Improving the Adaptability of Animals by Selection - Genetics and the Behavior of Domestic Animals - page 310

( Grignard, 1996 ). The archistriatum has undergone some form of change
during selection, and further research will attempt to determine the nature of
these changes.
Hoggs et al. (1994, 1996) showed that the forebrains of short TI line
(low fear) birds contain more benzodiazepine receptors than those of the
high TI (high fear) quail and that these receptors were more sensitive to
GABA stimulation in the long TI than in the short TI line. GABA is a neuro-
transmitter. The benzodiazepine receptors are the same receptor sites that are
bound by the tranquilizing drug valium (diazepam). These findings indicate
that selecting birds for either short or long toxic immobility affects both
the number and the affinity of neurotransmitter sites in the brain. The sites
affected by selection for either high or low fear are bound by both tranquiliz-
ing drugs and brain neurotransmitters that have a calming effect. These stud-
ies are evidence that selecting for fearful behavior affects neurotransmitters
which modulates fearfulness.
Jacquet and Launay (unpublished data) also demonstrated that there is
a tendency for certain plasma cathecolomines to be more abundant in the
brains of LSR line birds than in those of HSR line birds. However, none
of the differences reported were statistically significant. Isolation induced
similar increases in the plasma adrenaline level in both lines.
There has, therefore, been some effect of selection on brain metabolism
but again more work needs to be done before it will be possible to elucidate
the various mechanisms involved.
CONCLUSIONS
Selection for low fear and high social motivation seems likely to produce
animals that show better adaptation and have better welfare under intensive
husbandry conditions. Our experiments used Japanese quail; this species
appears to be a good model of the domestic chicken, and it is likely that sim-
ilar selection could be conducted in that species. Furthermore, fear and social
motivation are such basic motivational systems that with appropriate modifi-
cation of the methods used, similar selection techniques could be used in a
wide variety of domestic species.
Fear and social reinstatement behavior have general adaptive value. It is
unlikely that fear reactions can be completely eliminated from any environ-
ment; all environments involve social reactions through either social behav-
ior or social deprivation. The experiments described here show that selection
for or against fear and sociality is possible using simple short-term measures
and that the traits selected are not specific to a given age or environment.
The short tonic immobility line showed less fear and fewer fear-induced
stress responses than did long tonic immobility line chicks in most of the
situations investigated. They are therefore probably better adapted to inten-
sive rearing conditions and would be likely to maintain greater productivity