Size and Rate of Involution of the Hen’s Reproductive Organs

IN BIRDS, a cycle of development and involution of the reproductive organs generally accompanies the mating season. These changes are associated with a renewal of the plumage (i.e., a molt), but the causal relationships between these processes are not certain (Greenwood, 1936). These natural changes in the reproductive organs have been largely eliminated in the domestic chicken, with eggs being produced more or less regularly throughout the year. The hen, however, retains the capacity for involution and regeneration of its reproductive organs, and this sequence may be induced in a number of ways: by withholding feed and water or by excluding light (Hall, 1946), by thyroid administration (Van der Meulen, 1939), by progesterone administration (Adams, 1955; Shaffner, 1955), or by Enheptin feeding (Pino, 1955). The rate of development of the fowl’s reproductive organs with the onset of sexual maturity has been described (Hafez and Kamar, 1955). The size of the …