Concept of robustness
The concept of robustness in farm animals was defined by Knap (2005) as ‘the ability to combine a high production potential with resilience to stressors, allowing for unproblematic expression of a high production potential in a wide variety of environmental conditions’. Indeed, genetic progress in production traits realized at the nucleus level may become constrained in commercial practice if the resulting animals (end products of the breeding system) are raised in conditions that do not support full expression of their genetic potential. Robustness may then be seen as a global measure – as evaluated, for instance, by the realized level or functional longevity – of the sensitivity of the animal to the climatic, physical, nutritious, infectious and social environment, and to the metabolic load of its genetic potential for production traits. This concept also includes traits that are specifically sensitive to inadequate environmental conditions, such as skeletal and cardiovascular integrity, disease resistance and mortality in various stages, altogether known as ‘functional traits’. Such traits are important not only in terms of performance levels but also for animal health and welfare (Knap, 2009).