Acta Vet. Brno 2007, 76: 325-331
Effect of Increasing Yolk Testosterone Levels on Early Behaviour in Japanese Quail Hatchlings
The aim of our study was to investigate effects of increased testosterone content in egg yolk on early behaviour of 1- and 2-day-old Japanese quail. 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 μl 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 inhibition of behavioural responses in hatchlings. Birds treated with testosterone in ovo displayed longer latency to leave the start square, decreased locomotor activity, enhanced defecation and lower number of distress calls as compared to control birds. In TI test, the influence of treatment 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. The effect is specific for a short period after hatching since previous studies reported stimulatory effect of yolk testosterone on behaviour of Japanese quail later in ontogeny.
Keywords
Maternal hormones, testosterone, quail, behaviour, ontogeny.
