Producers calving in a tight block in autumn, with a focus on genetic improvement, are advised to consider basing their sire selection on Autumn Calving Index (£ACI).
Although developed along similar principles to the more commonly used £PLI, the £ACI takes more account of the winter milk price.
It also takes into account the feed costs associated with producing a higher proportion of winter milk and places a greater emphasis on daughter fertility than in year-round calving herds.
These nuances see a slightly different list emerge in the Agriculture and Horticulture Development Board’s (AHDB) August rankings, at the top of which stands Winstar Mendel P.
This bull’s ACI of £719 reflects his exceptional Predicted Transmitting Ability (PTA) for weight of fat and a good Maintenance Index for feed.
Moving into second place is Winstar Graziano (ACI £713), another high milk solids bull, who also transmits lower somatic cell counts.
Peak Mauney ranks third (ACI £705), with very good ratings for both lifespan and daughter fertility.
However, the best daughter fertility bull in the top 20 is Progenesis Wimbledon who ranks fourth, with an ACI of £699.
With an ACI of £693, Aardema Pistolero now ranks fifth, followed by the high reliability sire, Denovo Invictus. This bull now has 2,430 UK milking daughters, and excels for daughter fertility and maintenance.
Denovo 16441 Millennium is a new entry in seventh place with an ACI of £677. He is a high fat transmitter, with good lifespan ratings.
Denovo 14744 Ginetta transmits the highest combined weight of fat and protein in the top 20, only just outperforming ninth placed Bomaz Kettle (ACI £669).
Westcoast Guarantee’s ACI of £668 earns him 10th place – a position he shares with Denovo 16219 Aladdin.
In the Spring Calving Index (£SCI) ranking, Progenesis Wimbledon moves up one place to become the new leader. His SCI of £601 is in part due to excellent daughter fertility.
Winstar Mendel P takes second place (SCI £599), closely followed by Denovo Invictus (SCI £598).
Fourth placed is Winstar Graziano (SCI £591), ahead of Denovo 7921 Atrium (SCI £579) in fifth.
Atrium now has over 5,000 UK daughters milking, and is proving to breed fertile cows which are of a smaller stature, which contributes to a very favourable Maintenance Index.
Positions six to eight are occupied by Peak Mauney (SCI £566), Aardema Pistolero (SCI £563), debutant, Denovo 16441 Millennium (SCI £559) and Westcoast Guarantee (SCI £554).
These Holsteins stand just ahead of a Jersey sire on these across-breed rankings, with VJ NR Hauggaard Nibali Nibiru taking 10th position.
This bull’s exceptional transmission of fat and protein – even for his breed – accentuates his suitability for spring block calving herds.
Marco Winters, Head of Animal Genetics at AHDB, urges producers to favour these indexes if they are calving in a block of up to 12 weeks – either grazing for £SCI or winter feeding for £ACI – particularly if they are using mixed breeds.
“Both £SCI and £ACI have been developed as across breed indexes which allows producers to directly compare one breed with another, when specifically using these rankings.”
However, he warns producers not to compare the lists with each other, or with £PLI or its components.
“Each of these indexes is calculated on its own genetic base, which means they must only be compared within their relevant group.”
