The new ranking for young Holstein sires, features some show-stopping figures, made all the more remarkable when the five-yearly base change, which was implemented with this proof run, is considered.

The no. 1 sire is new entry, Genosource Captain (Charl x Sabre x Ahead), which has a genomic Profitable Lifetime Index (£PLI) of £882 reflects his extreme Predicted Transmitting Abilities (PTAs) for production (1016kg milk, 49.1kg fat), combined with excellent maintenance (-14) and leg health. This is demonstrated through a Lameness Advantage +3.0 and a score of +0.6 for the newly introduced Digital Dermatitis Index (see panel).

These figures are particularly impressive in the light of the base change, which knocks £142 off each bull’s £PLI since the last (Dec ’19) index run, as the average is adjusted downwards to reflect the genetic progress made over the past five years (see panel).

Captain ranks over 90 £PLI points ahead of the new entry in second place – FB Kenobi Targaryen (Kenobi x Jedi), which has a PLI of £790. Targaryen is a high protein transmitter (35.9kg, +0.09%), with excellent predicted calf survival (+3.5).

A PLI of £774 is enough to move former top 10 sire, Denovo 15158 Admiral (Torque x Yoder) into third position and he becomes the highest weight of fat transmitter in the top 20 (+50.3kg, +0.24%). Admiral is also predicted to transmit good maintenance (-9) and calving ease (+1.1).

A newcomer since the December run, although made available earlier this year, Westcoast River (Guarantee x Montana) features in fourth position with a PLI of £771. River’s genetic predictions are sky-high for udder health (-29 SCC, -3 Mastitis), while daughter Fertility Index is an impressive +15.6.

Denovo 14566 Crosby now ranks fifth with a PLI of £770 and the best leg health in the top 20 (+3.4 LA, +0.7 DD).

In joint sixth position, Cal-Roy-Al Darbee (PLI £767) is the highest protein transmitter in the top 20 at a massive +41.7kg. He also offers the best Calf Survival Index (+3.8) and Type Merit (TM) at 2.27, under a revamped TM formula which places more emphasis on feet and legs and smaller stature than previously.

Also in sixth was another new entry since December, Aardema Pistolero (Guarantee x Commander), having a PLI of £767 reflects the prediction of long daughter lifespans (+161 days).

Another newcomer, Koepon Raptor (Lawson x Topshot) slots into eighth position, this time offering exceptional milk quality (+0.28% fat, +0.14% protein) with outstanding daughter lifespans (+210 day) and fertility (+14.3). His PLI is £763.

Ninth position is shared at a PLI of £761 by Prismagen Grande Rio and the UK-bred Boghill Glamour, both of which edge up from just outside the top 10. Rio’s maintenance of -19 reflects his daughters’ lower maintenance costs and he also has the best digital dermatitis prediction in the top 50 at +0.8. Meanwhile, Glamour’s notable strength is his daughter fertility (+12.2).

Just outside the top 10

Four further newcomers just outside the top 10 are Blumenfeld Sedona (Skywalker x Apprentice), notable for high TM and milk quality (PLI £760); Bomaz Kettle (Kenobi x Topshot), also increasing milk quality (PLI £755); Denovo 14744 Ginetta (Guarantee x Delta), with a PLI of £746 and Mr Wings Norton (Wings x Nominee), with a PLI of £742.

With breeding companies choosing to launch large numbers of new bulls with this proof run (almost half the top 50 are new releases), UK producers have a wide selection from which to choose. However, as always, they will need to check pedigrees closely to ensure they maintain their herds’ genetic diversity.

“Having so many new bulls certainly gives breeders plenty of choice but that can sometimes feel overwhelming,” said Marco Winters, head of animal genetics for AHDB Dairy.

“I would strongly recommend farmers clearly set their own breeding goals and then use one of the breed societies’ or breeding companies’ proprietary mating programs to help them select bulls which meet their needs. By specifying a limit to minimise increases in inbreeding through these programs, or by using AHDB’s own Inbreeding Checker, farmers can help to maintain genetic diversity through their choice of sires.”

What’s new this proof run?

Five-yearly base change

Genetic indexes are expressed as a comparison to the breed average, which is set at zero. However, assuming the national herd makes genetic progress, the average creeps up over time. So, every five years, the national average is recalculated in the UK and reset to zero. This means all other genetic index figures change in their difference from breed average – although the order in the rankings remains the same. This so-called base change has been carried out with the April 2020 index run, for which the average has been reset to reflect the average genetic merit of cows born in 2015. This has pulled down almost all genetic index figures for all dairy breeds, with the magnitude of the change detailed on the AHDB Dairy website.

For the Holstein, the overall decline in £PLI is £142, meaning each bull’s £PLI declines by this amount purely due to the base change. All of this ensures genetic index figures don’t keep getting higher and higher, moving so far away from the original average it becomes hard to see where a bull stands in relation to the UK’s national herd.

Genomic evaluation system upgrade

When an animal’s genotype is assessed it is done by tracking its DNA through a number of markers, or so-called SNPs. These genetic markers are then analysed by the AHDB and its partners at SRUC-EGENES who are able to interpret them as Predicted Transmitting Abilities (PTAs). The number of markers under scrutiny had, until this proof run, been 43,000. However, in April 2020, the density was upgraded to 80,000 markers which will now be routinely used. This enhanced marker density enables AHDB Dairy to track the genes involved in better performance more closely and to improve our genomic predictions. This fine-tuning has caused some minor reshuffling in the ranking of bulls.

Digital Dermatitis Index

Digital dermatitis has been collected as part of the NBDC’s dairy breed societies’ classification process for many years and has been used as part of the Lameness Advantage calculation since 2018. However, many producers are keen to know which bulls specifically transmit better resistance to digital dermatitis to their daughters, so from this proof run onwards, it will be made available to producers as a standalone index. The Digital Dermatitis Index (DD) is expressed on a scale of about -2% to +2%, with positive figures being desirable. Daughters of a bull with a +2% DD are expected to have 2% fewer cases of digital dermatitis than daughters of a bull whose DD is zero.