Genetic Influences on the Behavior of Chickens Associated with Welfare and Productivity - Genetics and the Behavior of Domestic Animals - page 314

Chapter 9
Genetic Influences on the
Behavior of Chickens Associated
with Welfare and Productivity
William M. Muir * and Heng Wei Cheng †
*Purdue Agriculture, West Lafayette, IN, USA; † Purdue Agriculture, Livestock Behavior
Research Unit, USDA-ARS, West Lafayette, IN, USA
INTRODUCTION
Behavior is the observable actions, mannerisms, and means by which animals
cope with their environment, including other animals in that environment. The
environment may be considered in terms of both the internal or physiological
environment and the external environment. The latter may be subdivided,
with some overlapping, into social and physical aspects. When failure to cope
with changes is detected in chickens, the question arises as to whether there
should be an attempt to adapt the environment to the bird or the bird to the
environment ( Muir, 1996, 2003; Muir and Cheng, 2004 ). Similarly, Cheng
(2007) questions “Should we change housing to better accommodate the
animal or change the animal to accommodate the housing?” Attention in this
chapter is focused on genetic modification to improve the chickens to adapt-
ability to their environments and consequently to enhance their welfare.
In the last half of the 20th Century the greatest change in the layer industry
was that from floor pens to batteries of multiple-hen cages. The popularity of
multiple-hen cages resulted in part because commercial producers found that
multiple-hen cages offered several advantages in both economic and animal
welfare aspects, including higher feed efficiencies ( Cunningham, 1992 ),
improvement of biosecurity and food safety ( De Vylder et al., 2011; Hannah
et al., 2011; Holt et al., 2011; Jansson et al., 2010; Jones et al., 2011 ), and
reduced housing and labor costs ( Craig, 1982; de Boer and Cornelissen, 2002;
Sumner et al., 2011; Van Horne, 1996 ). Ironically, the biggest change in the
21st century may be away from cages and a return to floor pens or alternative
rearing systems ( California proposition 2, 2008; United Egg Producers, 2011 ).
Craig and Swanson (1994) , Goodwin (2001) , Mellor and Stafford (2001) ,
Hemsworth (2007) , Swanson (2008) ,and Mench et al.(2011) examined both
historical and current ethical perspectives and attitudes towards husbandry