals have had beneficial influences for the livestock industry and for veterinary and human medicine.
