One of the top milk quality improvers of the Holstein breed, Mr Rubi-Agronaut, again leads the way amongst genomic, young sires in the new AHDB Dairy indexes, with a December 2017 Profitable Lifetime Index (PLI) of £812.

Retaining the position he has held throughout the year, Agronaut transmits fat and protein percentages at +0.22% and +0.09% respectively, and also has the highest Type Merit of the top 20 sires at +3.12. This type score reflects the new emphasis on bulls with smaller stature in Holstein UK’s newly revised Type Merit formula.

Climbing into second place is Claynook Casper (Hang-Time X Bombero). Like all of the top £PLI sires, Casper scores strongly for both daughter fertility (Fertility Index +13.4) and daughter lifespan (LS +0.7 lactations).

VH Balisto Brook holds on to third spot, transmitting a massive weight of fat at +40.5kg and good udder health, with -36 for Somatic Cell Count and -6 for Mastitis.

Fourth ranking is Peak AltaDepot, another strong udder health bull, which also has excellent daughter fertility (+17.6) and the highest Lifespan Index in the breed at +0.9. This indicates his daughters last nearly a full lactation longer, on average, than those of a bull with a zero score for LS – a benefit which will accumulate down the generations.

Former No 1 sire, Westcoast Perseus holds his position in the top five with a PLI of £788 and high protein percentage (+0.11%), and stands ahead of the first brand new bull in the top 10. This new entry, Progenesis Doctor, rates favourably for reducing maintenance feed cost for his daughters (-6) and has a high milk Predicted Transmitting Ability (PTA) at 811kg.

UK-bred Prehen Lancaster is another favourable daughter maintenance transmitter at

-3, reaffirming his position amongst the world’s best. With an good daughter Fertility Index of +17.4, he can also be expected to improve a herd’s reproductive performance.

In equal eighth place is Progenesis Padawan, a high milk bull (956kg), transmitting particularly high protein (32.2kg). Sharing eight position is Leaninghouse Helix which has good all round PTAs and a PLI of £773.

A newcomer to the rankings rounds off the top 10 in the shape of G-DeRuyter AltaNitro. This son of Bacon-Hill Pety Modesty X Morningview MCC Kingboy offers high production and good health across the board, earning a PLI of £757.

Other new entrants with some stand-out figures amongst the top 20 include the high percentage protein improver (+0.13%), NH Sunview Fantastic (Flattop X Balisto) and Cal-Roy-Al Yoda (Jedi X Yoder), transmitting massive production of 1082kg milk with 48.7kg fat and 38.8kg protein.

Commenting on the new figures, Marco Winters, head of animal genetics for AHDB Dairy, says: “Holstein breeders are in a fortunate position to have access to such top quality genetics. However, breeders are reminded, to watch out for increased maintenance feed costs for the taller Holstein bulls.

“Breeders are advised to make their initial selection of bulls based on their £PLIs, but to drill down through the figures to ensure the bulls they choose are suited to the particular needs of their herd.”