EFFECTS OF UNDERNUTRITION AND OVERNUTRITION ON LACTATION IN LABORATORY RATS

To study the effects of maternal nutritional status on lactational per formance, the diets of laboratory rats were manipulated with food rest riction or increases in fat concentration, Compared with rats fed cont rol diets ad libitum, conception rate, milk production and lifter grow th decreased and milk fat concentration increased in both chronically food restricted and obese animals, Chronically food restricted rats mo bilized body fat and reduced their energy expenditure for maintenance and activity, Differences in suckling pattern between control and food -restricted rats affected hormone concentrations important for success ful lactation, Obese rats experienced greater difficulty than controls in delivering their pups and more of their pups died in the first day s of life, Milk production among obese rats may be constrained by poor appetite and the high heat production that characterizes lactation in litter-bearing species. There are many parallels as well as important differences between results obtained from these models and findings i n nursing women, Nevertheless, these models provide useful information about the possible mechanisms by which maternal nutritional status af fects lactational performance.