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Results – EBVs reliably predict performance

This project has indicated that the EBVs of the sires entered in Cohorts 1, 2 and 3 provided a reliable prediction of the performance of their progeny.

Calving Ease (Birth Weight, Gestation Length)

The difference between the average Birth Weight EBV of the highest and lowest 10 Birth Weight EBV sires in each cohort was on average 3.4 kg, across cohorts 1, 2 and 3. This equates to a predicted difference in the average birth weight of progeny of sires in both groups of 1.7 kg. Note: the predicted difference is only half the difference in the EBVs as the sires only contribute to half of their progeny’s genetics.

When the average birth weight of the progeny from the highest and lowest 10 Birth Weight sires was measured, the actual difference in birth weight was 1.9 kg, demonstrating the EBVs were accurately predicting the breeding value of sires for birth weight.

Similarly, the difference between the average Gestation Length EBV of the highest and lowest 10 Gestation Length EBV sires in each cohort was on average 5.1 days across cohorts 1, 2 and 3. Therefore it was predicted that the progeny of the 10 sires with the lowest Gestation Length EBVs would be born, on average, 2.5 days earlier than the progeny of the 10 sires with the highest Gestation Length EBVs.

When the gestation length data of progeny from both groups of sires was collated, the difference was 2.6 days, and closely aligned with the difference predicted by the sire EBVs.

Growth (200, 400 & 600 Day Weights)

The difference between the average EBV of the highest and lowest 10 EBV sires for 200 Day Growth, 400 Day Weight and 600 Day Weight EBV in each cohort was on average 15.2 kg, 25.2 kg and 36.6 kg respectively, across cohorts 1, 2 and 3. This equates to a predicted difference in the average weight of progeny of sires in both groups of 7.6 kg, 12.6 kg and 18.3 kg at 200, 400 and 600 days of age.

When weighed, the actual difference in the weight of progeny was 5.2 kg, 10.2 kg and 17.0 kg, and demonstrated the EBVs of the sires provided a reliable indication of their genetics for growth.

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

The difference between the average EBV of the highest and lowest 10 EBV sires for Carcase Weight, Eye Muscle Area, Rib Fat, Rump Fat and Intramuscular Fat EBV in each cohort was on average 21.7 kg, 5.7 cm2, 2.5 mm, 3.0 mm and 2.0% respectively, across cohorts 1, 2 and 3. This equates to a predicted difference in the sires average carcase progeny performance of 10.9 kg dressed carcase weight, 2.8 cm2 eye muscle area, 1.2 mm rib fat depth, 1.5 mm rump fat depth and 1.0% intramuscular fat.

When the steer progeny were slaughtered and abattoir carcase measurements collected, the actual difference in the carcase performance weight of progeny was 18.2 kg dressed carcase weight, 2.8 cm2 eye muscle area, 1.1 mm rib fat depth, 1.3 mm rump fat depth and 1.3% intramuscular fat.

This demonstrates that the EBVs of sires in cohorts 1, 2 and 3 provided an accurate prediction of their carcase genetics, and can be used with confidence when selecting animals for superior carcase genetics.

Fertility (Days to Calving)

The difference between the average Days to Calving EBV of the highest and lowest 10 Days to Calving EBV sires in each cohort was on average 4.1 days across cohorts 1, 2 and 3. Therefore it was predicted that the heifer progeny of the 10 sires with the lowest Days to Calving EBVs would calve, on average, 2.1 days earlier than the progeny of the 10 sires with the highest Days to Calving EBVs.

When the heifer progeny were calved down at 2 years of age and their calving records collated, the progeny sired by the lowest Days to Calving EBV sires calved on average, 1.0 days earlier than the progeny sired by the highest Days to Calving EBV sires.

Feed Efficiency (Net Feed Intake – Feedlot)

The difference between the Net Feed Intake (Feedlot) EBV of the highest and lowest 10 NFI-F EBV sires in each cohort was on average 0.9 kg/day across cohorts 1, 2 and 3, indicating the progeny of the lowest NFI-F sires were predicted to eat 0.5 kg less feed per day for the same weight and rate of weight gain.

When the steer progeny were tested for feed intake at Tullimba Research Feedlot using Growsafe technology, the actual difference between the progeny of the high and low NFI-F EBV sire groups was 0.3 kg/day.