Genomic young sires now make up over 40 per cent of all black and white inseminations in the UK, so it’s little surprise to see the young sire list is a growing focus of dairy producers’ attention.

Leading the pack in the AHDB Dairy Profitable Lifetime Index ranking is the Canadian bred Sandy-Valley-I Penmanship who holds convincingly on to his number one position, some 66 £PLI points ahead of his closest rival. This Enforcer son from a Numero Uno dam transmits a remarkable combination of high production with outstanding daughter lifespan (+0.7) and fertility (+12.0), which sees his PLI continue to move upwards and now reach £743. With figures based largely on his own DNA (which always remains static) together with an element of his parents’ performance, it is the latter which has improved over the past few months.

Second ranking Stantons Checkers (Predestine x Freddie) is one of four newcomers to the top 10, making his debut with a PLI of £677, a particularly high percentage fat (+0.25%) and a high Lifespan Index (+0.7). He also scores favourably for maintenance

(-2), indicating his progeny require less feed than average for their own maintenance and he is the highest type transmitter in the top 10.

Climbing to third is De-Su Firewall (PLI £669), another sire with an excellent maintenance index (-9), thanks to daughters which are slightly smaller than average. He combines this with solid production, low somatic cell counts (-25), high lifespan (+0.6) and good daughter fertility (+11.1).

The highest UK-bred sire and from a pure British cow family is Topcroft Pesky Trix who moves into fourth position with a PLI of £660. Featuring solid production and superb fitness, Trix is backed by a family which is chalking up high lifetime yields and maintaining its fertility. Bred by Tom Crawford in his Suffolk herd, Trix has the further attraction of being the first Pesky son to the market. He also weighs in with a Type Merit of 2.17.

Boardshop holds his PLI at £657 and shares fifth place with newcomer, Comestar Loic (Flame x Sudan), whose breeding pattern is notable for its high milk components.

Also new in the top 10 are Apina Nadal in seventh and eighth-ranking De-Su Apex (PLI £652 and £648). Nadal, as a Rocky x Goliath, has a pedigree that’s somewhat different from the norm but comes from a family that has produced several high genomic animals already, including 24th ranking Norman. Apex’s pedigree (Cashcoin x Numero Uno) is more familiar and he is maternal half-brother to Battlecry in 20th position. Apex (PLI £648) has superb transmitting abilities for fitness traits, with very low daughter maintenance (-16), low SCCs (-32) and long lifespans (+0.7).

Rounding off the top 10 are De-Su Octavian (PLI £637) and Amax (PLI £630), who both featured in the top 10 in the last index run in April.

Other new names to watch out for which fall just outside the top 10 are Sonray-Acres PRD Justice (Predestine x Man-O-Man), a bull transmitting good milk quality and low maintenance (-4) and with a PLI of £620; Sandy-Valley-I Picasso (full brother to Penmanship) and with a PLI of £619; and Bush-Bros JC Justify (Jacey x Denim) who is one of the best daughter fertility improvers in the top 25 (+12.6) and also has a PLI of £613.

“The quality of genetics in this August index run is undeniably high, so it comes as no surprise that young sires are growing in importance and popularity,” says Marco Winters, head of genetics for AHDB Dairy. “Farmers are certainly encouraged to use young sires which are capable of bringing qualities to their herds that are harder to come by amongst the daughter-proven sires, but they are always advised to choose their sires with care.

“It’s important not to forget that the reliability of these bulls is still lower than that of the daughter-proven bulls so I’d recommend choosing a group of sires - roughly choosing two young sires in the place of every one proven bull you would traditionally have used.”

A table of the top 20 available Holstein bulls with a genomic index ranked on the latest PLI (August 2015) appears below. Type Merit is supplied by Holstein UK.