Dietary self-selection in cycling and neonatally ovariectomized rats

Abstract

Dietary self-selection patterns were assessed in normally cycling (four-day estrous cycle) rats with separate provisions of fat (olive oil), carbohydrate (sucrose), and protein (casein). There was no fluctuation in daily caloric intake across the estrous cycle, but animals did demonstrate changes in consumption of specific macronutrients during the 24-h period in which estrus occurred. At estrus, animals exhibited increased carbohydrate intake and decreased fat intake in comparison with the remaining three days of the cycle. There was also a somewhat decreased (non-significant) protein consumption at estrus. Rats that had been ovariectomized on day 5 postnatally and then tested as adults in our paradigm ingested approximately the same quantity of daily kilocalories as observed in intact animals; but ovariectomy produced changes in consumption of specific macronutrients. In comparison with the intact animals, ovariectomized animals displayed increased fat intake and decreased carbohydrate intake. Thus, the fat and carbohydrate self-selection patterns of our ovariectomized rats reflected the elimination of estrus behavior.