Genetic Influences on the Behavior of Chickens Associated with Welfare and Productivity - Genetics and the Behavior of Domestic Animals - page 333

three-bird cages for over 20 weeks. That the housing environment can have a
significant effect on the duration of TI has been shown by Jones and Faure
(1981) , Kujiyat et al. (1983) , Campo et al. (2008) , and Lay et al. (2011) .
Escape and Avoidance (“Flighty”) Behavior
Consistent and significant differences in escape and avoidance behavior
of hens from two genetic stocks of White Leghorns were found for each of
three stimulus situations believed to cause fear ( Craig et al., 1983 ). Human
observers were involved in two of the tests and a mechanical device was the
primary source of stimulation in the third. In addition to stock differences,
significant sire family effects, indicative of genetic variation within strains,
were also found. Within genetic stocks, negative phenotypic correlations
were detected between criteria used as indicators of fearfulness and feather
loss; cages with more fearful hens lost more feathers presumably because of
abrasion with cages and trampling and scratching. Cages held from 10 to 14
birds each. In a later study, involving hens of a random-bred White Leghorn
stock kept in three-hen cages, Craig and Muir (1989) obtained heritability
estimates ranging from a nonsignificant value of 0.08 to a significant 0.34.
Potential Problems with Selection on Behavioral Traits
Wegner (1990) suggests that welfare could be improved through adaptation
by selecting against frustration, restlessness and stereotyped pacing before
laying, and a greater tendency to sit during the pre-laying period. However,
direct selection on either behavior or physiological objectives should be
viewed with caution. The intended results may not be as expected. For exam-
ple, Webster and Hurnik (1991) showed that traits associated with non-
aggression, such as sitting and resting, were negatively correlated with
productivity. Furthermore, the link between behavior and stress is misinter-
preted. For example, Duncan and Filshie (1979) showed that a flighty strain
of birds that exhibited avoidance and panic behavior following stimulation
returned to a normal heart-beat sooner than a line of more docile birds,
implying that docile birds may be too frightened to move. Therefore, is
flightiness good or bad for well-being?
An example of problems that can occur if selection is directed at the
physiological responses to stress was provided by Gross and Siegel (1985) .
They were successful in selecting lines of birds for high and low plasma cor-
ticosterone in response to social strife. Further testing ( Siegel, 1993 ) showed
that the birds did not differ in their corticosterone response to a non-social
stressor. Siegel concluded that genetic selection altered the perception of the
animal to stress rather than involving the GAS directly. Even worse, Siegel
(1993) noted that the low line in a low-strife environment was more suscepti-
ble to infections from endemic bacteria and external parasites while the high