This article presents a brief overview of stress and its impact on growth, production, reproduction and disease susceptibility in farm animals. A single measure of stress might not be a reliable indicator and it is usually more informative to combine multiple indicators of stress to assess animal welfare. Popular measures of stress such as alterations in hormonal profiles can be complemented with behavioral and immunological changes. Traditional approaches are insufficient to unravel the role of large number of genes and interconnected genetic pathways leading to multiple responses to stresses. Modern genomic and proteomics methodologies used in identifying the biomarkers and molecular mechanisms of stress response have also been described briefly. With a better understanding of the basic biology, altered physiological processes and the genes/proteins involved in stress adaptability, it would be possible to develop methodologies for selection of animals with better performance and devise strategies for animal welfare.