The preference-aversion behavior of rats for nutritionally-controlled diets containing oil or fat

The preference-aversion behavior of Sprague-Dawley rats for semi-purified diets containing various levels of either corn oil, animal fat (lard) or hydrogenated vegetable oil (Crisco) was determined in brief and long-term, two-choice preference tests. After the first day of exposure, rats selected more calories from the control-unadulterated diet than from experimental diets containing either oil or fat. Only in the first hour of exposure (with diets containing either 5% Crisco, 15 or 25% lard) or in the first day (with diets containing 5% Crisco, 5 or 15% lard) was a preference for experimental diets observed. There were significant effects of oil and fat concentration and of exposure time upon preference for experimental diets, such that preference for the experimental diets was reduced as levels of oil or fat and as the time of experiment increased. Changes in diet selection had no major effect on total caloric intake measured as the sum of both experimental and control dietary choices, although total intake on a daily basis tended to decrease during the middle portion (2-4 days) of the study, then recover by the end of the study. The results suggest that postingestional factors related to the dietary oil and fat (rather than the sensory properties of the diets) directed the long-term preference behavior of rats for semi-purified diets adulterated with various levels of either corn oil, animal fat (lard) or hydrogenated vegetable oil (Crisco).