Genetic evaluation of litter size traits in Pannon Large rabbits

Genetic parameters and genetic trends for the number of kits born alive (NBA), number of kits born dead (NBD) and the total number of born kits were estimated in Pannon Large rabbits. Using the REML method 12 single trait models were examined. Heritability estimates were low for all traits and ranged between 0.07-0.08 (with standard errors 0.018-0.021) for NBA (5830 records), 0.01-0.02 (0.009-0.009) for NBD (6278 records) and 0.04-0.05 (0.015-0.018) for TNB (6278 records) from 1469 does. The ratios of the permanent environmental and the phenotypic variances exceeded of the heritability estimates and ranged between 0.11-0.16(0.016-0.018) for NBA, 0.06-0.07 (0.014-0.015) for NBD and 0.11-0.17 (0.014-0.017) for TNB. When characterizing the goodness of models bias values were practically zero for all traits and models. After identifying the best fitted model (containing parity, age of the doe and year-month of kindling effects) it was extended with dominance effects. As a result, heritability estimates decreased to 0.06 (0.028) for NBA, 0.02 (0.012) for NBD and 0.02 (0.022) for TNB. The relative importance of the permanent environmental effects also decreased to 0.09 (0.031) for NBA, 0.05 (0.024) for NBD and 0.07 (0.028) for TNB. Ratios of the dominance effects exceeded those of the heritability estimates and amounted to 0.27 (0.024) for NBA, 0.05 (0.013) for NBD and 0.38 (0.025) for TNB. When compared to the additive model, the model including dominance showed some confounding with additive genetic and with permanent environmental effects and reduced calculated genetics trends (0.035 vs 0.03, -0.0017 vs -0.003 and 0.016 vs 0.01 for NBA, NBD and TNB, respectively). Spearman rank correlation coefficients between breeding values of the additive and dominance models were high for all traits (0.96-0.98). When dominance effects were included some re-ranking was observed among the top ranked animals for every trait.