No persistent effect of preweaning nutrition on postweaning food intake, feeding efficiency, or body energy stores in Long-Evans rats

Abstract

The purpose of this study was to determine the relative importance of pre- and postweaning nutrition on body mass, body fat, and feeding efficiency in Long-Evans rats up to a period of 18 weeks following weaning. Female rats were bred and pups were redistributed to form large (14–19 pups), normal (11–13 pups) and small (4 pups) litter groups. Weaned rats were housed as pairs (40 pairs) or singletons ( n = 16) and fed either a mixed-fat diet (36.6% fat) or a standard chow diet (13.5% fat). Food intake, body mass, and feeding efficiency were measured at 4, 8, 12, and 18 weeks postweaning. Total body fat and depot fat pad mass were also measured at 18 weeks postweaning. At weaning, pups from small litters were fatter ( p < 0.001), and had a greater mass ( p < 0.03) than pups from large litters. There were no persistent effects of preweaning litter size after covarying for preweaning mass on body mass, and postweaning growth, food intake, feeding efficiency, or body fat accretion. Male rats ingesting the mixed-fat diet had a greater body mass ( p < 0.05), greater body fat accretion ( p < 0.008) and a higher feeding efficiency ( p < 0.001) than their chow-fed counterparts, despite an overall lower energy intake ( p < 0.05). Female rats ingesting the mixed-fat diet had a lower food energy intake ( p < 0.005) and a greater feeding efficiency ( p < 0.001) than chow-fed rats during the early postweaning period, only. Thus, postweaning nutrition may play a more important role in postweaning adult mass and depot fat in freely eating rats than early nutritional experiences.