EFFECTS OF AN IN OVO INJECTION OF AN ANTIANDROGEN ON EMBRYONIC AND POSTHATCHING GROWTH OF BROILER CHICKS

Experiments were conducted to determine whether in ovo injection of Fl utamide(R), a nonsteroidal anti-androgen, would affect posthatching gr owth of broiler chickens. Before doing these studies it was necessary to develop a bioassay to demonstrate that Flutamide(R) had anti-androg enic actions when injected in ovo. In ovo injection of 0.06 to 1.74 mu mol of testosterone propionate (TP) per egg on the 8th d of incubatio n caused a dose-related decrease in weight of the bursa of Fabricius o f newly hatched chicks. In subsequent experiments, 1.74 mu mol of Flut amide(R) significantly decreased the bursal regression produced by 0.5 8 mu mol of TP when both substances were injected on Day 8 of incubati on and bursal weights were taken on the day of hatch. Having establish ed that Flutamide(R) could block the effects of high doses of exogenou s TP, it was reasoned that it could block the action of much lower end ogenous levels. In two of the three experiments, injection of Flutamid e(R) 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 suppre sses the posthatching growth of male broilers.