A comparison of the effects of slow release, injectable levonorgestrel and depot medroxyprogesterone acetate on egg production in Japanese quail (Coturnix coturnix japonica)

The effects of levonorgestrel and medroxyprogesterone acetate on egg production were studied in Japanese quail. Birds were divided into three groups and injected with a depot form of levonorgestrel, a commercially available formulation of medroxyprogesterone acetate, or a saline control. Daily egg production, daily fecal estrogen concentration, and weekly body weights were monitored 7 days before and 70 days after drug or saline administration. The birds were euthanatized 70 days after treatment. A complete necropsy was done on each bird, and selected tissues were examined histologically. All birds treated with levonorgestrel ceased egg laying by the second day after injection, and the average duration of cessation of egg laying was 67.1 +/- 4.06 days. In five of seven birds treated with medroxyprogesterone, the average duration of cessation of egg laying was 5.8 +/- 2.3 days. In the remaining two birds, egg laying stopped for an extended time (19 and 49 days). The control birds continued to lay throughout the study. Fecal estrone conjugate profiles for quail treated with levonorgestrel and medroxyprogesterone varied compared with the control birds. Concentrations of fecal estrone conjugate decreased between days 1 and 40 in birds treated with levonorgestrel, varied for the duration of the study in birds heated with medroxyprogesterone, and did not fluctuate in the control birds. Necropsy findings in birds treated with levonorgestrel revealed a retained egg within the oviduct of three birds and a calcified egg within the coelomic cavity of one bird. Results of histologic examination were unremarkable in all birds. These results show that a single dose of repository levonorgestrel is effective in preventing egg laying in healthy, young adult Japanese quail.