A Comprehensive Description of Intake of Diverse Foods By Rats (Rattus norvegicus) Selectively Bred on a Taste Phenotype

Eating is a central feature of the lives of opportunistic omnivores such as humans and Norway rats. Yet in most laboratory research with Rattus norvegicus, the food landscape is monotonous, and the studies utilizing a variety of foods shed little light on intake of individual foods or choice behavior. The present study provides the most comprehensive description to date of female and male laboratory rats’ intake of foods that they and humans encounter outside of the laboratory. In eleven experiments, test foods included varieties of peanut butter, cheese, cookies, meat, chocolate, fruits, and vegetables. Rats were given commercial products or custom versions that controlled for proportion of calories from fat and caloric density, one or two foods at a time. A final experiment examined pure macronutrient self-selection. Intraspecies diversity was modeled with rat lines selectively bred on a taste phenotype. All groups voluntarily ate every food, with intake (in grams) highest for vegetables and lowest for pure macronutrients. When Low- (LoS) and High-Saccharin-Consuming (HiS) rats differed, LoS rats ate more meat and fat and were choosier whereas HiS rats ate high-carbohydrate foods more avidly; exceptions and sex-dependent differences occurred. Using these results to enrich the food landscape for laboratory rats can enhance the comparative study of food intake and its relation to other behavioral systems.