Toxicity and reproductive effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in ring-necked pheasant hens

Hen pheasants (Phasianus colchicus) injected with graded single doses of TCDD (6.25, 25, or 100 micrograms/kg) exhibited delayed-onset body weight loss and mortality--classic signs of the wasting syndrome. The lowest single dose of TCDD to produce this effect was 25 micrograms/kg. When hen pheasants were treated weekly with far lower doses of TCDD (0.01-1.0 microgram/kg/wk) for 10 wk, signs of the wasting syndrome and mortality were also produced. The lowest cumulative TCDD dose required to produce the response, using a weekly dosing regimen, was 10 micrograms/kg. Furthermore, using this dosing regimen, egg production by hens treated with a cumulative TCDD dose of 10 micrograms/kg was reduced, as was hatchability of their eggs. We conclude that hen pheasants are responsive to the overt toxic effects of TCDD and that the lowest cumulative dose of TCDD that produces overt signs of toxicity, 10 micrograms/kg, also reduces egg production and egg hatchability.