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Results – start & finish EBVs closely aligned

The project has illustrated that while the EBVs for some individual sires did change, there was on average, minimal change in the EBVs of the sires, and the sires’ initial EBVs aligned closely with their EBVs at the end of the program when their progeny had been comprehensively performance recorded.

Calving Ease (Birth Weight, Gestation Length)

In cohorts 1, 2 and 3 of the ASBP, the 10 sires in each cohort with the highest initial Birth Weight EBVs had an average initial EBV of +6.2 kg. By comparison, the average final Birth Weight EBV for these same sires was +6.6 kg, equating to a change of only 0.4 kg. The average accuracy of the initial and final Birth Weight EBVs for these sires increased from 75% to 94%.

Similarly, the 10 sires in each cohort with the lowest initial Birth Weight EBV had an average initial EBV of +2.8 kg. By comparison, the average final Birth Weight EBVs of these same sires was also +2.8 kg. The average accuracy of the initial and final Birth Weight EBVs for these sires increased from 78% to 95%.

For gestation length, the change in the average initial and final Gestation Length EBVs of the 10 sires with the highest initial EBVs in each cohort was only 0.2 days (-1.1 days versus -1.3 days), whereas the difference between the average initial and final Gestation Length EBVs of the 10 sires with the lowest initial EBVs was only 0.6 days (-6.1 days versus -6.7 days). The average EBV accuracy increased for the two groups of sires by 22% and 16% respectively.

Growth (200, 400 & 600 Day Weights)

The average initial EBV of the 10 sires in each cohort with the highest EBV for 200 Day Growth, 400 Day Weight and 600 Day Weight was +51 kg, +93 kg and +125 kg respectively. By comparison, the average final EBV for the same sires was +53 kg, +95 kg and +127 kg, representing a change of only 2 kg between the EBVs when the sires were entered in the ASBP and the EBVs when all the sires’ progeny performance data had been analysed for 200, 400 and 600 day weight. The increase in accuracy for these EBVs was 23% for 200 Day Growth (69 to 92%), 22% for 400 Day Weight (70% to 92%) and 21% for 600 Day Weight (71% to 92%).

Similarly, the average initial EBV of the 10 sires in each cohort with the lowest EBV for 200 Day Growth, 400 Day Weight and 600 Day Weight was +36 kg, +68 kg and +89 kg respectively. The average final EBV for the same sires was +37 kg, +71 kg and +89 kg, representing a change of only 1 kg, 3 kg and 0 kg. The increase in accuracy for the 200 Day Growth, 400 Day Weight and 600 Day Weight EBVs was 18%, 20% & 19% respectively.

Carcase Composition (Carcase Weight, Eye Muscle Area, Intramuscular Fat, Rib and Rump Fat)

For the carcass composition traits, the change in the average initial and final Carcase Weight EBVs of the 10 sires with the highest initial EBVs in each cohort was only 2 kg (+125 kg versus +127 kg), whereas there was no difference between the average initial and final Carcase Weight EBVs of the 10 sires with the lowest initial EBVs (Initial and Final EBVs both +89 kg). The average EBV accuracy increased for the two groups of sires by 21% and 19% respectively.

The average initial EBV of the 10 sires in each cohort with the highest EBV for Carcase EMA, IMF, Rib and Rump Fat was +7.8cm2, +2.8%, +1.0mm and +1.2mm respectively. By comparison, the average final EBV for the same sires was +8.1cm2, +2.8%, +1.1mm and +1.3mm. This represents a very small change in the carcase composition EBVs generated at the initial joining period to the EBVs generated when all the sire’s progeny carcass performance had been included in the analysis. The increase in accuracy for these EBVs was 27% for Carcase EMA (61% to 88%), 28% for Carcase IMF (59% to 87%), 26% for Carcase Rib Fat (63% to 89%) and 23% for Carcase Rump Fat (64% to 87%).

Similarly, the average initial EBV of the 10 sires in each cohort with the lowest EBV for Carcase EMA, IMF, Rib and Rump Fat was +2.2 cm2, +0.7%, -1.5mm and -1.7mm respectively. The average final EBV for the same sires was +2.1 cm2, +0.5%, -1.7mm and -1.5mm, representing a change of only 0.1 cm2, +0.2 %, 0.2mm and 0.2mm. The increase in accuracy for Carcase EMA, IMF, Rib and Rump Fat was 28%, 32%, 28% & 26% respectively.

Fertility (Days to Calving)

There were also minimal changes in fertility EBVs observed from the initial period at sire joining to the EBVs recorded at the completion of the trial after the heifer progeny had calved down at 2 years of age and all calving records collated and included in the Angus BREEDPLAN analysis. The difference in Days to Calving EBVs for the average of the highest ten sires in each cohort was 0.9 days (-1.4 days to -2.3 days), with an 18% increase in accuracy. A smaller difference in Days to Calving EBVs was observed when assessing the average of the lowest ten Days to Calving EBV sires in each cohort. The difference was calculated to be 0.2 days (-5.5 days to -5.3 days) with an accuracy increase of 16% (46% to 62%).

Feed Efficiency (Net Feed Intake – Feedlot)

For feed efficiency, the change in the average initial and final Net Feed Intake-Feedlot (NFI-F) EBVs of the 10 sires with the highest initial EBVs in each cohort was -0.22 kg/day (+0.70 kg/day versus +0.48 kg/day), whereas the difference between the average initial and final NFI-F EBVs of the 10 sires with the lowest initial EBVs was only +0.13 kg/day (-0.21 kg/day versus -0.08 kg/day). The average EBV accuracy increased for the two groups of sires by 32% and 34% respectively.