The response of the oviduct to exogenous hormones in ovariectomized canaries in winter was compared with the development of the oviduct of intact birds during the natural breeding season. In contrast to other studies, in which only oviduct weight was measured, a number of parameters and the relationships between parameters were assessed: oviduct weight, diameter of the magnum region of the oviduct, the height of the mucosal folds of the magnum and the development and secretory activity of the tubular glands of the magnum.
Oestrogen had a dose dependent effect on oviduct weight. Simultaneous administration of progesterone or prolactin with the oestrogen did not significantly increase oviduct weight, but testosterone did. However, an increase in oviduct weight produced by hormone treatment may involve development abnormal in other respects.
The relationships between weight, diameter and glandular development were more disrupted at low dose levels of oestrogen than at higher doses. Combinations of oestrogen (0-05 mg) with progesterone (2-0 mg) or with testosterone (0-25 mg) produced oviducts more similar in weight/diameter relationship to normal breeding birds than did oestrogen alone, indicating that synergy may occur even early on in oviduct development. The role of hormones during the natural breeding season is discussed but it is not yet possible to ascribe particular roles to progesterone or testosterone. Exogenous prolactin had only a small effect but its role in the intact bird cannot be ruled out.