Effects of an in ovo injection of an anti-androgen on embryonic and posthatching growth of broiler chicks.

Experiments were conducted to determine whether in ovo injection of Flutamide, a non-steroidal anti-androgen, would affect posthatching growth of broiler chickens. Before doing these studies it was necessary to develop a bioassay to demonstrate that Flutamide had anti-androgenic actions when injected in ovo. In ovo injection of 0.06 to 1.74 mumol of testosterone propionate (TP) per egg on the 8th d of incubation caused a dose-related decrease in weight of the bursa of Fabricius of newly hatched chicks. In subsequent experiments, 1.74 mumol of Flutamide significantly decreased the bursal regression produced by 0.58 mumol of TP when both substances were injected on Day 8 of incubation and bursal weights were taken on the day of hatch. Having established that Flutamide could block the effects of high doses of exogenous TP, it was reasoned that it could block the action of much lower endogenous levels. In two of the three experiments, injection of Flutamide on the 8th d of incubation resulted in a dose-related decrease in 21- and 49-d BW of male broiler chickens. The material had no effect on BW of males in one experiment and had no effect on BW of females at any age in any of the experiments. The data suggest that interference with the actions of endogenous androgens during embryonic life suppresses the posthatching growth of male broilers.