Variance of gametic diversity and its application in selection programs.

Area of Science:

• Animal Breeding and Genetics
• Quantitative Genetics
• Genomic Selection

Background:

• Traditional breeding values may not fully capture an individual's potential for progeny with extreme traits.
• Gametic diversity variance (σ²_gamete) offers a metric to identify individuals likely to produce offspring with extreme breeding values.
• Accurate estimation of σ²_gamete is crucial for enhancing genetic progress in livestock populations.

Purpose of the Study:

• To estimate gametic variance (σ²_gamete) from routine genomic evaluations.
• To integrate σ²_gamete into a selection criterion alongside breeding values to improve genetic gain.
• To develop and validate a new index, relative predicted transmitting ability, for more effective genetic selection.

Main Methods:

• Developed an analytical approach to estimate σ²_gamete using the sum of binomial variances across all quantitative trait loci (QTL).
• Utilized simulation studies to verify the predictability of the analytical approach across various scenarios.
• Applied the method to US genomic evaluations for Holstein and Jersey cattle, considering factors like the DGAT1 gene and inbreeding.

Main Results:

• The prediction accuracy for σ²_gamete ranged from 0.49 to 0.85, demonstrating the method's reliability.
• Single Nucleotide Polymorphism (SNP) data proved sufficient for estimating σ²_gamete, with inclusion of low minor allele frequency markers and marker covariance improving accuracy.
• Simulations indicated that incorporating σ²_gamete could lead to an additional 16% genetic gain over 10 generations.
• The DGAT1 gene significantly influenced σ²_gamete for production traits in cattle; inbreeding had a minor impact on gametic variability.

Conclusions:

• Gametic variance (σ²_gamete) is a computationally feasible and valuable parameter for enhancing selection programs.
• The proposed relative predicted transmitting ability index effectively utilizes genetic potential, surpassing traditional methods.
• The application of σ²_gamete in cattle breeding demonstrates its practical utility for improving genetic progress and managing genetic diversity.