The Dairy Genomics Program (DGP) was initiated in 2016 with the primary aim to establish a reference population for dairy breeds which can be used to develop genomic estimated breeding values (GEBVs) which according to principle and function should improve the EBV’s , as calculated in the conventional way. The reference population (RP) was established in Phase 1 of the DGP which ended in March 2019 and the question was how did it benefit us. This was also the question posed by the authors cited below, who then did a GEBV analysis on Jersey cattle data and compared the GEBVs with previous EBV estimates. The Jerseys have been receiving BLUP (EBVs) and MACE breeding values for production, functional type, udder health, fertility and longevity traits for several years.
A RP of 1186 and a validation population of 128 was established, enabling the inclusion of genomic information in estimation of breeding values, based on the INTERBULL verified Logix Genetic Evaluations and a Single-Step approach, using Mix99, to present the industry with GEBVs. These GEBVs reflect the expression of genes in the SA environment, based on the genetic variation and gene frequencies of the SA Jersey population.
The results showed a significant increase in reliability of estimates, especially for traits of low heritability, ranging from an average increase of 6% for milk yield (MY) to 13% for functional herd life and inter-calving period (ICP) in the validation population. Individual animals’ reliabilities increased as much as 19% for MY. For animals in the RP, Pearson correlations between GEBVs and traditional EBVs ranged from 0.94 for ICP to 0.98 for MY, whereas for animals in the validation population, Pearson correlations ranged from 0.87 for ICP to 0.94 for MY. As expected, re-ranking of genetic merit was higher in the validation population compared to that of animals in the RP.
Conclusion: The results showed a significant improvement with the GEBV estimations.
RR van der Westhuizen, BE Mostert & J van der Westhuizen, 2019. Implementing Genomic Selection following a Single-Step Approach for South African Jersey Cattle. In: Proc. of the SALHC 2019, Port Elizabeth, 2-5 June 2019.