COMPARISONS

Using EBVs for Making Comparisons Between Animals

By Peter Parnell, CEO, Australian Angus

When using EBVs to assist in selection decisions, it is important to remember that only half the EBV differences between animals are expressed in their progeny.

For example, when comparing the expected difference in the 400-Day weights of calves from two bulls, you need to consider half the difference in EBVs between the bulls, multiplied by the expected number of calves sired during the normal life span of a bull in your herd.

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Example: 400-day Wt. EBV
BULL  A: +40 kg
BULL  B: +20 kg
Expected difference in 400 day weight:
½ x (40 kg – 20 kg) = 10 kg  per calf

Total gain over 3 years of use, with 25 calves per year:
25 calves x 3 years x 10kg = 750kg

(plus further benefits from the future improved performance of daughter’s calves)

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This simple calculation can be a useful guide to assist in determining the potential extra revenue you can expect from using a bull with superior growth EBVs. Similar calculations can be made for determining the expected effect on progeny performance of differences in other EBVs.

In selecting bulls for use in your herd, it is often helpful to compare their EBV figures relative to the whole drop of bulls for sale. During 2010 many of the bulls for sale will come from the 2008 calf crop.

The table on that lists the EBV percentile bands for the 2008 born calves, for each of the traits included in the Autumn 2010 Angus GROUP TACE (TransTasman Cattle Evaluation) analysis. This table provides a guide to the relative ranking of any animal, compared with the total 2008 calf crop.

For example, a bull with a 600-Day Wt EBV of +110 kg, and a Birth Wt EBV of +5.9 kg is in the highest 5% of the breed for 600-Day Wt and in the lowest 20% of the breed for Birth Wt, compared to all recorded calves born in 2008. A bull with a ‘Days to Calving’ EBV of –4.9 days would be in the highest (most favourable) 5% of the breed for that trait.