Restricting inbreeding while maintaining selection response for weight gain in Mus musculus

Abstract

An experiment with mice was designed to test the relative efficiency of three selection methods that help to minimize the rate of inbreeding during selection. A common house mice (Mus musculus) population was selected for 17 generations to increase the weight gain between 21 and 42 days. The population was split at random into three lines A, B and C where three selection methods were applied: individual selection and random mating, weighted selection with random mating and individual selection with minimum coancestry mating, respectively. There were three replicates for each line. Cumulated selection response was similar in the three lines, but there were differences in the level of inbreeding attained (in percentage): 31.24 (method A), 24.72 (method B) and 27.88 (method C). As consequence, lines B and C (weighted selection and minimum coancestry) showed a lower value of deterioration of fitness traits (the intrauterine mortality and the mortality at birth) than line A (random mating).

Correlated genetic trend in the environmental variability of weight traits in mice

“…They were estimated only for discussion purposes of the trends. Heritabilities and litter ratios were reasonably in agreement with previous estimates under univariate analyses with the same data set (Ibá ñ ez-Escriche et al, 2008a; Moreno et al, 2011). Genetic correlations between the selected trait WG and the correlated W21 and W42 traits were 0.68 and 0.94, respectively.…”

“…The females were not evaluated nor selected. Other details of the design can be found in Ibá ñez-Escriche et al (2008a) and Moreno et al (2011).…”

“…This analysis has already been performed to analyse the genetic trend of WG by Moreno et al (2011) and as they argued, the maternal genetic effect was not explicitly fitted in the model because previous analysis on performances, fitting together both litter and maternal genetic effects, showed that the litter was carrying all the variability explained by the maternal genetic effects. -The Heterogeneity Model (HE) by SanCristobal-Gaudy et al (1998), in which it is assumed that the environmental variance was heterogeneous and partly under genetic control, fitted the same effects as in Model HO both for the mean of the trait and for its environmental variability.…”

“…Thus, models analysing parameters concerning environmental variability could present difficulties in disentangling the total phenotypic variability and should be carefully checked in these scenarios. Moreno et al (2011) have shown an important success of artificial selection after 17 generations for weight gain in mice, comparing three different selection methods and concluding that all gave similar responses.…”

“…Therefore, selection experiments have been conducted in mice (Ferná ndez et al, 1998;Moreno et al, 2011) to quantify the expected success before implementing them in other mammals. Populations under selection, such as the presently analysed, are expected to theoretically reduce their genetic variability (Falconer and Mackay, 1996).…”