Behavioural changes as a correlated response to selection.

Abstract

Lines of mice have been selected for up to 50 generations on the following traits: high body weight, low body weight, high fat content or low fat content. The lines selected for high or low body weight differ by a factor of 2.5 and those selected for high or low fat content differ by a factor of five, both traits measured in 10 week old males. A set of behavioural traits was measured to ascertain whether this selection had caused correlated responses in behaviour: studies included feeding behaviour, open field behaviour, ultrasound calling rates of pups, and the response to the introduction of a novel physical object. Alterations in behavioural patterns which were expected a priori were observed but there appeared to be no changes in behaviour associated with any one selection criterion. Estimates of the genetic correlations between selected and behavioural traits were, with one exception, generally less than 0.1 in magnitude and not significantly different from zero (the exception was food intake in lines selected on body weight). Assuming that mice are accurate models for commercial species, then these results have important implications for animal welfare: they demonstrate that large scale behavioural changes do not arise as an inevitable consequence of intense long-term selection on traits of economic importance in commercial species.