Effects of progesterone on developing chick embryos

Experiments were conducted to examine the effects of progesterone on the developing chick embryo with particular attention to the reproductive system. Differing levels of progesterone (0, .5, 1.0, or 2.0 mg) were dissolved in propylene glycol and injected at 4 days of incubation into the yolk sac of eggs from Barred Plymouth Rock females mated to New Hampshire males. Progesterone caused significant reductions in both weight and length and shank weight and length in 18-day-old embryos. Aside from reductions in embryonic growth, progesterone did not cause gross alterations in embryonic development. Progesterone modified neither normal morphology nor differentiation of male or female gonads and associated ductal systems.