Date of this Version
Veterinary Clinics of North America: Food Animal Practice, Volume 27, Issue 2, July 2011, pp 429-446; doi:10.1016/j.cvfa.2011.02.010
The influence of natural toxicants and anthropogenic compounds on reproduction in food animals is significant in its economic impact, and the subject requires more research and further experimental substantiation. Confounding factors such as stress, nutritional status, season of the year, animal species involved, genetic variability, disease conditions, management factors, and so forth exacerbate the difficulty of making an accurate diagnosis and thereby may impede progress to improve reproductive performance on an individual operation. The interaction between the reproductive system and xenobiotics (reproductive toxicology) is a relatively new area of study and a subject of increasing interest, especially in the area of environmental exposures and potential work place toxicants affecting human health and reproduction.1 Much of the experimental literature about this subject comes from rodent models designed to replicate human exposure; however, the extrapolation to food-producing animals is limited at best. The list of compounds in this article with known effects on reproductive function is extensive and represents most classes of chemicals in the environment; however, this list is not intended to be exhaustive.
Investigation of reproductive dysfunction, especially infertility, abortions, and teratogenesis, should center on a thorough examination of animal condition and health, management practices, and infectious agents while potential toxicants are sought. This method requires a systematic approach including individual animal and herd/ flock history, veterinary examination of individual animals, testing of blood, urine, feces, or tissues, gross and pathologic/histologic postmortem examination, and toxicologic screening of samples of feed and or tissue. In livestock production systems, these investigations are often limited by economics, and the extent of the battery of tests must be determined in consultation between the animal producer, veterinarian, and diagnostician. Reproductive dysfunction includes all facets of reproduction, and when such dysfunction occurs failure to conceive, abortion, stillbirths, and anomalous fetuses may result.
Although the following discussion focuses on abnormal embryonic and fetal development (teratogenesis), many of the principles and methods outlined in this article may be used to investigate the other causes of reproductive dysfunction.