Abstract
Livestock breeding has shifted during the past decade toward genomic selection. For the estimation of breeding values in purebred breeding schemes, genomic best linear unbiased prediction has become the method of choice. Systematic crossbreeding with the aim to utilize heterosis and breed complementary effects is widely used in livestock breeding, especially in pig and poultry breeding. The goal is to improve the performance of the crossbred animals. Due to genotype-by-environment interactions, imperfect linkage disequilibrium, and the existence of dominance and imprinting, purebred and crossbred performances are not perfectly correlated. Hence, more complex genomic models are required for crossbred populations. This study reviews and compares such models. Compared to purebred genomic models, the reviewed models were of much higher complexity due to the inclusion of dominance effects, breed-specific effects, imprinting effects, and the joint evaluation of purebred and crossbred performance data. With the model assessment work conducted until now, it is not possible to come to a clear recommendation as to which existing method is most suitable for a specific breeding program and a specific genetic trait architecture. Since it is expected that a superior method includes all the different genetic effects in a single model, a dominance model with imprinting and breed-specific SNP effects is proposed. Further progress could be made by assuming realistic covariance structures between the genetic effects of the different breeding lines, and by using larger marker panels and mixture distributions for the SNP effects.
Highlights
The crossing of different lines or breeds is widely used in animal breeding with the main aim to produce superior offspring
Genomic models for crossbred data are of much higher complexity than models for purebred data, which results from the inclusion of dominance effects, breed-specific effects, imprinting effects, and from the joint evaluation of PP and CP
Much research has already been done to develop genomic models for crossbred data, it can be expected that further progress can be made by developing statistical models that include all the different genetic effects in a single model, assume realistic covariance structures between the genetic effects of different breeding lines, use large marker panels, and assume realistic distributions for the SNP effects
Summary
The crossing of different lines or breeds is widely used in animal breeding with the main aim to produce superior offspring. This superiority results from heterosis and from breed complementary effects. The level of organization in such a system is high and it is sometimes difficult to utilize by-products, such as male offspring of mother lines These schemes can be predominantly found in livestock species with a high female reproduction rate such as pigs and poultry. The female crossbreds are used as parents to breed the generation These systems are sometimes implemented in Genomic Models for Crossbred Data livestock species with a low female reproduction rate such as cattle. Since there are substantial non-additive effects for reproduction traits in dairy cattle (Jiang et al, 2017), the aims of crossbreeding in dairy cattle are to improve reproduction traits and other functional traits by exploiting heterosis and imprinting and by removing inbreeding depression (Sørensen et al, 2008; Buckley et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
