INDIVIDUAL-DIFFERENCES IN THE MACRONUTRIENT PREFERENCE PROFILE OF OUTBRED RATS - IMPLICATIONS FOR NUTRITIONAL, METABOLIC, AND PHARMACOLOGICAL STUDIES

While screening outbred male Holtzman Sprague-Dawley rats for their ma cronutrient (protein, carbohydrate, and fat) preferences, we noticed s ubstantial group-to-group variation in the preference profile. This le d us to analyze preference data on two hundred and seventy rats collec ted over a three-year period to determine whether preferences could be predicted. The results led us to conclude that observed variations in macronutrient preference profiles may be secondary to genetic heterog eneity in the outbred population. We have also shown that the outcome of the pharmacologic effects of two agents (insulin and enterostatin) on appetitive behavior will vary from animal to animal within a single group. Accordingly, researchers must be aware that the breeding histo ry of the laboratory animal is a major factor in the outcome of the ex periment and interpretation of the findings.