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

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 ( r_pc ) is generally lower than 1. Accurate estimates of the r_pc are needed, so that breeders can decide if they should collect data from CB animals. r_pc can be estimated either from pedigree or genomic relationships, which may produce different results. With genomic relationships, the r_pc 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 r_pc 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 r_pc estimates depended on the relationship matrix used. Estimates were 5 to 25