Genetic parameters for canalisation analysis of litter size and litter weight traits at birth in mice

Abstract

-The aim of this research was to explore the genetic parameters associated with environmental variability for litter size (LS), litter weight (LW) and mean individual birth weight (IW) in mice before canalisation. The analyses were conducted on an experimental mice population designed to reduce environmental variability for LS. The analysed database included 1976 records for LW and IW and 4129 records for LS. The total number of individuals included in the analysed pedigree was 3997. Heritabilities estimated for the traits under an initial exploratory approach varied from 0.099 to 0.101 for LS, from 0.112 to 0.148 for LW and from 0.028 to 0.033 for IW. The means of the posterior distribution of the heritability under a Bayesian approach were the following: 0.10 (LS), 0.13 (LW) and 0.03 (IW). In general, the heritabilities estimated under the initial exploratory approach for the environmental variability of the analysed traits were low. Genetic correlations estimated between the trait and its variability reached values of -0.929 (LS), -0.815 (LW) and 0.969 (IW). The results presented here for the first time in mice may suggest a genetic basis for variability of the evaluated traits, thus opening the possibility to be implemented in selection schemes.canalisation / variability / mice / litter size / litter weight

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

“…Once more, the present study suggests the existence of additive genetic control of the environmental variability, which has been reported by other authors for different weight traits in pigs (Bodin et al, 2002;Damgaard et al, 2001;Högberg and Rydhmer, 2000;Huby et al, 2003;Ibá ñ ez-Escriche et al, 2008b), in rabbits (Bodin et al, 2010;Garreau et al, 2004Garreau et al, , 2008, in snails or litter size, closely related to fitness, in sheep (SanCristó bal- Gaudy et al, 2001) in mice (Gutié rrez et al, 2006;Ibá ñ ez-Escriche et al, 2008a) in rabbits (Argente et al, 2010), in beef cattle (Neves et al, 2011), in broiler chickens (Mulder et al, 2009) and in alpacas (Cervantes et al, 2010), with a recent revision by Hill and Mulder (2010). The results presented in this study again suggest an additive genetic control of the environmental variability and different estimates of the variance components when using models that assume that environmental variance was heterogeneous.…”

Results of four generations of a canalising selection for rabbit birth weight

“…On a large sample of piglets, Damgaard et al (2003) as well as Huby et al (2003) found a positive genetic correlation between mean birth weight and within-litter standard deviation. In mice Gutiérrez et al (2006) found a lower genetic correlation using the present methodology than using a heteroscedastic model under a Bayesian approach (0.259 vs. 0.969). However Damgaard et al (2003) also reported a negative correlation between standard deviation of birth weight within-litter and mean growth rate of piglets.…”

“…Sorensen and Waagpetersen (2003) developed a Bayesian approach based on the SanCristobal model (SanCristobal-Gaudy et al, 1998) using the MCMC algorithm to compute posterior distributions. Gutiérrez et al (2006) compared this methodology with the present one, estimating the genetic parameters of litter size, litter weight and mean individual birth weight in mice with both methods. The heritability estimated using the present methodology for environmental variability of individual birth weight was very close to the one we obtained (0.014).…”

“…The permanent environmental effect DCE n was excluded from model (2) because it is basically the conceptual trait which is analysed in this step (Gutiérrez et al, 2006).…”

Developments in statistical analysis in quantitative genetics

“…Statistical evidence for genes affecting environmental variance has come from fitting the model to data on litter size in pigs (Sorensen and Waagepetersen 2003), adult weight in snails (Ros et al 2004), uterine capacity in rabbits ) body weight in poultry (Rowe et al 2006), slaughter weight in pigs (Ibáñez et al 2007) and litter size and weight at birth in mice (Gutierrez et al 2006) Stronger support, not derived from fitting the genetically structured heterogeneous variance model, but from analyses of elegantly designed experiments with isogenic chromosome substitution lines of Drosophila, was provided by Mackay and Lyman (2005). Here, homozygote inbred lines that differed in chromosome 2 or 3 were created, and variation between individuals in abdominal and sternopleural bristle number was computed.…”