Radiosensitive period of pecking response during embryological development of domestic chicks.

Abstract

Gamma irradiation of 174 chick embryos on days 2 to 12 of incubation in 2-day steps resulted in a fivefold increase in between-subjects variance and a threefold increase in withinsubjects variance when tested with induced pecking responses, but only in groups treated on days 6 and 8. There was no difference in variances between groups treated on any other day nor in the controls. It was claimed that comparison of means was an inappropriate and misleading test for treatment effects. Results were discussed in terms of both raised thresholds and loss of negative feedback in the response system. (auth)