P.PSH.1211 - Validation of pooled DNA gEBV for Brahman Commercial Cow Fertility Final Report

Summary

The productivity of cow herds is an important underpinning metric for industry profitability, and as the CRC for Beef Genetic Technologies demonstrated, a clear target for genetic improvement. In previous work, CSIRO and The University of Queensland have worked with Brahman producers and bull breeders to demonstrate that reproductive performance data from commercial Brahman cow herds can be used as phenotypic information to drive genomic predictions of daughter fertility in bulls. The current project was undertaken to move this novel application of genomics closer to commercial application by calculating the accuracy of the DNA-based predictions (typically denoted as GEBV for genomic-estimated breeding values) and by determining their cost‐benefit to producers and bull‐breeding operations.

Objectives

• Determine the accuracy of pooled-DNA GEBV for commercial cow fertility within participating herds and for the Brahman breed more generally.
• Calculate the cost-benefit of adopting the technology.
• Build the 'reference population' for Brahman cow fertility GEBV by collecting additional phenotypes and genotypes.
• Develop methodology for integrating GEBV for commercial cow fertility into Brahman group BREEDPLAN services.

Key findings

• The GA2CAT results are easy to interpret, promoting adoption by commercial producers wanting to improve the reproductive performance of their herds.
• The GA2CAT method will not be influenced by the phenotype scoring system allowing producers to tailor selection strategies to their production system.
• The population variation of GA2CAT values reflects the degree of relatedness between testing and reference populations: as would be expected, GA2CAT predictions are valid for the most closely related cattle populations.
• The negative correlation between GA2CAT values for Wet and Early Pregnancy and GEBV of DTC (-0.2) further indicates GA2CAT can be used as a good tool to select bulls.

Benefits to industry

• The new metric – weighted average of GA2CAT values for different categories, is easy to derive and most importantly it provides commercial bull-buyers a single ‘ranking’ value for each candidate bull so that they can readily make the decisions about which bulls to choose.
• The population variation of GA2CAT values reflects the degree of relatedness between testing and reference populations: as would be expected, GA2CAT predictions are valid for the most closely related cattle populations.
• A newly developed executable computer program for routine calculation of GA2CAT values for candidate bulls will promote adoption by commercial producers wanting to improve the reproductive performance of their herds.

MLA action

The key findings from this report and future research recommendations will be shared with the National Livestock Genetics Consortium.

Future research

• As a low heritability and imbalanced multi-class trait, the genomic selection for 2nd joining pregnancy and lactation status presents challenges. The new metric 'GA2CAT' is recommended to be applied in conjunction with individual bull’s BBSE (Bull Breeding Soundness Examination) results when selecting candidate bulls for mating.
• Due to the 2019 flood, the project could only collect the candidate bulls from Gipsy Plains during the 2021–2022 and 2022–2023 seasons. As result, there has not been the ability to conduct a systematic validation of the accuracies of genomic prediction by our new method GA2CAT for all individual bulls that sired the MDH cows (with 2nd joining pregnancy and lactation status records) from 2019–2022. A future study is needed to evaluate the accuracy of the new prediction tool.
• Further research is required to identify a new phenotype that is more heritable than the phenotype of pregnancy and lactation status.