Suckling in rats extended by continuous living with dams and their preweanling litters

Abstract

To evaluate the role of the dam and littermates in weaning, rats were separated from their biological mothers, beginning at 21 days of age, and housed with a succession of dams and their 16–21-day-old litters. Suckling persistence was evaluated every 5 days until rats reached 70 days of age or no longer suckled. Rats housed in such a preweaning environment continued to suckle well past the normal age of weaning. Specifically, 50% suckled until day 55, and 15% suckled until they were 70 days of age and sexually active. In addition, the interactions among three dams and their litters composed of 16–21-day-old pups and a 45–50-day-old rat that had been housed with similar litters were analysed from time-lapse video-recordings. Experimental rats routinely suckled in the nest and withdrew milk from the dam, but did so only when most of the younger pups had already attached. These data suggest that the maternal and social milieu plays a role in the maintenance of suckling behaviour.