Effect of increasing yolk testosterone levels on early behaviour in Japanese quail hatchlings
2007
Okuliarova, M.,Univerzita Komenskeho, Bratislava (Slovak Republic). Katedra Zivocisnej Fyziologie a Etologie | Skrobanek, P.,Slovenska Akademia Vied, Bratislava (Slovak Republic). Ustav Biochemie a Genetiky Zivocichov | Zeman, M.,Univerzita Komenskeho, Bratislava (Slovak Republic). Katedra Zivocisnej Fyziologie a Etologie
The aim of our study was to investigate the effects of increased testosterone content in egg yolk on early behaviour of 1- and 2-day-old Japanese quails. Three different doses of testosterone (0.25; 2.5 and 25 ng), not exceeding a physiological range, were examined in three separate experiments. Testosterone propionate dissolved in 20 microL olive oil was injected into the yolk before the onset of incubation. Behaviour of newly hatched chicks was recorded in response to both a novel environment in the open-field test and manual restraining in the test of tonic immobility (TI). Behavioural consequences of embryonic exposure to elevated testosterone were observed in the open-field test in all three experiments, which indicated the inhibition of behavioural responses in hatchlings. Birds treated with testosterone displayed a longer latency to leave the start square, decreased locomotor activity, enhanced defecation and lower number of distress calls than control birds. In the TI test, testosterone influence was manifested at the highest concentration only. Hatchlings from testosterone treated eggs expressed longer duration of TI and required less attempts to induce TI in comparison with the control group. Our results demonstrated increased fearfulness of Japanese quail chicks hatched from eggs with experimentally elevated testosterone content.
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