Comparison of AIN-76A and AIN-93G diets: a 13-week study in rats

Either purified or cereal-based diets may be used for toxicity testing in rats. Purified diets have advantages in terms of flexibility of formulation to meet specific study objectives and also assurance of relatively low levels of contaminants (e.g. heavy metals and pesticides). The American Institute of Nutrition recommended that the widely used purified diet AIN-76A be replaced by two newer diets, AIN-93G (for use during rapid growth, pregnancy and lactation) and AIN-93M (maintenance diet). The present study compared AIN-76A and AIN-93G by feeding these diets for 13 weeks to male and female rats. A cereal-based diet was also included for reference purposes. The groups fed purified diets had higher serum cholesterol and triglyceride levels than the chow-fed group. An increased incidence and severity of renal tubular mineralization in the purified diet groups was not observed in this study (in contrast to other published studies where rats were fed AIN-76A). Several histopathologic observations, including eosinophilic gastritis and mucification of gastric glands of the glandular stomach, occurred at higher rates in the AIN-76A group than the other dietary treatments. Hepatocellular fatty changes occurred in the purified diet groups at a significantly higher rate than in the chow diet group. In conclusion, AIN-93G is an appropriate diet for use in rat safety evaluation studies.