Published online by Cambridge University Press: 20 November 2017
Genetic variation in physiological regulation has been studied in humans to explain disposition to hereditary metabolic diseases, such as diabetes, dwarfism and acromegaly. In farm animals the aim of such studies has more often focused on understanding individual variation with a view to develop physiologically based indicator traits that could help speed up genetic improvement programmes. To be efficient, any indicator trait needs to be measurable both early in life and in animals of both sexes. The advent of molecular or DNA based genetic markers has presented us with an alternative set of indicator traits. These may be seen both as competitive traits and as traits, which can be used in combination with physiological indicators.