Dietary nutrients and contaminants in laboratory animal experimentation.

Analyses for selected components in random samples of natural product diets for experimental rodents revealed significant variations in content of nutrients and contaminants in various lots of feed. Modification of the diet and contamination with any of several toxicants appreciably affected the responses of experimental animals to specific drugs or chemicals under test, which could cause biased interpretation of results. Therefore, continuous monitoring of laboratory animals' diets and maintenance of quality control are necessary. For example, low magnesium concentrations may affect the kidney; excessive calcium concentration may influence absorption and utilization of zinc; excesses of vitamins A and D are highly toxic; deficiency or excess of selenium affects biological systems; and poor protein quality may provide inadequate or imbalanced amino acids and thereby influence structure and function of animal systems in experimental studies. Important contaminants are the mycotoxins (particularly aflatoxin), heavy metals (lead, mercury, cadmium, arsenic), nitrates and nitrosamine (N-dimethylnitrosamine), chlorinated hydrocarbons, and polychlorinated biphenyls.