Improving the Adaptability of Animals by Selection - Genetics and the Behavior of Domestic Animals - page 296

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Generation

FIGURE 8.8 Number of inductions required to induce tonic immobility in lines of Japanese
quail selected for long or short duration of tonic immobility over 20 generations. ( & ) LTI,
( e ) CTI, ( x ) STI.

60

40

20

0

Generation

FIGURE 8.9 Distance run on the treadmill in lines of Japanese quail selected for long or short
duration of tonic immobility over 20 generations. ( & ) LTI, ( e ) CTI, ( x ) STI.

overlap. This implies that the long tonic immobility (LTI) and the short tonic
immobility (STI) lines had also become distinct genetic lines.
After 20 generations of selection, the number of inductions necessary to
obtain tonic immobility increased in the short TI line (3.88

1.47), remained

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relatively constant in the control TI line (1.47 6 0.75), and decreased in the

long TI line (1.04 0.20) ( Figure 8.8 ).

The distance run to reinstate social contact by the different TI lines
remained relatively constant and similar in all three lines up to the eighth
generation. Thereafter, distance run started to decrease in the long TI line
( Figure 8.9 ). This finding is not surprising as Jones et al. (1991) showed that
long tonic immobility chicks (high fear) have reduced activity levels when

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