BRAHMAN NEWS MARCH 2015 ISSUE #186 PAGE 22
By Paul Williams TBTS TECHNICAL OFFICER
A significant enhancement was made to the Brahman GROUP BREEDPLAN analysis in November with the incorporation of Direct Genomic Values in the 200 Day Weight and Days to Calving EBVs.
A major focus within the Cooperative Research Centre for Beef Genetic Technologies (Beef CRC) was to use phenotypic records and SNP genotypes to develop prediction equations for a range of economically important traits. These equations have subsequently been validated by the Animal Genetics Breeding Unit (AGBU) to generate Direct Genomic Values (DGVs) on both the CRC animals and animals within the Brahman population. For Brahmans, a DGV for post-weaning weight (PWT) with an accuracy of 0.27 to predict 200 day weight and a Days to Calving DGV with an accuracy of 0.35, has been developed using phenotypes and genotypes from the Beef CRC northern reproduction project.
The AGBU analysis used 2068 Brahmans with imputed 770K SNP genotypes to estimate the genomic accuracies of the resulting DGVs. In the analyses the DGVs were coincided as a trait along with the target BREEDPLAN trait. For the PWT DGV this was analysed with the BREEDPLAN 200 Day Weight as the second trait. The reproductive DGVs for early female reproduction (age at puberty and post-partum anoestrus interval) were shown to not be independent and consequently combined into a single DGV for DTC using an estimate of the genetic correlation between the two DGVs and the correlation with the Days to Calving EBV.
The estimated genomic accuracies obtained were used to blend the DGV into the EBVs generated from a full Brahman BREEDPLAN evaluation. The EBVs and accuracies on the 2068 genotyped industry animals for 200 Day Weight and Days to Calving were compared with and without the blended DGVs.
The DGVs on each individual were blended into the existing Days to Calving EBV using the 0.35 genomic accuracy. The mean of the Days to Calving EBV pre and post blending on the 2068 animals was the same, however the change in EBV were dependent on the existing DTC accuracy. For example animals with high accuracy EBV changed little post blending, whereas animals with low accuracy EBVs changed considerably (change in EBV ranged from -14.9 days to +11.6 days) with the inclusion of the DGV information.
The blending of the DGVs increased the accuracy of the Days to Calving EBV on average by 10%. Figure 1 plots the existing DTC accuracy against the new DTC EBV accuracy after blending of the DGV for the 2068 animals. The effect is not the same for all animals and depends on the level of the existing accuracy. (Change in EBV accuracy ranged from 0 to 33%). For animals with low DTC EBV accuracies (<20%) the inclusion of the DGV lifted the accuracy considerably, whereas for the high accuracy animals the inclusion of DGV had little, or no effect on the DTC EBV accuracy.
The PWT DGV was blended into the 200 Day Weight EBV of the 2068 animals. Due to the low genomic accuracy of 0.26 the change to the EBV and accuracy was very small. While there was no change in the average EBV, actual change in 200 Day Weight EBV ranged from -9.1 to +5.8. Accuracy overall only increased by 1% but ranged from 1 to 24%. The largest changes was associated with the lowest pre blending accuracy.
Though the genomic accuracies of both the PWT and DTC DGVs are low, the blending of the DTC DGV into the BREEDPLAN analysis has yielded significant improvement in the genetic evaluation of days to calving. While the accuracy increases for DTC are only modest, it would take several years to generate enough daughters to achieve a similar accuracy through performance recording. For example a young bull with low DTC accuracy could achieve a DTC EBV with blended DGVs information equivalent to having 8-9 daughters with a days to calving performance record. This presents the opportunity for a more rapid rate of genetic gain for days to calving through earlier and higher accuracy genetic selection based on DGV blended EBVs. The improvements in 200 day weight EBV are very small but will still enhance those animals with very low accuracy.
Figure 2. Genomics shown in traits observed on animals with DGV blended EBVs
The DGVs of the 2068 animals used to calculate the DGV genomic accuracies were included in the November Brahman GROUP BREEDPLAN analysis and these animals now have DGV blended EBVs for DTC and 200 Day Weight. These animals are identified on Internet Solutions by having Genomics recorded in the in the traits observed area as shown in Figure 2 It is important to note that only the 2068 Brahman animals mentioned currently have DGVs calculated and there is no flow-on effect of these DGVs to other correlated traits or to close relatives.
Further information is available from:
Paul Williams at TBTS in Rockhampton on Ph: (07) 4927 6066 or Email: email@example.com