Plasma Calcitonin Levels in Birds During the Ovulation Cycle

High levels of plasma calcitonin (CT) have been detected in birds and other lower vertebrates (Kenny, 1971; Kenny, Boelkins, Dacke, Fleming & Hanson, 1972), but its role in these species remains unexplained (Kenny, 1972). In Japanese quail, plasma CT levels are higher in mature males than in egg-laying females (Boelkins & Kenny, 1970). It is possible that the level of plasma CT in females may vary during the ovulation cycle. We are investigating these levels with a view to elucidating the role of CT in the egg-shell calcification cycle of the laying bird; this report describes the preliminary findings. Mature egg-laying Japanese quail (Coturnix coturnix japonica) (aged 3–5 months) and chickens (Gallus domesticus) (aged 12–15 months) were maintained on a 10 h dark: 14 h light cycle (05.00 h on; 19.00 h off). Commercial laying diets were fed and drinking water was allowed ad libitum. Blood samples were taken quickly