Genetic correlations between two strains of Durocs and crossbreds from differing production environments for slaughter traits

Abstract

The aim of this study was to estimate the genetic correlations between 2 purebred Duroc pig populations (P1 and P2) and their terminal crossbreds [C1 = P1 x (Landrace x Large White) and C2 = P2 x (Landrace x Large White)] raised in different production environments. The traits analyzed were backfat (BF), muscle depth (MD), BW at slaughter (WGT), and weight per day of age (WDA). Data sets from P1, P2, C1, and C2 included 26,674, 8,266, 16,806, and 12,350 animals, respectively. Two-trait models (nucleus and commercial crossbreds) for each group included fixed (contemporary group, sex, weight, and age), random additive (animal for P1 and P2 and sire for C1 and C2), random litter, and random dam (C1 and C2 only) effects. Heritability estimates (+/-SE) for BF were 0.46 +/- 0.04, 0.38 +/- 0.02, 0.32 +/- 0.02, and 0.33 +/- 0.02 for P1, P2, C1, and C2, respectively. Heritability estimates for MD were 0.31 +/- 0.01, 0.23 +/- 0.02, 0.19 +/- 0.01, and 0.12 +/- 0.01 for P1, P2, C1, and C2, respectively. The estimates for WGT and WDA were 0.31 +/- 0.01, 0.21 +/- 0.02, 0.16 +/- 0.01, and 0.18 +/- 0.01 and 0.32 +/- 0.01, 0.22 +/- 0.02, 0.16 +/- 0.01, and 0.19 +/- 0.01, respectively. Genetic correlations between purebreds and crossbreds for BF were 0.83 +/- 0.09 (P1 x C1) and 0.89 +/- 0.05 (P2 x C2), for MD 0.78 +/- 0.05 (P1 x C1) and 0.80 +/- 0.08 (P2 x C2). For WGT and WDA, the correlations were 0.53 +/- 0.08 (P1 x C1), 0.80 +/- 0.10 (P2 x C2), and 0.60 +/- 0.07 (P1 x C1) and 0.79 +/- 0.09 (P2 x C2), respectively. (Co)variances in crossbreds were adjusted to a live BW scale. Compared with purebreds, the genetic variances in crossbreds were lower, and the residual variances were greater. Sire variances in crossbreds were approximately 20 to 30% of the animal variances in purebreds for BF and MD but were 13 to 25% for WGT and WDA. The efficiency of purebred selection on crossbreds, assessed by EBV prediction weights, ranged from 0.43 to 0.91 for line 1 and 0.70 to 0.92 for line 2. When nucleus and commercial environments differ substantially, the efficiency of selection varies by line and traits, and selection strategies that include crossbred data from typical production environments may therefore be desirable.

Estimation of genetic parameters for birth weight, preweaning mortality, and hot carcass weight of crossbred pigs1

“…The mean HCW of 93.37 kg with a SD = 8.60 kg is in agreement with HCW reported by Fix et al (2010) but is somewhat higher than the final weight reported by Zumbach et al (2007) in similar crossbred populations. On average, litter had 12.1 ± 3.8 piglets born alive.…”

“…Estimated residual variances were high compared to other variance components for each trait (0.070 for BWT, 1.000 for PWM, and 56.228 for HCW). The relatively high residual variances could be due to the variation of the Mendelian sampling, which is not included directly in the model (Zumbach et al, 2007). Therefore, the Mendelian sampling becomes part of the residual and contributes to the increasing of the estimated residual variance.…”

“…To separate the animal additive genetic effects into sire and dam components as in Zumbach et al (2007), a model with sire additive genetic effects and dam effects was considered. This allowed the estimation of sire genetic covariance based on their crossbred progeny.…”

Estimation of genetic associations between reproduction and production traits based on a sire and dam line with common ancestry

“…Production traits Heritabilities for production traits were estimated at 0.29, 0.50 and 0.41 for ADG, BF and MD, respectively, in the sire line and 0.29 and 0.42 for ADG and BF, respectively, in the dam line. Heritabilities for ADG and BF were similar to values in literature which ranged from 0.23 to 0.40 for ADG (Ferraz and Johnson, 1993;Serenius and Stalder, 2004;Rosendo et al, 2007a) and from 0.30 to 0.51 for BF Serenius and Stalder, 2004;Zumbach et al, 2007). The slightly higher heritability for BF in the sire line compared to the dam line was unexpected because breeding in the sire line primarily focused on reduction of BF, while this was of lesser emphasis in the dam line.…”

“…The slightly higher heritability for BF in the sire line compared to the dam line was unexpected because breeding in the sire line primarily focused on reduction of BF, while this was of lesser emphasis in the dam line. The heritability for MD was slightly higher than previously reported heritabilities which ranged from 0.12 to 0.31 (Hermesch et al, 2000b;Zumbach et al, 2007). Genetic and phenotypic correlations among the production traits were approaching zero in the dam line.…”