Genetic Influences on the Behavior of Chickens Associated with Welfare and Productivity - Genetics and the Behavior of Domestic Animals - page 319

sensitive indicator of well-being ( Adams and Craig, 1985; Appleby and
Hughes, 1991, pp. 116

117; Cunningham et al., 1988 ). Productivity indica-
tors may be useful measures of the continuing effects of stressors when hens
have made an adjustment to the “stage of resistance” as defined by physio-
logical criteria. For example, Beuving and Vonder (1978) reported and
reviewed by Ruszler (1998) : little or no behavior evidence of the stressful
conditions of high temperature or water and feed deprivation after the first
few days, though their hens stopped laying.
The relationship between stress and production also supports the notion
that production is a good indicator of stress. Siegel (1995) and Scheele
(1997) pointed out that stress has important consequences on the birds' well-
being, especially those that affect energy and mineral metabolism and
interactions with the immune system. Social or behavioral environments
can also activate stress responses in birds just as physical stressors do
( Cheng et al., 2002, 2003 ). Results may manifest themselves in reduced
growth in juveniles, reproductive capacity in adults and increased food
consumption.
When management of broiler breeder stock is considered, a problem with
interpretation of their welfare arises. Because of excessive appetites, birds to
be kept as broiler breeders are severely restricted in feed intake. This prac-
tice prevents obesity of adults which if uncontrolled reduces health, longev-
ity, and reproductive performance, and increases the incidence of leg
problems ( de Jong et al., 2005; Hocking et al., 2004; Siegel, 1984; Tolkamp
et al., 2005 ). By the criteria cited above, productivity indicates improved
well-being with broiler breeders on feed restriction. Nevertheless, feed depri-
vation has been shown to cause increased aggressive pecking of chickens
( Duncan and Wood-Gush, 1971; King, 1965; Mench et al., 1986; Shea et al.,
1990 ). Nevertheless, from the standpoint of physiological indicators, it
appears that broiler breeders on feed restriction adjust rapidly ( Benyi et al.,
2009; Katanbaf et al., 1989 ).

Behavior
European researchers often use behavioral criteria as the primary, or some-
times the only, indicator of hens' welfare ( Baxter, 1994; Faure and Mills,
1989; Savory and Hughes, 2010; Sorensen, 1981; Wegner, 1985 ). Dawkins
(1983) was critical of such an approach and wrote:
At first sight, the growing awareness that an animal's behavior may be
important evidence to have when assessing its welfare is entirely to be wel-
comed. But there is, amid the encouraging trend of a greater use of ethological
data, also a disturbing one of possible misuse of ethology.
For example, Dawkins (1988) considered the absence of behavior patterns
seen in the wild as an invalid criterion of animal suffering although such
evidence is frequently used by critics of high-density cage environments.