Nutritional adequacy and quality control of rodent diets.
One of the most often neglected variables in experimental investigations using rodents is the diet. Recent observations that diets can influence the response of a rodent to the drug, chemical or other factors under study, with biased interpretation of results, have drawn great interest. In order to be assured that the biologic response observed is a reflection of the material or condition under study, it is imperative that the diet provide essential nutrients in the proper proportions and that contaminants be kept to a minimum. Quality control is the key to these requirements; rodent diets can provide adequate nutrition, free of significant contamination. The diets which can be provided vary according to the degree of refinements; the three major types are (1) natural product, (2) semipurified and (3) chemically defined diets. Natural product diets may be open or closed formula, depending on the amount of information that the label reveals. Guaranteed analyses of proximate nutrients are provided but are of little use in assessing the nutrient value of the formulation. The National Academy of Sciences, National Research Council publications on laboratory animal nutrient requirements should be available to all investigators using experimental animals to help them evaluate the nutritional adequacy of the diets they use. Rats and mice may be considered together under some circumstances relative to crude dietary needs, but the Syrian golden hamster should be treated separately for purposes of diet. This species appears to digest foods more like a ruminant. An ideal diet for rodents is not on the horizon because of variable needs relative to different types of research and holding. Storage and shelf life of rodent diets also play important roles in providing adequate nutrition. Variations in moisture, temperature and exposure to other chemicals can affect the quality of the feed and research results. In addition, a number of chemical and biological contaminants have been found in rodent diets, and surveillance over such variables must be a part of all laboratory animal diet quality control. Federal regulatory mandates now require that investigators assure that nutrient requirements of animals are met and that diets are reasonably free from contamination. Accepted practices in good management, formulation, shipping and storage will help achieve these commendable goals.