Effects of early life undernutrition in artificially-reared rats: 3. Further studies of growth and behaviour

Abstract

Four groups of rat pups were reared: mother-reared control (well-fed) and undernourished (MRC, MRU) and artificially-reared control and undernourished (ARC, ARU). AR rats were fed expressed rats' milk (days 5–7), mixtures of rats' milk and milk substitute (days 8–16), and milk substitute only (days 17–20) by intermittent infusion via a gastric cannula. Undernutrition, imposed from 5–25 days, was effected initially by underfeeding the mother (MRU) or by infusing restricted quantities of milk (ARU). Weaning was at 21 days and undernutrition from 21–25 days was by restricting the supply of solid food. All rats were fed ad lib from 25 days. From 18 weeks, male rats were subjected to 3 tests of behaviour: spontaneous alternation, conditioned food preference, and visual discrimination (Lashley stand). There were negative effects of both undernutrition and artificial rearing on body growth in weight and length. For two aspects of behaviour, preference for carbohydrate relative to protein (greater in U rats) and latency to jump (longer in U rats) the effects of early undernutrition were the same in both MR and AR animals. Hence, these effects cannot have been mediated through alterations in maternal care.