Master of Science (MS)
Animal Science (Animal, Dairy, and Poultry Sciences)
Increased fearfulness has been associated with adrenocortical activation. Maternal corticosterone (B) treatment increases egg yolk B, and elevated B in ovo enhances chick avoidance of humans. Quail selected for exaggerated (high stress, HS) as opposed to reduced (low stress, LS) plasma B response to stress are more fearful, and more B is found in the egg yolks of HS than LS hens. Therefore, the underlying fearfulness (tonic immobility, TI) and timidity (hole-in-the-wall box, HWB, emergence) responses were assessed in chicks hatched from eggs of LS and HS hens implanted with silastic tubes containing no B (CON) or B (B-IMPLANT) during egg formation. In chicks 14-15 d of age, the number of inductions (INDS) required to attain TI, the latency to first alert head movement (LATHEAD), and duration of TI were determined. In chicks 21-23 d of age, the latency until first vocalization (LATVOC), numbers of vocalizations (VOCS), proportions of chicks vocalizing (PVOCS), and the latencies to head (HE) and full body (FE) emergence from a HWB were determined. LS chicks required a lower number of INDS (P < 0.0005) and less time to achieve LATHEAD (P < 0.02) than did HS ones, although stress line, maternal B-treatment, and their interaction did not affect the duration of TI. During the acclimation period of the HWB tests, more (PVOCS; P < 0.0001) HS chicks vocalized sooner (LATVOC; P < 0.0001) and more often (VOCS; P < 0.0001) than did LS chicks; and, while maternal implant treatment did not affect LATVOC, progeny of B-implanted hens showed a tendency towards less (P < 0.07) VOCS than the CONs. A line*implantation treatment interaction (P < 0.02) was also found for VOCS. Post-hoc analyses of the interactive VOCS means showed that the HS-CON chicks vocalized more (P < 0.01) than the other three similarly less vocal groups. Chicks hatched from eggs of B-IMPLANT mothers also took longer to achieve both HE (P < 0.06) and FE (P < 0.05) from the HWB than did their CON counterparts. Stress line, implantation treatment and their interaction did not alter HE or FE responses. It was concluded that quail stress line genome may be affecting certain fear and alarm responses in chicks via the same or a different mechanism(s) that underlie(s) how maternal B increases in ovo B that in turn alters the fear behavior of progeny.
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Davis, Kyndal A., "Maternal corticosterone influences on fear responses in offspring of quail divergent stress response lines" (2008). LSU Master's Theses. 1322.
Daniel G. Satterlee