Estimating the purebred-crossbred genetic correlation of body weight in broiler chickens with pedigree or genomic relationships

Abstract

Background In pig and poultry breeding programs, the breeding goal is to improve crossbred (CB) performance, whereas selection in the purebred (PB) lines is often based on PB performance. Thus, response to selection may be suboptimal, because the genetic correlation between PB and CB performance ( ) is generally lower than 1. Accurate estimates of the are needed, so that breeders can decide if they should collect data from CB animals. can be estimated either from pedigree or genomic relationships, which may produce different results. With genomic relationships, the estimate could be improved when relationships between purebred and crossbred animals are based only on the alleles that originate from the PB line of interest. This work presents the first comparison of estimated and variance components of body weight in broilers, using pedigree-based or genotype-based models, where the breed-of-origin of alleles was either ignored or considered. We used genotypes and body weight measurements of PB and CB animals that have a common sire line. Results Our results showed that the estimates depended on the relationship matrix used. Estimates were 5 to 25% larger with genotype-based models than with pedigree-based models. Moreover, estimates were similar (max. 7% difference) regardless of whether the model considered breed-of-origin of alleles or not. Standard errors of estimates were smaller with genotype-based than with pedigree-based methods, and smaller with models that ignored breed-of-origin than with models that considered breed-of-origin. Conclusions We conclude that genotype-based models can be useful for estimating , even when the PB and CB animals that have phenotypes are closely related. Considering breed-of-origin of alleles did not yield different estimates of , probably because the parental breeds of the CB animals were distantly related. Electronic supplementary material The online version of this article (10.1186/s12711-019-0447-9) contains supplementary material, which is available to authorized users.

Genetics of crossbreeding

“…This was in line with our expectations, because with divergent selection, the difference in allele frequencies between parental lines increases, causing an increase in the differences between average effects for PB and CB performance (Wei et al 1991;Baumung et al 1997). Across scenarios, the realized varied from 0.6 to 0.99, covering a large range of what is observed empirically (Wei and van der Werf 1995;Besbes and Gibson 1999;Newman et al 2002;Lukaszewicz et al 2015;Mulder et al 2016;Duenk et al 2019b).…”

“…The dam lines used (B and C) have been selected on egg production traits, whereas the sire line A has been selected on male fertility traits, along with growth, yield, and feed efficiency. The three parent lines (A, B, C) were genetically distant, as shown by the principal component analysis in Duenk et al (2019b).…”

“…Previously, in Duenk et al (2019b), we estimated genetic parameters for BW7 and BW35 with data from PB and CB animals that were housed in the same environment and that originated from a common group of sires. The estimated heritability of BW7 was 0.09 for PB performance and 0.18 for CB performance, and that of BW35 was 0.22 for PB performance and 0.23 for CB performance.…”

“…The can be lower than one due to differences in trait definition between PB and CB performance (Lo et al 1997;Zumbach et al 2007), due to genotype by environment interactions (GxE) (Falconer 1952;Lutaaya et al 2001), and due to genotype by genotype interactions (GxG) in combination with allele frequency differences between parental lines (Wei et al 1991;Baumung et al 1997;Duenk et al 2019b). GxG interactions are also known as non-additive genetic effects (i.e.…”

“…The aim of such breeding programs is usually to maximize crossbred (CB) performance, while selection decisions are made in the parental lines, usually based on measurements of purebred (PB) performance. As a result, the response to selection in CB performance depends partly on the genetic correlation between PB and CB performance ( ), which is generally lower than one across species and trait categories (Wei and van der Werf 1995;Besbes and Gibson 1999;Newman et al 2002;Lukaszewicz et al 2015;Mulder et al 2016;Duenk et al 2019b). Hence, is an important parameter in breeding programs of pig and poultry.…”