Postnatal growth and organ development in Japanese quail selected for high growth rate.

As a result of selection for high growth rate in the quail the organ growth pattern has changed considerably. The main change, which characterizes the early part of the postnatal growth, consists of an increased relative size of the digestive organs and a lowered early growth rate of pectoral muscles and feathers. Since the increase in growth rate is linked to an increase in the relative size of the digestive organs, the growth rate is most likely restricted by the capacity to ingest and digest food. It also appears that at least part of the increase in growth rate is made possible by the change in organ growth pattern.