With over 26,000 farmers now in the Beef Data Genomics Programme (BDGP), and with AI in progress in some autumn herds and spring herds gearing up for breeding, we look at some of the key decisions you need to make to increase the maternal attributes of your herd.

Use 80% four- or five-star bulls

If you are using AI and partaking in the scheme, then it is essential that more than 80% of the bulls used through AI are four or five stars. This can be on either the terminal or maternal index.

This allows farmers breeding well-conformed calves for the export market or high-value domestic market to continue to use top bulls on the terminal index to do so.

In addition, if a farmer wishes to produce replacement heifers, by choosing AI sires that are ranked either four or five stars on the replacement index, this will help them to breed heifers which have high replacement values. This should help the farmers meet the conditions of the scheme under the replacement strategy requirement.

Advantages of AI

Using AI to breed replacements has significant advantages for farmers. While the use of AI may not be feasible for every farmer, where AI is being used, targeting the correct sire selection on the more maternal cows in the herd will help to increase the proportion of four- and five-star heifers in the herd.

For example, using a reliable AI bull that has five stars on a three- or four-star cow should result in a star rating of four to 4.5 stars for the resultant calf.

The key advantage with the use of AI sires is high reliabilities. According to the ICBF, approximately 20% of stock bulls will move up and 20% will move down on index in any given evaluation.

The ICBF conducts evaluations every four months where the bull’s figures are reassessed as additional information is recorded. If a stock bull has a €uro-Star rating of five stars on the replacement index, the reliability of this data may only be 20% to 30%. As a result, if the bull moves down to three stars on a subsequent evaluation, his progeny will also receive lower indexes.

The advantage of using proven high-reliability AI sires to father replacements is that there is much less chance of the figures being re-evaluated downwards to any great extent, so that you have much more confidence that the heifers you breed from him will remain high on the replacement index.

Understanding the figures

Figure 1 (above) shows a €uro-Star report of the highest-ranked bull on the replacement index active bull list – the Angus bull Lanigan Red Deep Canyan ET (ZLL), carried by Bova.

1 This is the bull’s ranking on the replacement index. He has an overall value of €249, broken down into €180 from maternal cow traits and €69 for progeny traits.

2 The reliability of the replacement index is 52%, which is average, but if you are looking for high reliability, then you may need to use bulls with a reliability of 80% or higher on this index.

3 The terminal figure for this bull is €117 with a reliability of 80%, which is high. This means that he is five stars within the Angus breed and four stars across breeds on terminal traits.

4 There are no stars in the calving difficulty section. This bull has a calving difficulty of 2.3%, which is very low across breeds and average within the breed. The reliability behind this is 94%, which is very high. This is worth looking out for when bulling heifers. In terms of calving difficulty, if you aim for 4% or lower for heifers, it should be fine where there is a good reliability behind this. Avoid using bulls with low reliability on calving difficulty on heifers and only use on mature cows with good calving ability.

5 Daughter milk is crucial for replacements. As this bull does not have a huge number of heifers on the ground, the reliability behind the figures remains low, but he is five stars on the index.

6 Daughter calving interval can be important when you are trying to reduce the calving interval of the herd. His daughters are expected to have a calving interval of six days shorter than the average.

Using the index

It is important that you match cows with high star ratings to the high replacement index bulls in order to produce a heifer that will be a four- or five-star on the replacement index. For those buying in heifers, they need to be genotyped four- or five-star to qualify. Likewise for those breeding their own replacements, she must be four or five stars when genotyped. This means that you need to be breeding with confidence. For example, if you are using the five-star Limousin bull Sympa (SYM), he is five stars on the replacement index (€141) with 91% reliability. If you are planning on breeding four-star heifers, then you need to be using him on a cow with that is €10 or more on the index in order to get a heifer that is €75. However, this might be cutting it fine, as if the cow’s index goes down, the heifer may fall short of being a four star in this case. If you are targeting a five-star heifer, the cow will need to be at least €55 on the replacement index.

Genomic bulls

Using genomic or test bulls or bulls with low reliabilities (less than 50%) should be done with caution. There is a good chance that the index for a genomic bull or bull with a low reliability will move upwards or downwards. Therefore, it is important not to put all your eggs in one basket. Genomic bulls often have the highest scores on the index as they are the newest genetics coming through. However, because their figures can change when there are daughter proofs, it is essential that you use several of these bulls to reduce the risk of the figures dropping. The advice by Teagasc and the ICBF is to use a team of five genomic bulls if opting to do so. Otherwise, stick to high reliability-proven sires.

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