The contribution of dominance and inbreeding depression in estimating variance components for litter size in Pannon White rabbits

Abstract

In a synthetic closed population of Pannon White rabbits, additive (VA ), dominance (VD ) and permanent environmental (VPe ) variance components as well as doe (bF d ) and litter (bF l ) inbreeding depression were estimated for the number of kits born alive (NBA), number of kits born dead (NBD) and total number of kits born (TNB). The data set consisted of 18,398 kindling records of 3883 does collected from 1992 to 2009. Six models were used to estimate dominance and inbreeding effects. The most complete model estimated VA and VD to contribute 5.5 ± 1.1% and 4.8 ± 2.4%, respectively, to total phenotypic variance (VP ) for NBA; the corresponding values for NBD were 1.9 ± 0.6% and 5.3 ± 2.4%, for TNB, 6.2 ± 1.0% and 8.1 ± 3.2% respectively. These results indicate the presence of considerable VD . Including dominance in the model generally reduced VA and VPe estimates, and had only a very small effect on inbreeding depression estimates. Including inbreeding covariates did not affect estimates of any variance component. A 10% increase in doe inbreeding significantly increased NBD (bF d = 0.18 ± 0.07), while a 10% increase in litter inbreeding significantly reduced NBA (bF l = -0.41 ± 0.11) and TNB (bF l = -0.34 ± 0.10). These findings argue for including dominance effects in models of litter size traits in populations that exhibit significant dominance relationships.

Estimation of additive and dominance variance for litter size components in rabbits

“…Pearson's correlations showed the same tendencies as observed for the rank correlations but slightly higher values were found (Table 4). In the Pannon White rabbit population Nagy et al (2013) reported Spearman's rank correlations between breeding values estimated with the different single-trait models close to unity for NBA, NBD, and TNB. Similarly, Gallardo et al (2010) observed that the estimated breeding values of harvest body weight in Coho salmon showed correlation close to unity when the applied single-trait models differed only in the inclusion of the dominance effects.…”

“…However, Nagy et al (2011) evaluated the records of the first four parities only over a shorter period thus the size of the evaluated dataset was substantially smaller (3413 kindling records) than in the present study. In the Pannon White rabbit population Nagy et al (2013) used numerous models. When the models contained the same effects as the basic model of this study, slightly lower h 2 and p 2 estimates were obtained for NBA (0.057 and 0.066), NBD (0.022 and 0.015), and TNB (0.064 and 0.069) compared to the findings of this study.…”

“…Similarly to this last finding, Fernández et al (2010) observed the lack of dominance for litter size at weaning in a maternal line of rabbits (d 2 = 0.017). According to the results of a recent study Nagy et al (2013) …”

“…In these species the results of several studies are available predicting the nonadditive variance components and comparing the results of genetic evaluations with and without nonadditive (and/ or other) effects (Winkelman and Peterson, 1994;Lutaaya et al, 2001;Mielenz et al, 2006). Yet according to our best understanding so far only one study has been conducted for rabbits (Nagy et al, 2013). Our hypotheses to be tested were that extending the models used for genetic evaluation with the dominance effects has an effect on the predicted breeding values and on the ranking of the evaluated animals.…”

Genomic dissection of inbreeding depression: a gate to new opportunities

“…Incomplete and unbalanced pedigree information is one source of errors (Cassell et al, 2003) in estimation of inbreeding depression. In experimental analyses, different strategies have been applied to account for the bias introduced by incomplete pedigrees (VanRaden, 1992;Lutaaya et al, 1999;González-Recio et al, 2007 andNagy et al, 2013). Pedigree errors are another source of errors that is present in livestock populations (Leroy and Baumung, 2011).…”