Effect of embryonic treatment with oestradiol benzoate on reproductive morphology, ovulation and oviposition and plasma LH concentrations in female quail (Coturnix coturnix japonica).

Quail eggs were injected on Day 10 of incubation with 0, 5, 10, 20 or 40 micrograms oestradiol benzoate. Females hatching from these eggs were reared on a 16L: 8D photoperiod and egg laying was recorded. Blood samples were taken at 37, 40, 43, 46, 49, 52, 55, 58 or 61 days of age and LH concentrations were measured by a double-antibody radioimmunoassay. Birds were killed at 61 days of age; ovaries and oviducts were weighed and examined. Egg laying was greatly reduced by oestradiol benzoate treatment, but for birds that did lay, age at first oviposition was normal. LH levels were not affected by oestradiol benzoate treatment, and were highest at 40 and 49 days of age. Oestradiol benzoate had no effect on ovarian weight, number of follicles with diameter greater than 1 cm, or number of post-ovulatory follicles. Oestradiol benzoate had a dose-related effect on the likelihood that females would have two oviducts, and for those females that had retained the right oviduct, the left oviduct was smaller than normal. Oestradiol benzoate-treated females were more likely to have ovulated yolks in the body cavity. Embryonic treatment with oestradiol benzoate therefore appears to inhibit egg laying by causing oviduct abnormalities, rather than by (as happens in mammals) inhibiting ovulation.