Biology of the rice rat (Oryzomys palustris natator) in a laboratory environment. VII. Pre-weaning growth of the body.

Body growth using weight and length parameters have been examined following the introduction of the rice rat to laboratory conditions and a history of breeding covering some 15 generations. The pattern of growth shows a characteristic enphasic form which appears to be determined by the interplay of the external environment and the genetic endowment. The external environmental factors include the waxing and waning of the lactational performance of the mother and the intake of solid food, resulting in the first phase being mainly controlled by the maternal environment, the second phase being mainly controlled by a lessening maternal environment + external (solid food) environment + some genetics, the third phase being influenced by external environment + genetic endowment.