Differential sensitivity of climate conditions on birth weight genetic values in mice divergently selected for birth weight residual variance.

Two mice lines obtained by divergent selection for birth weight residual variance were used to determine whether environmental factors could differently affect the homogeneous and heterogeneous lines. The maximum temperature 1 wk before parturition (MXTW) had the higher impact on the birth weight of the animals. A random regression model showed the individual trajectory of birth weight throughout the changes in MXTW. It was evident that the homogeneous line is less susceptible to changes in climate. This result, therefore, supports the hypothesis that the selection for homogeneity in production animals is more advantageous. More robust animals are obtained that can better cope with changes in climate without compromising their productive traits.