Genes associated with functional traits in poultry: implications for sustainable genetic improvement Samuel E. Aggrey, University of Georgia, USA; Fernando González-Cerón, Chapingo Autonomous University, Mexico; and Romdhane Rekaya, University of Georgia, USA

Poultry production primarily focuses on the supply of saleable products, for example, meat and eggs since they are the primary sources of income for most poultry producers. As such, meat and eggs are classified as production traits, and have been the focus of improvement in poultry breeding organizations. Genetic improvements in production traits over the last six decades have been very successful and have led to a significant increase in productivity (Havenstein et al., 2003). Chick survival is essential to productivity and necessitates the normal functioning of basic biological mechanisms under reasonable environmental conditions. Functional traits of birds have not received much attention compared to production traits due to several reasons, including (1) availability, expense and practicality of direct measurements; (2) accuracy of indirect measurements; (3) low heritability and accuracy of genetic parameters; and (4) negatively correlated with production traits. Functional traits may be defined as the morphological, biochemical, physiological, immunological and behavioural attributes that are considered to be essential

for the optimal functioning of the individual and also the response of such individuals to the environment. Functional traits are therefore at the crossroad between responses to production traits and the environment. A suboptimal production environment directly limits the expression of functional traits and indirectly affects production responses. Conversely, genetic improvements in production traits could adversely affect functional traits and limit a bird’s ability to thrive optimally in the production environment.