Block-calver indexes extended to autumn

A new Autumn Calving Index (£ACI) has been added to that for spring block-calvers, giving a full complement of tailored genetic ranking tools for dairy producers, whatever their management system.

As an across-breed index which is designed to help those who calve in autumn in a block of 12 weeks or less, the index will help producers with their sire selection, whether they are pure- or cross-breeding.

Like the Spring Calving Index (£SCI), the £ACI includes all the traits which make up the existing Profitable Lifetime Index (£PLI), but in slightly different proportions. This reflects the different costs of production, price of milk, and – in some cases – type of cow required under the various systems. 

“All of this means that we now have genetic indexes which are better tailored to help a cross-section of producers, with the main ranking tool, the £PLI, now recommended for herds which calve for all or most of the year,” says Marco Winters, head of animal genetics with AHDB Dairy.

Top bull for autumn calving

Features of this first ever run for £ACI include a domination by Holsteins – a breed renowned for its profit potential under many production systems – and a front-runner in the shape of high daughter fertility transmitter, S-S-I Shamrock Mystic

“The difference between the three genetic indexes which are now running concurrently is subtle and many of the bulls appear high on all three lists,” says Mr Winters. “S-S-I Shamrock Mystic is one such example, which features high in the £PLI, £ACI and £SCI rankings.”

Friesian front-runner for £SCI

For the Spring Calving Index – which, like £PLI, has undergone a subtle reformulation this month – there is a British Friesian front-runner for the first time since the index’s launch.

The number one £SCI bull is Catlane Caleb, whose outstanding daughter fertility helps earn him his leading position.

Alongside a continued domination by the Jersey breed, two New Zealand-bred bulls are also a feature of the top £SCI ranking.

Mr Winters explains that the slight reformulation of £SCI brings an increased emphasis to daughter fertility as well as milk quality.

“As with changes to £PLI, this reflects industry feedback, and a general view amongst grazing based spring calving producers that a greater emphasis was desirable on these two particular features.”

The fact that some bulls, which feature high on both Irish and New Zealand indexes, also do well on the UK block calving indexes is of interest.

“However, it’s important to remember that that these UK indexes have been specifically tailored for UK market conditions and therefore should be the primary screening index when selecting potential service sires,” he says.

It is also vital to note that the Predicted Transmitting Ability (PTA) figures behind the two block calving indexes are not comparable with PTAs used in the calculation of £PLI.


See tables below.

For further information:

N:  Alistair McLaren

T:   024 7647 8970





A table of the top 20 available Holstein bulls with a daughter proof ranked on the latest £PLI (August 2018) appears below. Type Merit is supplied by Holstein UK.

A Welsh language version of this press release is available on request. Please contact Menna Davies on 07875 098173 or

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See tables below.