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Saturday 21 October 2017

Next Generation study gauges the value of selecting for EBI

Sinead McPartland

The much anticipated Next Generation Herd study recently established at Teagasc Moore-park is finally under way.

The herd, which was set up last year with the purchase of heifers from across the country, comprises just over 160 first lactation Holstein-Friesian cows and almost 50 maiden heifers.

Most of the cows have calved by now. The research study aims to assess the value of selecting for EBI by measuring the cows' performance. For this reason the herd comprises heifers of elite EBI genetics and heifers representative of the national average of animals born in 2011.

Two thirds of the animals, therefore, have an average EBI of €232, putting them firmly inside the top 1pc in the country. The remaining third are those representative of national average – known as control heifers.

These have an EBI of €120. Their average EBI is just higher than the average of heifers born in 2011. All heifers were genomically tested prior to purchase and underwent a most stringent disease-testing regime prior to purchase.

The cows will shortly be randomly assigned across three seasonal grass-based management systems reflecting efficient futuristic seasonal production.

As well as striving to maximise the EBI within the elite herd, the staff at Moorepark are very anxious to maintain genetic diversity.

To ensure the proper disentanglement of sire line effects from EBI effects, it is necessary for the herd to be representative of a wide range of unrelated sires.

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This had implications for the heifers with regard to purchase into the herd. Consequently, the focus was put on identifying the highest EBI daughters available from a wide range of bulls.

Maintaining genetic diversity will also impact on the sire selection policy in the future. Unlike a commercial herd, therefore, a slightly unorthodox approach will be employed in order to meet these somewhat conflicting criteria.

A larger team of bulls than would ordinarily be recommended will be identified for use on the Next Generation Herd.

Sires will be a mixture of new and old and will come from the range of AI stables. A number of the very best of modern Irish genomically selected sires will be utilised alongside some 'old gems' no longer commercially available that have a proven track record for success in our system.

The logic here is to capitalise on the potential to reap huge genetic gains from some of the 'young guns' while at the same time being cautious of the low reliability values of these bulls.

Examples of the young sires that are currently being considered include: KSK, RPA, ZTG, PKK, WLY, PZS, GXY and AKZ, among others.

As mentioned, a limited number of straws from some old timers with high EBI values that have very high reliability (proven success) such as KNW, WAU, CWJ and CBH have been secured for use this spring.

Added to these will be the most promising sires from recent years such as PKK, NFT, BQB, BGJ etc.

To maintain the control group of heifers, sires selected for this group will be in the €140 to €160 EBI range and will comprise highly reliable bulls such as MVI, WDH and KLA.

The Sire Advice programme offered through the ICBF HerdPlus package will be used to assist with the process of allocating these sires to each of the individual females in the herd.

For this purpose the elite and the national average females will be considered as two separate herds.

Proven calving ease (<2pc) will be a critical consideration when choosing sires to be mated to the maiden heifers.

Sinéad McParland is a Teagasc researcher based in the Animal and Grassland research and innovation centre in Moorepark

Irish Independent