To help identify determinants of rat appetitive behavior during the weanling period, rat pups 17-32 days of age were studied in a Y-maze. One arm of the maze provided pups with the opportunity to suckle a lactating or nonlactating anesthetized female. The other arm always contained a familiar food, either liquid diet or ground laboratory chow. In some experiments the dam was separated from the food compartment by a thin gauze screen. In other tests maternal contact could be maintained in the feeding goal but suckling in that compartment was prevented by nipple involution. Age was the major determinant of choice, with more older animals choosing the food arm. Availability of maternal contact in the feeding compartment increased the percentage of rats that chose to feed by about 20% at all ages studied. Food quality, but not quantity, affected choice at each age, as did lactational status. Prior food, water, and maternal deprivation (2 or 24 hr) did nof affect choice behavior at any age but did influence behavior in the goal box. These fiidings are discussed within the context of the changing demands faced by the rats during the weaning period.
Ingestive behavior in altricial mammals follows an ontogenetic course that traverses three successive stages. In the first stage all nutritional, hydrational, and mineral needs are satisfied exclusively through suckling. Then, at the onset of weaning, such needs are met by feeding and drinking in conjunction with suckling. In the third stage suckling yields to free feeding and drinking. Among albino rats (see Babicky, Ostadalova, Parizek, Kolar, & Bibr, 1970;Bolles & Woods, 1964;Redman & Sweney, 1976;Rosenblatt & Lehrman, 1963), the animal whose ingestive ontogeny has been most extensively studied in the laboratory, the initial stage lasts for about the first 2 weeks after birth, at which time free feeding and drinking first appear. Then, until about 28 days of age, suckling, feeding, and drinking coexist. Rats older than 28 days, studied under standard laboratory conditions, do not suckle. Weaning is considered complete.
Yet to define weaning simply as the initiation of feeding and cessation of suckling belies the complexity underlying the weaning process. This definition does not adequately capture the infant's changing perception of its mother as she becomes increasingly inaccessible. Furthermore, it does not consider the possibility that suckling, like other ingestive behaviors, may be influenced by the quality and quantity of the other choices available to the animal. Accordingly, by allowing pups to either suckle or feed in