Strychnine alkaloid and avian reproduction: effects occur at lower dietary concentrations with mallard ducks than with bobwhite quail.

Separate subchronic reproductive toxicity studies were conducted using mallard ducks (Anas platyrhynchos) and northern bobwhite quail (Colinus virginianus). Three groups (32/group; 16 male-female pairs) of 17-week-old ducks (F0 generation) were fed Purina Game Bird Breeder Layena diets containing mean (+/-SD) 33.2 (+/-2.7), 68.9 (+/-1.8), and 140.9 (+/-5.1) microg/g strychnine for 20 weeks, with some pairs in each group fed control diet during a subsequent 3-week recovery period. Three groups (32/group; 16 male-female pairs) of 19-week-old quail (F0 generation) were fed similar diets containing mean (+/-SD) 279.2 (+/-10.1), 557.4 (+/-43.5), and 1,113.6 (+/-46.6) microg/g strychnine for 22 weeks without a recovery period. Separate groups of ducks and quail (32/group; 16 male-female pairs) were also fed control diets (0.0 microg/g strychnine) in each study. There were 16 weekly collections of eggs for the mallard study (13 for the diet-exposure period and 3 for the recovery period), and 11 collections for the quail study. Eggs laid during the last 13 and 10 weeks of the diet-exposure periods for ducks (plus 3 weeks of the recovery period) and quail, respectively, were incubated. Each hatch of F1 generation ducklings and chicks was observed for 14 days. Key results were: (1) the no observed adverse effect levels (NOAELs) for F0 ducks and quail were 33.2 and 1,113.6 microg/g strychnine, respectively--quail showed no reproductive effects at the current doses; (2) decreased egg production and hatching success occurred for mallard hens fed mean 140.9 microg/g strychnine diets; and (3) "normal-hatching" ducklings from eggs of F0 mallards fed mean 140.9 microg/g strychnine diets suffered greater mortality than ducklings from the other diet groups. Possible mechanisms of strychnine action on avian reproduction are discussed.